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Jul 2010

Volume 28, Issue 4, pp. L5-1028

Issue Cover Spotlight Figure

J. Vac. Sci. Technol. A 28, 1010 (2010); http://dx.doi.org/10.1116/1.3271148 (8 pages)

A. Michalkova and J. Leszczynski
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Microplasma-assisted growth of colloidal Ag nanoparticles for point-of-use surface-enhanced Raman scattering applications

Fang-Chia Chang, Carolyn Richmonds, and R. Mohan Sankaran

J. Vac. Sci. Technol. A 28, L5 (2010); http://dx.doi.org/10.1116/1.3428708 (4 pages) | Cited 13 times

Online Publication Date: 15 June 2010

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The authors present a facile, rapid, one-step process to synthesize Ag nanoparticle for surface-enhanced Raman scattering (SERS) applications. Aqueous metal ions are electrochemically reduced by a microplasma to nucleate nanoparticles at ambient conditions (room temperature and atmospheric pressure) without any chemical reducing agents or stabilizer molecules. The nanoparticles are characterized by UV-visible absorbance and transmission electron microscopy, and found to be spherical, crystalline, and uniform with an average diameter of approximately 10 nm. Preparing nanoparticles with only a target analyte molecule present in solution allows intimate interaction between the metal particle surface and the analyte. Raman analysis shows that the scattered signal from a test molecule, crystal violet, is dependent on the process time and maximized after nanoparticles are grown for 20 min. This optimal SERS signal is large and permits detection of an analyte down to 10−10M concentrations.
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81.07.Bc Nanocrystalline materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.30.Er Solid metals and alloys
78.40.Kc Metals, semimetals, and alloys
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
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Correlation of structure and hardness of rf magnetron sputtered silicon carbonitride films

A. S. Bhattacharyya, S. K. Mishra, and S. Mukherjee

J. Vac. Sci. Technol. A 28, 505 (2010); http://dx.doi.org/10.1116/1.3420430 (5 pages) | Cited 2 times

Online Publication Date: 15 June 2010

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Ternary nanocomposite silicon carbonitride (SiCN) ceramic coatings have shown potential for wear resistance, oxidation resistance, hardness, tunable band gap, and chemical inertness applications. A systematic investigation on the deposition of SiCN nanocomposite coatings by sputtering under varying deposition conditions such as chamber pressure, substrate temperature by structural, nanoindentation, and microstructural studies of optimized condition has been presented. Significant role of different deposition parameter on the mechanical and structural properties were observed. The structural characterizations of the coatings were carried out using Fourier transformed infra red (FTIR), transmission electron microscopy, Raman spectroscopy, and field emission scanning electron microscope. An increase in argon-nitrogen pressure in the range of 1–5 Pa led to lowering of particle size and surface smoothening and growth of hard phases of β-C3N4 and β-Si3N4. An increase in substrate temperature from room temperature to 500 °C led to nucleation and growth of hard phases of β-C3N4 and Si3N4 in the amorphous SiCN matrix. The nanoindentation studies showed the variation in hardness and Young’s modulus from 8 to 22 GPa and from 100 to 240 GPa, respectively, dependent on the deposition conditions. The FTIR studies confirmed the presence of CN, SiN, SiSi, SiO, and SiC in different films.
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81.15.Cd Deposition by sputtering
78.30.Hv Other nonmetallic inorganics
62.20.de Elastic moduli
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness

Surface analysis of polyimide bombarded by charged water droplets

Kenzo Hiraoka, Yuji Sakai, and Yoshitoki Iijima

J. Vac. Sci. Technol. A 28, 510 (2010); http://dx.doi.org/10.1116/1.3420465 (5 pages) | Cited 7 times

Online Publication Date: 15 June 2010

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500 eV Ar+ ion impact and the electrospray droplet impact (EDI), in which the charged electrospray water droplets are introduced in vacuum, accelerated and allowed to impact the sample, are applied for etching of polyimide (PI). After the bombardment, x-ray photoelectron spectroscopy (XPS) was applied to the surface analysis. Although oxygen and nitrogen are selectively etched by Ar+ ion impact, the XPS spectra did not change with prolonged charged water droplets irradiation, i.e., EDI is capable of shallow surface etching for PI with little damage of the sample after irradiation.
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81.65.Cf Surface cleaning, etching, patterning
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
79.60.Fr Polymers; organic compounds

Deposition of aluminum-doped zinc oxide thin films for optical applications using rf and dc magnetron sputter deposition

Kousik Sivakumar and S. M. Rossnagel

J. Vac. Sci. Technol. A 28, 515 (2010); http://dx.doi.org/10.1116/1.3425640 (8 pages) | Cited 1 time

Online Publication Date: 15 June 2010

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Aluminum-doped zinc oxide films were deposited by dc and rf magnetron sputtering from ZnO(98%)Al2O3(2%) target at room temperature on silicon and glass substrates under a variety of process conditions with the goal of attaining the highest transmittance and lowest resistivity for photovoltaic applications. The magnetron power and pressure were varied. For many dielectric deposition systems, added oxygen is necessary to achieve the appropriate stoichiometry. The effect of oxygen on film properties was then studied by varying the oxygen partial pressure from 1.5×10−5 to 4.0×10−5 T at a constant Ar pressure, with the result that any added oxygen was deleterious. Films deposited under power, pressure, and low-oxygen conditions were then characterized for electrical and optical properties. Following this, the dc and rf sputtered films were annealed at up to 400 °C seconds using rapid thermal annealing (RTA), and the influence of annealing on resistivity, transmittance, band gap, as well as grain growth and stress was studied. The effect of RTA was immediate and quite significant on dc films while the effect on rf films was not as profound. As-deposited rf films had a higher average transmittance (87%) and lower resistivity (5.5×10−4 Ω cm) compared to as-deposited dc films (84.2% and 8.9×10−4 Ω cm). On the other hand, after RTA at 400 °C for 60 s, dc films exhibited better average transmittance (92.3%) and resistivity (2.9×10−4 Ω cm) than rf films (90.7% and 4.0×10−4 Ω cm). The band gap of dc films increased from 3.55 to 3.80 eV while that of rf films increased from 3.76 to 3.85 eV. Finally, dc and rf films were textured in 0.1% HCl and compared to U-type Asahi glass for resistivity and transmittance.
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81.15.Cd Deposition by sputtering
68.55.ag Semiconductors
78.66.Hf II-VI semiconductors
73.61.Ga II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
71.20.Nr Semiconductor compounds

Properties of thin N-type Yb0.14Co4Sb12 and P-type Ce0.09Fe0.67Co3.33Sb12 skutterudite layers prepared by laser ablation

Radek Zeipl, Jarmila Walachová, Jan Lorinčík, Sergey Leshkov, Monika Josieková, Miroslav Jelínek, Tomáš Kocourek, Karel Jurek, Jiří Navrátil, Ludvík Beneš, and Tomáš Plecháček

J. Vac. Sci. Technol. A 28, 523 (2010); http://dx.doi.org/10.1116/1.3425803 (5 pages) | Cited 2 times

Online Publication Date: 15 June 2010

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The properties of thin thermoelectric layers (about 60 nm in thickness) prepared by pulsed laser deposition are presented. Hot pressed targets were made from “middle” temperature range thermoelectric bulk materials with the potential high figure of merit ZT. P-type and N-type layers were prepared from Yb0.19Co4Sb12 and Ce0.1Fe0.7Co3.3Sb12 targets, respectively. The thin films were deposited on quartz glass substrates using KrF excimer laser. The individual layers were prepared by applying different laser beam energy densities (2 or 3 J cm−2) at several substrate temperatures (200, 250, or 300 °C). Crystallinity and composition of the layers were examined by x-ray diffraction and wavelength dispersive analysis, respectively. Homogeneity of Yb across a surface of the Yb filled film was explored by secondary ion mass spectrometry. The thermoelectric properties, the Seebeck coefficient, the electrical resistivity, and the power factor, for the best prepared P and N layer are presented in the temperature range from 300 to 500 K.
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72.15.Jf Thermoelectric and thermomagnetic effects
81.07.Bc Nanocrystalline materials
81.16.Mk Laser-assisted deposition
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
72.80.Ga Transition-metal compounds

Investigation on structure and properties of arc-evaporated HfAlN hard coatings

R. Franz, C. Mitterer, M. Lechthaler, and C. Polzer

J. Vac. Sci. Technol. A 28, 528 (2010); http://dx.doi.org/10.1116/1.3425804 (8 pages) | Cited 3 times

Online Publication Date: 16 June 2010

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HfAlN hard coatings were synthesized by cathodic arc evaporation from Hf0.75Al0.25 targets at different bias voltages and N2 pressures. Structural investigations by x-ray diffraction (XRD) revealed the formation of a face-centered cubic (fcc) structure with a change in the preferred orientation depending on the energetic growth conditions. This change in the crystal structure did not significantly influence the mechanical properties, e.g., hardness, where values ranging from 24 to 26 GPa were measured. The obtained fcc phase is stable up to 1000 °C as no significant changes in the crystal structure could be observed after annealing in vacuum. Similar experiments in ambient air and subsequent analysis of the coatings by XRD and Raman spectroscopy revealed an onset temperature for oxidation in the range of 700–800 °C and the formation of monoclinic HfO2 as the dominating oxide phase. Ball-on-disk tests at different temperatures were performed in order to evaluate the tribological properties. The coefficient of friction ranged from 0.8 to 1.2 depending on the testing temperature while the best wear performance was obtained in the temperature range of 300–500 °C.
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81.05.Bx Metals, semimetals, and alloys
81.40.Pq Friction, lubrication, and wear
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.65.Mq Oxidation
68.55.A- Nucleation and growth
81.15.Dj E-beam and hot filament evaporation deposition

Growth of epitaxial iron nitride ultrathin film on zinc-blende gallium nitride

J. Pak, W. Lin, K. Wang, A. Chinchore, M. Shi, D. C. Ingram, A. R. Smith, K. Sun, J. M. Lucy, A. J. Hauser, and F. Y. Yang

J. Vac. Sci. Technol. A 28, 536 (2010); http://dx.doi.org/10.1116/1.3425805 (5 pages) | Cited 2 times

Online Publication Date: 16 June 2010

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The authors report the growth of iron nitride on zinc-blende gallium nitride using molecular beam epitaxy. First, zinc-blende GaN is grown on a magnesium oxide substrate having (001) orientation; second, an ultrathin layer of FeN is grown on top of the GaN layer. In situ reflection high-energy electron diffraction is used to monitor the surface during growth, and a well-defined epitaxial relationship is observed. Cross-sectional transmission electron microscopy is used to reveal the epitaxial continuity at the gallium nitride-iron nitride interface. Surface morphology of the iron nitride, similar to yet different from that of the GaN substrate, can be described as plateau valley. The FeN chemical stoichiometry is probed using both bulk and surface sensitive methods, and the magnetic properties of the sample are revealed.
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68.55.A- Nucleation and growth
75.30.Cr Saturation moments and magnetic susceptibilities
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.bt Other materials
68.55.J- Morphology of films

Reactive magnetron cosputtering of hard and conductive ternary nitride thin films: Ti–Zr–N and Ti–Ta–N

G. Abadias, L. E. Koutsokeras, S. N. Dub, G. N. Tolmachova, A. Debelle, T. Sauvage, and P. Villechaise

J. Vac. Sci. Technol. A 28, 541 (2010); http://dx.doi.org/10.1116/1.3426296 (11 pages) | Cited 12 times

Online Publication Date: 16 June 2010

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Ternary transition metal nitride thin films, with thickness up to 300 nm, were deposited by dc reactive magnetron cosputtering in Ar–N2 plasma discharges at 300 °C on Si substrates. Two systems were comparatively studied, Ti–Zr–N and Ti–Ta–N, as representative of isostructural and nonisostructural prototypes, with the aim of characterizing their structural, mechanical, and electrical properties. While phase-separated TiN–ZrN and TiN–TaN are the bulk equilibrium states, Ti1−xZrxN and Ti1−yTayN solid solutions with the Na–Cl (B1-type) structure could be stabilized in a large compositional range (up to x = 1 and y = 0.75, respectively). Substituting Ti atoms by either Zr or Ta atoms led to significant changes in film texture, microstructure, grain size, and surface morphology, as evidenced by x-ray diffraction, x-ray reflectivity, and scanning electron and atomic force microscopies. The ternary Ti1−yTayN films exhibited superior mechanical properties to Ti1−xZrxN films as well as binary compounds, with hardness as high as 42 GPa for y = 0.69. All films were metallic, the lowest electrical resistivity ρ ∼ 65 μΩ cm being obtained for pure ZrN, while for Ti1−yTayN films a minimum was observed at y ∼ 0.3. The evolution of the different film properties is discussed based on microstructrural investigations.
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81.15.Cd Deposition by sputtering
81.40.Rs Electrical and magnetic properties related to treatment conditions
73.61.At Metal and metallic alloys
68.60.Bs Mechanical and acoustical properties
68.55.jm Texture
68.55.aj Insulators

Surface morphology of Kr+-polished amorphous Si layers

A. J. R. van den Boogaard, E. Louis, E. Zoethout, S. Müllender, and F. Bijkerk

J. Vac. Sci. Technol. A 28, 552 (2010); http://dx.doi.org/10.1116/1.3428545 (7 pages) | Cited 5 times

Online Publication Date: 16 June 2010

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The surface morphology of low-energy Kr+-polished amorphous Si layers is studied by topographical methods as a function of initial substrate roughness. An analysis in terms of power spectral densities reveals that for spatial frequencies 2×10−2–2×10−3 nm−1, the layers that are deposited and subsequently ion polished reduce the initial substrate roughness to a rms value of 0.1 nm at the surface. In this system, the observed dominant term in linear surface relaxation, proportional to the spatial frequency, is likely to be caused by the combined processes of (a) ion-induced viscous flow and (b) annihilation of (subsurface) free volume during the ion-polishing treatment. Correspondingly, a modification of the generally assumed boundary conditions, which imply strict surface confinement of the ion-induced viscous flow mechanism, is proposed. Data on surface morphology are in agreement with the optical response in extreme ultraviolet from a full Mo/Si multilayered system deposited onto the modified substrates.
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81.65.Ps Polishing, grinding, surface finishing
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Investigation of the surface chemical and electronic states of pyridine-capped CdSe nanocrystal films after plasma treatments using H2, O2, and Ar gases

Seok-Joo Wang, Hyuncheol Kim, Hyung-Ho Park, Young-Su Lee, Hyeongtag Jeon, and Ho Jung Chang

J. Vac. Sci. Technol. A 28, 559 (2010); http://dx.doi.org/10.1116/1.3431079 (5 pages)

Online Publication Date: 16 June 2010

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Surface chemical bonding and the electronic states of pyridine-capped CdSe nanocrystal films were evaluated using x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy before and after plasma treatments using H2, O2, and Ar gases from the viewpoint of studying the effects of surface capping organic molecules and surface oxidation. Surface capping organic molecules could be removed during the plasma treatment due to the chemical reactivity, ion energy transfer, and vacuum UV (VUV) of the plasma gases. With O2 plasma treatment, surface capping organic molecules were effectively removed but substantial oxidation of CdSe occurred during the plasma treatment. The valence band maximum energy (EVBM) of CdSe nanocrystal films mainly depends on the apparent size of pyridine-capped CdSe nanocrystals, which controls the interparticle distance, and also on the oxidation of CdSe nanocrystals. Cd-rich surface in O2 and H2 plasma treatments partially would compensate for the decrease in EVBM. After Ar plasma treatment, the smallest value of EVBM resulted from high VUV photon flux, short wavelength, and ion energy transfer. The surface bonding states of CdSe had a strong influence on the electronic structure with the efficient strip of capping molecules as well as different surface oxidations and surface capping molecule contents.
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81.65.Mq Oxidation
81.16.-c Methods of micro- and nanofabrication and processing
73.20.At Surface states, band structure, electron density of states
82.40.-g Chemical kinetics and reactions: special regimes and techniques
79.60.-i Photoemission and photoelectron spectra
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.55.ag Semiconductors
61.46.-w Structure of nanoscale materials
71.20.Nr Semiconductor compounds
78.66.Hf II-VI semiconductors

Making modified fluoropolymer films with low surface energy

Xiangdong Ye, Yugang Duan, Yucheng Ding, and Hongzhong Liu

J. Vac. Sci. Technol. A 28, 564 (2010); http://dx.doi.org/10.1116/1.3435329 (4 pages)

Online Publication Date: 16 June 2010

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A technique of using commercial polymers and additive to fabricate modified fluoropolymer films with low surface energy is proposed. A small amount of the additive can increase the oleophobic behavior of the fluoropolymer and so reduce its surface energy remarkably. The modified fluoropolymer films not only possess low surface energy and are solvent resistant but also have a high modulus. By a simple cast-molding process, both three-dimensional micropillars and complex letters with 100 nm linewidth can be replicated in the modified fluoropolymer films. Moreover, in the authors’ experiment, the modified fluoropolymer film has shown its replicating competence for replicating high-aspect-ratio sub-30 nm structures.
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81.16.-c Methods of micro- and nanofabrication and processing
61.41.+e Polymers, elastomers, and plastics
68.03.Cd Surface tension and related phenomena
68.35.Md Surface thermodynamics, surface energies
81.16.Hc Catalytic methods
65.40.gp Surface energy

Lithium phosphorus oxynitride solid-state thin-film electrolyte deposited and modified by bias sputtering and low temperature annealing

K.-F. Chiu, C. C. Chen, K. M. Lin, C. C. Lo, H. C. Lin, W.-H. Ho, and C. S. Jiang

J. Vac. Sci. Technol. A 28, 568 (2010); http://dx.doi.org/10.1116/1.3435330 (5 pages) | Cited 2 times

Online Publication Date: 16 June 2010

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Amorphous lithium phosphorus oxynitride (LiPON) solid-state thin-film electrolyte has been deposited and characterized. The thin films were prepared by rf magnetron sputtering under various substrate biases. By fabricating under different substrate biases and applying low temperature annealing (473 K), the properties of the LiPON thin-film electrolytes and the electrolyte/cathode interfaces were modified. The ionic conductivity as high as 9.4×10−4 S m−1 can be obtained by depositing at optimal bias. The performances of the consequently fabricated SnO2/LiPON/LiMn2O4 all-solid-state lithium ion thin-film batteries were improved using the bias sputtering technique, due to the enhanced the ionic conductivity and uniform interface.
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82.45.Gj Electrolytes
81.15.Cd Deposition by sputtering
66.30.H- Self-diffusion and ionic conduction in nonmetals
68.55.A- Nucleation and growth
81.40.Gh Other heat and thermomechanical treatments

Safely mounting glass viewports to elastomer sealed vacuum flanges

Patrick J. Abbott and Brian Scace

J. Vac. Sci. Technol. A 28, 573 (2010); http://dx.doi.org/10.1116/1.3442803 (5 pages) | Cited 1 time

Online Publication Date: 17 June 2010

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Elastomer sealed vacuum flanges rely on especially sized elastomer O-rings and corresponding grooves to make an air-tight seal. Depending on the materials being sealed to one another, the O-ring/groove sealing mechanism may be designed for a specific percentage compression of the O-ring at the point of flange-to-flange contact. In the case of a glass viewport being sealed to a metal flange, however, direct contact between the glass and a mating metallic flange may produce stresses in the glass that can lead to failure during system evacuation or while the system is under vacuum. In this article, the authors first review fundamentals of safe O-ring seal construction that the reader will find useful when designing or inspecting viewports meant for vacuum systems. We then discuss an especially constructed adapter flange that allows the safe sealing of a 20 cm diameter glass viewport to an aluminum O-ring flange that was originally designed for a typical metal flange-to-metal flange seal. Factors affecting the strength of glass are discussed, and calculations for maximum deflection under load and safe glass window thickness are presented.
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89.20.Kk Engineering

Sensitivity enhancement in hydrogen permeation measurements

Vincenc Nemanič, Bojan Zajec, and Marko Žumer

J. Vac. Sci. Technol. A 28, 578 (2010); http://dx.doi.org/10.1116/1.3442804 (5 pages) | Cited 3 times

Online Publication Date: 17 June 2010

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Permeation of hydrogen isotopes from the upstream pressure through a membrane into high vacuum at elevated temperatures is a challenging task for vacuum technology, especially when very low fluxes must be determined. Geometrical and mechanical constraints set an engineering issue since the ultimate tightness of the seals at high temperature must be preserved. Recording the steady permeation flux and its transients requires high sensitivity and stability of the gauges. It is anyhow far more challenging to suppress the hydrogen background outgassing flux to the level when it represents only a fraction of the permeation flux. The authors present an innovative permeation cell design that results in efficient hydrogen background suppression. When implemented in an all-metal UHV system, low permeation flux density of hydrogen down to j ∼ 10−9 mbar L/(cm2 s) could be measured on disk-shaped membranes having an area of 8.4 cm2.
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82.39.Wj Ion exchange, dialysis, osmosis, electro-osmosis, membrane processes
07.30.-t Vacuum apparatus
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Thickness inhomogeneities and growth mechanisms of GaP heteroepitaxy by organometallic chemical vapor deposition

X. Liu and D. E. Aspnes

J. Vac. Sci. Technol. A 28, 583 (2010); http://dx.doi.org/10.1116/1.3442805 (7 pages) | Cited 1 time

Online Publication Date: 17 June 2010

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The authors report comparative studies of the deposition of GaP on (001) GaAs, as-polished (001)Si, SiO2-coated (001)Si, nanoscopically roughened (001)Si, and polycrystalline GaP surfaces by organometallic chemical vapor deposition using trimethylgallium (TMG) and phosphine (PH3) sources. The thicknesses of the GaP films increase or decrease exponentially toward the edge of wafers. This functional dependence implies one-dimensional gas-phase diffusion of a reactive species, possibly H–P = Ga–CH3, generated by heterogeneous catalysis according to the reactivity of the different surfaces to the decomposition of PH3. Deposition on (001)Si depends on the type of nanoscopic roughness of the substrate.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.55.ag Semiconductors
68.55.jd Thickness
68.35.Fx Diffusion; interface formation

Epitaxial growth and chemical lift-off of GaInN/GaN heterostructures on c- and r-sapphire substrates employing ZnO sacrificial templates

H. F. Liu, W. Liu, and S. J. Chua

J. Vac. Sci. Technol. A 28, 590 (2010); http://dx.doi.org/10.1116/1.3443220 (5 pages) | Cited 9 times

Online Publication Date: 17 June 2010

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The authors report epitaxial growth of GaInN/GaN heterostructures on ZnO/c-sapphire and ZnO/r-sapphire substrates by using metal-organic chemical-vapor deposition and chemical lift-off by etching away the ZnO templates. Using a black-wax technique and a vapor wax-elimination method, they demonstrate a 10×10 mm2 crack-free lift-off of GaInN/GaN from the c-sapphire substrate followed by bonding to a glass holder. On the ZnO/r-sapphire substrate, with the same lift-off processing, the GaInN/GaN was regularly cracked along its c-axis and the cracking is independent of the etching rate (controlled by the solution density). The cracking mechanism is investigated and discussed based on the x-ray diffraction and Raman-scattering characterizations before and after lift-off.
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68.55.A- Nucleation and growth
78.30.Fs III-V and II-VI semiconductors
73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Growth, electrical, and optical properties of nanocrystalline VO2 (011) thin films prepared by thermal oxidation of magnetron sputtered vanadium films

Zhenfei Luo, Zhiming Wu, Xiangdong Xu, Tao Wang, and Yadong Jiang

J. Vac. Sci. Technol. A 28, 595 (2010); http://dx.doi.org/10.1116/1.3443562 (5 pages) | Cited 1 time

Online Publication Date: 17 June 2010

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Nanocrystalline vanadium dioxide (VO2) thin films were prepared on glass substrates at different deposition temperatures by oxidizing sputtered vanadium films. Atomic force microscope, x-ray diffraction, and Raman scattering were employed to characterize the films. It was confirmed that low deposition temperature resulted in improving oxygen atom diffusion and VO2 nanograin growth in the thermal oxidation process. Investigation of the electrical properties revealed that the amplitude of semiconductor-metal transition and transition temperature decreased, whereas the Hall mobility and carrier concentration increased as the deposition temperature elevated. Optical investigations were carried out in the ultraviolet-visible-near-infrared region. Narrow optical band gaps were observed in these films.
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68.55.aj Insulators
81.07.Bc Nanocrystalline materials
81.15.Cd Deposition by sputtering
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics
73.61.Ng Insulators

Crucible aperture: An effective way to reduce source oxidation in oxide molecular beam epitaxy process

Yong-Seung Kim, Namrata Bansal, and Seongshik Oh

J. Vac. Sci. Technol. A 28, 600 (2010); http://dx.doi.org/10.1116/1.3449051 (3 pages) | Cited 2 times

Online Publication Date: 17 June 2010

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Growing multielemental complex-oxide structures using a molecular beam epitaxy (MBE) technique requires precise control of each source flux. However, when the component elements have significantly different oxygen affinities, maintaining stable fluxes for easily oxidizing elements is challenging because of the source oxidation problem. Here, using Sr as a test source, the authors show that a crucible aperture insert scheme significantly reduces the source oxidation in an oxide-MBE environment. The crucible aperture insert was shaped like a disk with a hole at the center and was mounted inside the crucible; it blocks most of the oxygen species coming to the source, thus reducing the source oxidation. However, the depth of the aperture disk was critical for its performance; an ill-positioned aperture could make the flux stability even worse. With an optimally positioned aperture insert, the crucible exhibited more than four times improvement in Sr flux stability, compared to a conventional, nonapertured crucible.
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07.30.-t Vacuum apparatus

Numerical analysis of the Poiseuille flow and the thermal transpiration of a rarefied gas through a pipe with a rectangular cross section based on the linearized Boltzmann equation for a hard sphere molecular gas

Toshiyuki Doi

J. Vac. Sci. Technol. A 28, 603 (2010); http://dx.doi.org/10.1116/1.3449056 (10 pages) | Cited 5 times

Online Publication Date: 18 June 2010

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Poiseuille flow and the thermal transpiration of a rarefied gas through a long straight pipe with a rectangular cross section are analyzed numerically based on the linearized Boltzmann equation for a hard sphere molecular gas. A deterministic numerical analysis based on the finite difference is carried out, where the collision integral is evaluated with the aid of the numerical kernel method [ Y. Sone et al., Phys. Fluids A 1, 363 (1989) ]. The numerical solution, the mass flow rate as well as the macroscopic variables, is presented and discussed for a wide range of the Knudsen number and various aspect ratios of the cross section.
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47.45.-n Rarefied gas dynamics
47.60.Dx Flows in ducts and channels
47.15.Rq Laminar flows in cavities, channels, ducts, and conduits
47.11.Bc Finite difference methods

Time-resolved Fourier transform infrared spectroscopy of the gas phase during atomic layer deposition

Brent A. Sperling, William A. Kimes, James E. Maslar, and Pamela M. Chu

J. Vac. Sci. Technol. A 28, 613 (2010); http://dx.doi.org/10.1116/1.3455187 (9 pages) | Cited 4 times

Online Publication Date: 24 June 2010

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In this work, a Fourier transform infrared spectroscopy-based method is developed to measure the gas-phase dynamics occurring during atomic layer deposition. This new technique is demonstrated during the deposition of hafnium oxide using tetrakis(ethylmethylamido)hafnium and water vapor. The repeatability of the deposition process is utilized to signal average across multiple cycles. This approach required synchronizing the precursor injection pulses with the moving mirror of the spectrometer. The system as implemented in this work achieves spectra with a time resolution of ≈ 150 ms, but better resolution can be easily obtained. Using this technique, the authors are able to optically measure transients in the molecular number densities of the precursors and product that are the effects of mass transport and surface reactions.
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78.30.Hv Other nonmetallic inorganics
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.47.D- Time resolved spectroscopy (>1 psec)
68.55.at Other materials
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Identification at high mass resolution of the positive ion at m/z 19 produced by electron-stimulated desorption: F+ (rather than H3O+)

Peter Williams and Klaus Franzreb

J. Vac. Sci. Technol. A 28, 622 (2010); http://dx.doi.org/10.1116/1.3420442 (3 pages)

Online Publication Date: 24 June 2010

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Abstract Unavailable
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68.43.Rs Electron stimulated desorption

Simple flash evaporator for making thin films of compounds

M. Hemanadhan, Ch. Bapanayya, and S. C. Agarwal

J. Vac. Sci. Technol. A 28, 625 (2010); http://dx.doi.org/10.1116/1.3443567 (2 pages) | Cited 5 times

Online Publication Date: 24 June 2010

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A simple and compact arrangement for flash evaporation is described. It uses a cell phone vibrator for powder dispensing that can be incorporated into a vacuum deposition chamber without any major alterations. The performance of the flash evaporation system is checked by making thin films of the optical memory chalcogenide glass Ge2Sb2Te5 (GST). Energy dispersive x-ray analysis shows that the flash evaporation preserves the stoichiometry in thin films.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Hd Other semiconductors
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
68.55.ag Semiconductors
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Ultraviolet curing adhesive-based optical fiber feedthrough for ultrahigh vacuum systems

J.-F. Clément, D. Bacquet, and P. Szriftgiser

J. Vac. Sci. Technol. A 28, 627 (2010); http://dx.doi.org/10.1116/1.3448023 (2 pages) | Cited 2 times

Online Publication Date: 24 June 2010

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Abstract Unavailable
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
42.81.Wg Other fiber-optical devices
42.70.Jk Polymers and organics
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Preface

Gerald Lucovsky, Editor-in-Chief, JVST

J. Vac. Sci. Technol. A 28, 632 (2010); http://dx.doi.org/10.1116/1.3453730 (1 page)

Online Publication Date: 29 June 2010

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Abstract Unavailable
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81.16.-c Methods of micro- and nanofabrication and processing
01.10.Fv Conferences, lectures, and institutes
back to top Applied Surface Science

Surface analyses of electropolished niobium samples for superconducting radio frequency cavity

P. V. Tyagi, M. Nishiwaki, T. Saeki, M. Sawabe, H. Hayano, T. Noguchi, and S. Kato

J. Vac. Sci. Technol. A 28, 634 (2010); http://dx.doi.org/10.1116/1.3382312 (5 pages)

Online Publication Date: 29 June 2010

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The performance of superconducting radio frequency niobium cavities is sometimes limited by contaminations present on the cavity surface. In the recent years extensive research has been done to enhance the cavity performance by applying improved surface treatments such as mechanical grinding, electropolishing (EP), chemical polishing, tumbling, etc., followed by various rinsing methods such as ultrasonic pure water rinse, alcoholic rinse, high pressure water rinse, hydrogen per oxide rinse, etc. Although good cavity performance has been obtained lately by various post-EP cleaning methods, the detailed nature about the surface contaminants is still not fully characterized. Further efforts in this area are desired. Prior x-ray photoelectron spectroscopy (XPS) analyses of EPed niobium samples treated with fresh EP acid, demonstrated that the surfaces were covered mainly with the niobium oxide (Nb2O5) along with carbon, in addition a small quantity of sulfur and fluorine were also found in secondary ion mass spectroscopy (SIMS) analysis. In this article, the authors present the analyses of surface contaminations for a series of EPed niobium samples located at various positions of a single cell niobium cavity followed by ultrapure water rinsing as well as our endeavor to understand the aging effect of EP acid solution in terms of contaminations presence at the inner surface of the cavity with the help of surface analytical tools such as XPS, SIMS, and scanning electron microscope at KEK.
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81.65.-b Surface treatments
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
85.25.-j Superconducting devices
84.30.Jc Power electronics; power supply circuits
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
79.60.-i Photoemission and photoelectron spectra

Charging/discharging dynamics of CdS and CdSe films under photoillumination using dynamic x-ray photoelectron spectroscopy

Hikmet Sezen and Sefik Suzer

J. Vac. Sci. Technol. A 28, 639 (2010); http://dx.doi.org/10.1116/1.3289319 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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Thin films of CdS and CdSe are deposited on HF-cleaned SiO2/Si substrates containing ∼ 5 nm thermally grown silicon oxide. x-ray photoelectron spectroscopy (XPS) data of these films are collected in a dynamic mode, which is based on recording the spectrum under modulation with an electrical signal in the form of ±10 V square-wave pulses. Accordingly, all peaks are twined and shifted with respect to the grounded spectrum. The binding energy difference between the twinned peaks of a dielectric system has a strong dependence on the frequency of the electrical stimuli. Therefore, dynamic XPS provides a means to extract additional properties of dielectric materials, such as effective resistance and capacitance. In this work, the authors report a new advancement to the previous method, where they now probe a photodynamic process. For this reason, photoillumination is introduced as an additional form of stimulus and used to investigate the combined optical and electrical response of the photoconductive thin films of CdS and CdSe using dynamic XPS.
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79.60.-i Photoemission and photoelectron spectra
72.40.+w Photoconduction and photovoltaic effects
78.56.-a Photoconduction and photovoltaic effects
78.66.Hf II-VI semiconductors
73.61.Ga II-VI semiconductors

Hot-electron transport studies of the Ag/Si(001) interface using ballistic electron emission microscopy

J. J. Garramone, J. R. Abel, I. L. Sitnitsky, and V. P. LaBella

J. Vac. Sci. Technol. A 28, 643 (2010); http://dx.doi.org/10.1116/1.3397795 (4 pages) | Cited 3 times

Online Publication Date: 29 June 2010

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Ballistic electron emission microscopy has been utilized to investigate the hot-electron transport properties of the Ag/Si(001) Schottky diode utilizing metal films deposited both in situ and ex situ. The Schottky barrier heights are measured to be 0.57±0.02 and 0.59±0.02 eV for the ex situ and in situ depositions, respectively. The metal overlayers demonstrate typical Volmer–Weber growth when deposited on the Si(001) semiconducting substrate, as seen in the scanning tunneling microscopy images. An enhancement in hot-electron transmission is measured for the in situ deposited metal films when compared to the ex situ films.
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85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices
72.20.Ht High-field and nonlinear effects
73.61.At Metal and metallic alloys

Ultrashort pulse laser ablation for depth profiling of bacterial biofilms

Slobodan Milasinovic, Yaoming Liu, Gerald L. Gasper, Youbo Zhao, Joanna L. Johnston, Robert J. Gordon, and Luke Hanley

J. Vac. Sci. Technol. A 28, 647 (2010); http://dx.doi.org/10.1116/1.3397736 (5 pages) | Cited 3 times

Online Publication Date: 29 June 2010

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Sample ablation by pulsed lasers is one option for removing material from a sample surface for in situ depth profiling during imaging mass spectrometry, but ablation is often limited by laser-induced damage of the remaining material. A preliminary evaluation was performed of sub-100-fs, 800 nm pulsed laser ablation for depth profiling of bacterial biofilms grown on glass by the drip flow method. Electron and optical microscopy were combined with laser desorption vacuum ultraviolet postionization mass spectrometry to analyze biofilms before and after ablation. Ultrashort laser pulses can ablate 10–100 μm thick sections of bacterial biofilms, leaving behind a layer of lysed cells. However, mass spectra from intact and ablated biofilms doped with antibiotic are almost identical, indicating little chemical degradation by ablation. These results are consistent with prior observations from laser surgery and support the use of ultrashort pulse laser ablation for minimally disruptive depth profiling of bacterial biofilms and intact biological samples.
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87.85.jf Bio-based materials
81.15.Fg Pulsed laser ablation deposition
81.16.Mk Laser-assisted deposition
68.55.A- Nucleation and growth
42.62.Be Biological and medical applications

Effectiveness of passivation techniques on hydrogen desorption in a tritium environment

Steven Woodall, Edward Pines, and Delia Valles-Rosales

J. Vac. Sci. Technol. A 28, 652 (2010); http://dx.doi.org/10.1116/1.3453701 (6 pages)

Online Publication Date: 29 June 2010

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Tritium is a radioactive isotope of hydrogen. It is used as a fuel in fusion reactors, a booster material in nuclear weapons, and as a light source in commercial applications. When tritium is used in fusion reactors, and especially when used in the manufacture of nuclear weapons, purity is critical. For U.S. Department of Energy use, tritium is recycled by the Savannah River Site in South Carolina and is processed to a minimum purity of 99.5%. For use elsewhere in the country, it must be shipped and stored, while maintaining the highest purity possible. As an isotope of hydrogen, it exchanges easily with the most common isotope of hydrogen, protium. Stainless steel bottles are used to transport and store tritium. Protium, present in air, becomes associated in and on the surface of stainless steel during and after the manufacture of the steel. When filled, the tritium within the bottle exchanges with the protium in and on the surface of the stainless steel, slowly contaminating the pure tritium with protium. The stainless steel is therefore passivated to minimize the protium outgrowth of the bottles into the pure tritium. This research is to determine how effective different passivation techniques are in minimizing the contamination of tritium with protium. Additionally, this research will attempt to determine a relationship between surface chemistry of passivated steels and protium contamination of tritium. The conclusions of this research found that passivated bottles by two companies, which routinely provide passivated materials to the U.S. Department of Energy, provide low levels of protium outgrowth into pure tritium. A bottle passivated with a material to prevent excessive corrosion in a highly corrosive environment, and a clean and polished bottle provided outgrowth rates roughly twice those of the passivated bottles above. Beyond generally high levels of chromium, oxygen, iron, and nickel in the passivated bottles, there did not appear to be a strong correlation between surface chemistry in the surface of the bottles and protium outgrowth rates.
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81.65.Rv Passivation
68.43.Nr Desorption kinetics
back to top BioMEMS Focus Topic

Novel nanoporous carbon materials for adsorption gibberellic acid from solution

Jin Li, Jin-Tong Xia, Jun-Hua Zhang, and Tao Liang

J. Vac. Sci. Technol. A 28, 658 (2010); http://dx.doi.org/10.1116/1.3453699 (4 pages)

Online Publication Date: 29 June 2010

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Gibberellic acid (GA) is one kind of ubiquitous phytohormones that regulates various developmental processes of the plant growth. Monitoring and controlling the phytohormone is very important to ensure the efficient growth of crops to bring a high yield and quality production in agriculture or horticulture. Since the content of phytohormone in a plant is very low, and easily decomposed by heat, light, and oxygen, it is of considerable interest to the phytohormone research to prepare some specific absorbants for adsorption of phytohormone molecules from the solution. Here, novel nanoporous carbon with tailored pore structure has been synthesized, by dynamic carbonization with silica gel networks as a template, which was formed in sol-gel polycondensation using tetraethoxy silane as a silica precursor and sucrose as a carbon source. The pore structures of this kind of nanoporous carbon can be tunable to a high pore volume of 1.26 cm3/g and a large specific area of 1744 m2/g, which provides an adsorption capacity about 6.8 mg/g to the GA in a solution within 9 h reaction time, and it is over three to four times higher than those to protein and starch in the same solution. This indicated that the prepared nanoporous carbon materials have potential application as a novel absorbent in the separation and purification of GA from the solution for monitoring assay.
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68.43.Mn Adsorption kinetics
81.16.-c Methods of micro- and nanofabrication and processing
81.05.Rm Porous materials; granular materials
61.43.Gt Powders, porous materials
61.46.-w Structure of nanoscale materials
81.05.U- Carbon/carbon-based materials
back to top Electronic Materials and Processing

Monoclinic textured HfO2 films on GeOxNy/Ge(100) stacks using interface reconstruction by controlled thermal processing

Karen Paz Bastos, Leonardo Miotti, Gerald Lucovsky, Kwun-Bum Chung, and Dennis Nordlund

J. Vac. Sci. Technol. A 28, 662 (2010); http://dx.doi.org/10.1116/1.3430563 (3 pages)

Online Publication Date: 29 June 2010

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The authors used x-ray absorption spectroscopy of the O K edge to investigate the nanocrystalline structure of thin HfO2 films deposited by remote plasma enhanced chemical vapor deposition on Ge(100). Postdeposition thermal process induced the interfacial reconstruction and the crystallization of the HfO2 in the monoclinic structure driven by the Ge(100) substrate. The substrate templating of the HfO2 crystallization is an evidence that the processing used here removes the undesired the interfacial layer and has the potential to yield interfaces with low density of defects.
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68.55.A- Nucleation and growth
68.55.ag Semiconductors
77.55.-g Dielectric thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.46.-w Structure of nanoscale materials
78.70.Dm X-ray absorption spectra

Imaging characterization techniques applied to Cu(In,Ga)Se2 solar cells

Steve Johnston, Thomas Unold, Ingrid Repins, Rajalakshmi Sundaramoorthy, Kim M. Jones, Bobby To, Nathan Call, and Richard Ahrenkiel

J. Vac. Sci. Technol. A 28, 665 (2010); http://dx.doi.org/10.1116/1.3358303 (6 pages) | Cited 2 times

Online Publication Date: 29 June 2010

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The authors present examples of imaging characterization on Cu(In,Ga)Se2 (CIGS) solar cell devices. These imaging techniques include photoluminescence imaging, electroluminescence imaging, illuminated lock-in thermography, and forward- and reverse-bias dark lock-in thermographies. Images were collected on CIGS devices deposited at the National Renewable Energy Laboratory with intentional spatial inhomogeneities of the material parameters. Photoluminescence imaging shows brightness variations, which correlate to the device open-circuit voltage. Photoluminescence and electroluminescence imaging on CIGS solar cells show dark spots that correspond to bright spots on images from illuminated and forward-bias lock-in thermography. These image-detected defect areas are weak diodes that conduct current under solar cell operating conditions. Shunt defects are imaged using reverse-bias lock-in thermography. The authors show how imaging can be used to detect structural defects detrimental to solar cell performance. The images provide defect locations that are analyzed in more detail by scanning electron microscopy techniques using top view and cross section imaging.
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88.40.H- Solar cells (photovoltaics)
78.55.Hx Other solid inorganic materials
78.60.Fi Electroluminescence
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
88.40.J- Types of solar cells

Evaluation of indium tin oxide films grown at room temperature by pulsed electron deposition

Harshan V. Nampoori, Veronica Rincon, Mengwei Chen, and Sushma Kotru

J. Vac. Sci. Technol. A 28, 671 (2010); http://dx.doi.org/10.1116/1.3378153 (4 pages)

Online Publication Date: 29 June 2010

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Good quality Sn-doped In2O3 films with thickness of 30 nm were deposited using a vapor deposition technique known as pulsed electron deposition. The films were deposited on (100) Si substrates, at room temperature from a ceramic target of indium tin oxide (90/10). A pulsed electron beam was used for ablation of the target. Voltage of the electron source was maintained at 18 kV with frequency of pulses at 3 Hz. Distance between source and target was maintained around 6 mm, and the substrate to target distance was ∼ 7 cm. Oxygen pressure in the chamber during growth was varied from 3.1 to 20 mTorr. To evaluate the quality of grown films, various characterization techniques were employed. The effect of oxygen chamber pressure on resistivity (ρ), carrier concentration (N), mobility (μ), and optical constants (n and k) was carried out. Optical transparency and electrical conductivity of the films were seen to improve with increasing oxygen pressure. Details about the film preparation and evaluation of properties are reported.
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68.55.A- Nucleation and growth
81.10.Bk Growth from vapor

Scaling behaviors of silicon-nitride layer for charge-trapping memory

Dong Hua Li, Jang-Gn Yun, Jung Hoon Lee, and Byung-Gook Park

J. Vac. Sci. Technol. A 28, 675 (2010); http://dx.doi.org/10.1116/1.3378150 (4 pages)

Online Publication Date: 29 June 2010

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The authors investigate the scaling behaviors of a silicon-nitride layer for use in a charge-trapping memory device according to dimension downscaling of the memory-device cells. As is known, charge storage takes place in discrete traps in the silicon-nitride layer. In this study, a 5-nm-thick charge-storage layer in the conventional oxide-nitride-oxide device is investigated and shows considerable trap-based memory characteristics, but encounters a retention problem. Therefore, they adopt a modulated tunnel barrier to replace the single tunnel oxide so as to improve the charge-retention property. As a result, experimental results show excellent memory program/erase operation behaviors and indicate further scalability of the charge-storage layer compared to the conventional oxide-nitride-oxide device.
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85.30.-z Semiconductor devices
84.30.Sk Pulse and digital circuits

Fabrication of Bi2Te3/Sb2Te3 and Bi2Te3/Bi2Te2Se multilayered thin film-based integrated cooling devices

Z. Xiao, K. Hedgemen, M. Harris, and E. DiMasi

J. Vac. Sci. Technol. A 28, 679 (2010); http://dx.doi.org/10.1116/1.3292600 (5 pages) | Cited 3 times

Online Publication Date: 29 June 2010

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In this article, the authors report on the development of solid-state integrated cooling devices using Bi2Te3/Sb2Te3 and Bi2Te3/Bi2Te2Se thermoelectric thin films fabricated using sputtering deposition. The multilayer thin films have a periodic structure consisting of alternating Bi2Te3 and Sb2Te3 layers or Bi2Te3 and Bi2Te2Se layers, where each layer is about 10 nm thick. The deposited Bi2Te3/Sb2Te3 multilayer thin film has a p-type conductivity and the deposited Bi2Te3/Bi2Te2Se multilayer thin film has an n-type conductivity. The multilayer structure of films and the interface of layers were analyzed by x-ray diffraction and reflectivity. Bi2Te3/Sb2Te3 and Bi2Te3/Bi2Te2Se multilayer thin film-based integrated cooling devices were fabricated using standard integrated circuit fabrication process. The temperature difference was measured from the fabricated cooling devices. The devices could be good candidates for the application of high-efficiency solid-state microcooling.
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85.80.Fi Thermoelectric devices
85.35.-p Nanoelectronic devices
81.15.Cd Deposition by sputtering
81.16.-c Methods of micro- and nanofabrication and processing
73.50.Lw Thermoelectric effects
73.63.-b Electronic transport in nanoscale materials and structures

Schottky metal-GaN interface KOH pretreatment for improved device performance

P. B. Shah, I. Batyrev, M. A. Derenge, U. Lee, C. Nyguen, and K. A. Jones

J. Vac. Sci. Technol. A 28, 684 (2010); http://dx.doi.org/10.1116/1.3299253 (5 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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The effect of KOH pretreatment for Au/Ni Schottky contacts to GaN is investigated using I-V and x-ray photoemission spectroscopy (XPS) analysis. The molten KOH pretreatment reduces the interface trap density from 1.0×1012 to 2×1011 cm−2 eV−1, improves the on-state performance, and increases the barrier height by 10%. XPS indicates that KOH improves the GaN Schottky diode performance by eliminating an oxide layer between the metal and the semiconductor, increasing the band bending through charge transfer, and improving the GaN stoichiometry at the surface. First principle simulations indicate that the nitrogen antisite and to a minor extent the gallium antisite are also possible constituents of this interfacial layer along with gallium and nitrogen vacancies. These antisite defects can be passivated by KOH.
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73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Kk Junction diodes
61.05.js X-ray photoelectron diffraction

Chemical-etch-assisted growth of epitaxial zinc oxide

E. J. Adles and D. E. Aspnes

J. Vac. Sci. Technol. A 28, 689 (2010); http://dx.doi.org/10.1116/1.3305814 (4 pages)

Online Publication Date: 29 June 2010

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The authors use real-time spectroscopic polarimetric observations of growth, and a chemical model derived therefrom, to develop a method of growing dense, two-dimensional zinc oxide epitaxially on sapphire by metal organic chemical vapor deposition. Particulate zinc oxide formed in the gas phase is used to advantage as the deposition source. Their real-time data provide unequivocal evidence that a seed layer is required, unwanted fractions of ZnO are deposited, but these fractions can be removed by cycling between brief periods of net deposition and etching. The transition between deposition and etching occurs with zinc precursor concentrations that only differ by 13%. These processes are understood by considering the chemistry involved.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors
81.65.Cf Surface cleaning, etching, patterning
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Dz II-VI semiconductors
back to top Electronic Materials and Processing II

Ge doped HfO2 thin films investigated by x-ray absorption spectroscopy

Leonardo Miotti, Karen P. Bastos, Gerald Lucovsky, Cláudio Radtke, and Dennis Nordlund

J. Vac. Sci. Technol. A 28, 693 (2010); http://dx.doi.org/10.1116/1.3430562 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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The stability of the tetragonal phase of Ge doped HfO2 thin films on Si(100) was investigated. Hf(Ge)O2 films with Ge atomic concentrations varying from 0% to 15% were deposited by remote plasma chemical vapor deposition. The atomic structure on the oxide after rapid thermal annealing was investigated by x-ray absorption spectroscopy of the O and Ge K edges and by Rutherford backscattering spectrometry. The authors found that Ge concentrations as low as 5 at. % effectively stabilize the tetragonal phase of 5 nm thick Hf(Ge)O2 on Si and that higher concentrations are not stable to rapid thermal annealing at temperatures above 750 °C.
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77.55.D- High-permittivity gate dielectric films
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.70.Dm X-ray absorption spectra
68.55.ag Semiconductors
61.72.U- Doping and impurity implantation
back to top Magnetic Interfaces and Nanostructures

Investigations of magnetic overlayers at the Advanced Photon Source

J. G. Tobin, S.-W. Yu, M. T. Butterfield, Takashi Komesu, and G. D. Waddill

J. Vac. Sci. Technol. A 28, 697 (2010); http://dx.doi.org/10.1116/1.3271153 (5 pages) | Cited 2 times

Online Publication Date: 29 June 2010

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Magnetic overlayers of Fe and Co have been investigated with x-ray magnetic circular dichroism in x-ray absorption spectroscopy and photoelectron spectroscopy, including spin-resolved photoelectron spectroscopy, at Beamline 4 at the Advanced Photon Source. Particular emphasis was placed upon the interrogation of the 2p levels of the Fe.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.20.Ls Magneto-optical effects
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Studies of Al2O3 barriers for use in tunnel junctions for nonlocal spin detection experiments

J. Abel, J. J. Garramone, I. L. Sitnitsky, and V. P. LaBella

J. Vac. Sci. Technol. A 28, 702 (2010); http://dx.doi.org/10.1116/1.3386589 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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Aluminum oxide films were grown on Si under ultrahigh vacuum conditions for use as tunnel barriers in spin injection studies. X-ray photoelectron spectroscopy was performed to characterize the film stoichiometry. It was observed that all the aluminum was bonded to the oxygen for the films grown in 1 nm steps. Whereas the 2 nm sample grown in one 2 nm step left a partially unoxidized aluminum film. Current-voltage measurements were performed and fitted to a tunnel model. The resistance area products fall within the range needed for spin injection and nonlocal readout.
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68.55.aj Insulators
79.60.Dp Adsorbed layers and thin films
72.25.-b Spin polarized transport
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
back to top MEMS and NEMS

Imprinting of guide structure to weave nylon fibers

Harutaka Mekaru and Masaharu Takahashi

J. Vac. Sci. Technol. A 28, 706 (2010); http://dx.doi.org/10.1116/1.3386586 (7 pages) | Cited 2 times

Online Publication Date: 29 June 2010

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The authors have proposed electrical circuits accumulated by injecting electroconductive materials into patterns imprinted on the surface of fibers and weaving the fibers like a mesh. For these circuits, a built-in guide structures, which determine the positions where the fibers are to make contact with each other and exchange pertinent information, must be fabricated on fibers. In the experiments, a concave 21-μm-deep structure to serve as weaving guide was processed on the surface of 90-μm-diameter nylon fibers by thermal imprinting with a plane mold. The guides were made with two types of cross sections: rectangular and arc shaped. The rectangular structure was fabricated by a combination of microelectromechanical systems processing and Ni-electroforming technologies, whereas the arc-shaped structure involved dicing and fine machining operations. These structures on molds were designed to imprint weaving-guide structures on fibers with arrays of poles (20 μm in diameter and 10 μm in height) at their bottom to serve as fixation points for fibers and to make electric contacts after metallization. Both types of molds were made with a two-step structure that could be transferred on fibers in one single stamping operation. In thermal imprint experiments, to speed things up, the contact time was set for 1 s only. In order to compensate for the short contact time, the heating temperature was set at 100 °C, which is 50 °C higher than the glass transition temperature of nylon. Regardless of the type of mold, weaving guides and contact supports were successfully formed on the surface of nylon fibers. Thus, the capability to process complex microstructures by thermal nanoimprinting on the surface of fine fibers was experimentally proven. Moreover, the authors report on the results of the trial run for weaving imprinted nylon fibers to form fabrics.
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81.16.Nd Micro- and nanolithography
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems
81.10.Fq Growth from melts; zone melting and refining
81.20.Wk Machining, milling

Effect of polyhedral oligomeric silsesquioxane concentration on the friction and wear of dental polymers

Bharat Bhushan, Manuel Palacio, and Scott Schricker

J. Vac. Sci. Technol. A 28, 713 (2010); http://dx.doi.org/10.1116/1.3299103 (6 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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Organic-inorganic hybrid materials, such as polyhedral oligomeric silsesquioxanes (POSS), have the potential to improve the mechanical properties of methacrylate based composites and resins used in dentistry. In this article, the authors investigated the effect of the concentration of trismethacryl isobutyl POSS on the in vitro friction and wear of a composite resin mainly composed of ethoxylated bisphenol A dimethacrylate and triethyleneglycol dimethacrylate and filled with silanated silica glass. Experiments on both de-ionized water and saliva substitute were conducted. The effect of POSS on the friction and wear of the unfilled polymer resin immersed in saliva substitute were also investigated. From pin-on-disk experiments, it was found that the addition of small amounts (0.5–3 wt %) of POSS improves the friction and wear resistance of both the resin composite and the polymer resin. Samples with a higher POSS concentration (5%) showed an opposite effect, which illustrates the limited range where the reinforcement properties of POSS can operate. This concentration dependence is attributed to phase separation at higher concentrations of POSS, which affects the structural integrity, and hence, the friction and wear properties of the resin composite and the polymer resin. Depth dependence of the coefficient of friction was observed in the composite, indicating inhomogeneity from curing. The results presented in this article can serve as a useful guide in the development of novel reinforced resin composites and polymer resins for dental applications.
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81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness
81.07.Pr Organic-inorganic hybrid nanostructures
87.85.J- Biomaterials

Cryogenic inductively coupled plasma etching for fabrication of tapered through-silicon vias

A. Kamto, R. Divan, A. V. Sumant, and S. L. Burkett

J. Vac. Sci. Technol. A 28, 719 (2010); http://dx.doi.org/10.1116/1.3281005 (7 pages) | Cited 4 times

Online Publication Date: 29 June 2010

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Vertical interconnects pose an interesting method for heterogeneous integration of electronic technologies allowing three-dimensional (3D) stacking of microelectromechanical systems devices and integrated circuit components. The vertical interconnects, referred to as through-silicon vias, begin with the formation of blind vias in silicon that are eventually exposed by mechanically lapping and polishing the wafer back side. Inductively coupled plasma (ICP) etching using SF6/O2 gas chemistry at cryogenic temperatures has been investigated as a way to form vias with a tapered sidewall. The point in creating a controlled taper is so that subsequent thin films can be deposited along the sloped sidewall that line the via with insulation, barrier, and seed films. This tapering is necessary if the via lining processes do not provide adequate conformal coverage, a common problem for conventional low temperature deposition processes. In our process for lining the via sidewall, plasma enhanced chemical vapor deposited silicon dioxide is used to insulate vias from the surrounding silicon. Both Ti and Cu are sputter deposited and provide protection from copper migration and a seed film for Cu electrodeposition, respectively. After etching and lining, the vias are filled by reverse pulse plating of Cu. Vias are 20–25 μm in diameter and etched using different masking materials. The effect of changing gas flow rates, chamber pressure, ICP power, and substrate temperature on etch rate, via profile, and sidewall morphology will be presented. These parameters are critical in the optimization of an etch process for vias of specific dimensions to be used in 3D integration.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems
85.40.Sz Deposition technology
81.65.Cf Surface cleaning, etching, patterning
85.40.Ls Metallization, contacts, interconnects; device isolation
81.15.Pq Electrodeposition, electroplating
back to top Nanometer-Scale Science and Technology

Electron microscopy characterization of hexagonal molybdenum trioxide (MoO3) nanorods

C. V. Ramana, I. B. Troitskaia, V. V. Atuchin, M. Ramos, and D. Ferrer

J. Vac. Sci. Technol. A 28, 726 (2010); http://dx.doi.org/10.1116/1.3397791 (4 pages) | Cited 4 times

Online Publication Date: 30 June 2010

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A simple low-temperature chemical method to produce metastable hexagonal phase molybdenum oxide (h-MoO3) nanorods and their excellent structural characteristics has been demonstrated. In this approach, h-MoO3 samples were prepared by precipitating molybdenum oxide from an ammonium paramolybdate solution by the adding nitric acid. The structure of h-MoO3 nanorods was examined in detail using high-resolution scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM). The SEM data reveal that the nanorod h-MoO3 crystals have the shape of straight hexagonal rods with an aspect ratio ∼ 60. The HR-TEM results confirm the hexagonal structure of the MoO3 nanocrystals. Computations of the observed TEM data along with x-ray diffraction pattern further confirm the stability of the nanostructure of h-MoO3 rods.

Fabrication of quantum dots using multicoated self-assembled monolayer

Namyong Kwon, Kyohyeok Kim, and Ilsub Chung

J. Vac. Sci. Technol. A 28, 730 (2010); http://dx.doi.org/10.1116/1.3360923 (5 pages)

Online Publication Date: 29 June 2010

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The authors have fabricated quantum dots with various nanogaps by controlling the number of self-assembled molecular coatings. First, Au electrodes with a unique shape were obtained using conventional lithography. Then, a self-assembled multilayer, composed of alternating layers of 16-mercaptoalkanoic acids [HS(CH2)15COOH, 16-MHDA] and copper (II) ions, were deposited on Au electrode patterns to form the controllable gap between adjacent Au electrodes. After reaching a nanometer-scale gap, the second Au was deposited again using e-beam evaporation. Finally, both the second Au and molecular resist were removed by lift-off, thereby resulting in quantum dots with a nanogap between gold electrodes. Ellipsometry and cyclic voltammetry were used to find the number of self-assembled molecular layers. In addition, contact angle and x-ray photoelectron spectroscopy were used to analyze chemical properties between gold and the self-assembled multilayer. Field-emission scanning-electron microscopy was used for characterization of shapes of nanogaps and quantum dots.
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81.07.Ta Quantum dots
81.16.Dn Self-assembly
82.45.Mp Thin layers, films, monolayers, membranes
82.80.Fk Electrochemical methods
79.60.Jv Interfaces; heterostructures; nanostructures

Fabrication of vertically aligned Si nanowires on Si (100) substrates utilizing metal-assisted etching

Junki Hong, Kyohyeok Kim, Namyong Kwon, Jaehyun Lee, Dongmok Whang, and Ilsub Chung

J. Vac. Sci. Technol. A 28, 735 (2010); http://dx.doi.org/10.1116/1.3336572 (6 pages) | Cited 3 times

Online Publication Date: 29 June 2010

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Vertically aligned Si nanowires were fabricated utilizing a metal-assisted chemical etching scheme using a thin anodic aluminum oxide (AAO) template formed on (100) Si substrate. The diameter and length of the obtained Si nanowires were about 55 and 340 nm, respectively, when the thickness of the AAO template was about 600 nm. The diameters and shapes of the Si nanowires were determined by the hole size and shape of the Ag mesh on the AAO template. In addition, the lengths of the vertical Si nanowires depended on both the AAO thickness and the Ag film thickness.
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81.16.-c Methods of micro- and nanofabrication and processing
81.07.Gf Nanowires
81.65.Cf Surface cleaning, etching, patterning

Orientation-dependent ion beam sputtering at normal incidence conditions in FeSiAl alloy

Barbara Šetina Batič and Monika Jenko

J. Vac. Sci. Technol. A 28, 741 (2010); http://dx.doi.org/10.1116/1.3360924 (4 pages) | Cited 4 times

Online Publication Date: 29 June 2010

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The authors have performed Ar+ broad ion beam sputtering of a polycrystalline Fe–Si–Al alloy at normal incidence at energies varying from 6 to 10 keV. Sputtering results in the formation of etch pits, which can be classified in three shapes: triangular, rectangular, and square. As each grain of individual orientation exhibits a certain type of pattern, the etch pits were correlated with the crystal orientations by electron backscattered diffraction technique.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.80.Jh Ion radiation effects
61.50.-f Structure of bulk crystals
68.49.Jk Electron scattering from surfaces

Fabrication of ZnO photonic crystals by nanosphere lithography using inductively coupled-plasma reactive ion etching with CH4/H2/Ar plasma on the ZnO/GaN heterojunction light emitting diodes

Shr-Jia Chen, Chun-Ming Chang, Jiann-Shiun Kao, Fu-Rong Chen, and Chuen-Horng Tsai

J. Vac. Sci. Technol. A 28, 745 (2010); http://dx.doi.org/10.1116/1.3357282 (5 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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This article reports fabrication of n-ZnO photonic crystal/p-GaN light emitting diode (LED) by nanosphere lithography to further booster the light efficiency. In this article, the fabrication of ZnO photonic crystals is carried out by nanosphere lithography using inductively coupled plasma reactive ion etching with CH4/H2/Ar plasma on the n-ZnO/p-GaN heterojunction LEDs. The CH4/H2/Ar mixed gas gives high etching rate of n-ZnO film, which yields a better surface morphology and results less plasma-induced damages of the n-ZnO film. Optimal ZnO lattice parameters of 200 nm and air fill factor from 0.35 to 0.65 were obtained from fitting the spectrum of n-ZnO/p-GaN LED using a MATLAB code. In this article, we will show our recent result that a ZnO photonic crystal cylinder has been fabricated using polystyrene nanosphere mask with lattice parameter of 200 nm and radius of hole around 70 nm. Surface morphology of ZnO photonic crystal was examined by scanning electron microscope.
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85.60.Jb Light-emitting devices
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
81.16.Nd Micro- and nanolithography
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.70.Qs Photonic bandgap materials

Dielectrophoresis-assisted deposition and alignment of single-walled carbon nanotubes for electronic-device fabrication

Z. Xiao, H. Sharma, M. Y. Zhu, and T. Pearson

J. Vac. Sci. Technol. A 28, 750 (2010); http://dx.doi.org/10.1116/1.3378151 (5 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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Single-walled carbon nanotubes (SWCNTs) have been considered as a promising nanostructured material for the realization of future nanoelectronic devices because of their unique electrical properties, such as the ballistic transportation of electrons or holes in SWCNTs. In this article, ultrapurified high-pressure carbon monoxide-grown SWCNTs were ultrasonically dispersed in toluene, dimethylformamide, and n-methyl pyrrolidone (NMP) for deposition and alignment. NMP was found to be the best solvent to disperse SWCNTs for the dielectrophoresis (DEP)-assisted deposition and alignment of SWCNTs among the three solvents. The alternating electric field-directed DEP method was successfully used to deposit and align SWCNTs onto four pairs of gold electrodes simultaneously. The current-voltage electrical property of the aligned SWCNTs was measured and compared for the four devices. The demonstration of simultaneous deposition and alignment of SWCNTs for several devices indicates that the DEP method could be used for the fabrication of SWCNT-based integrated devices.
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81.16.-c Methods of micro- and nanofabrication and processing
61.46.Fg Nanotubes
81.07.De Nanotubes
82.45.-h Electrochemistry and electrophoresis
back to top Plasma Science and Technology

Infinitely high etch selectivity during CH2F2/H2 dual-frequency capacitively coupled plasma etching of silicon nitride to chemical vapor-deposited a-C

J. S. Kim, B. S. Kwon, W. Heo, C. R. Jung, J. S. Park, J. W. Shon, and N.-E. Lee

J. Vac. Sci. Technol. A 28, 755 (2010); http://dx.doi.org/10.1116/1.3430551 (6 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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For fabrication of a multilevel resist (MLR) structure with silicon nitride (Si3N4) and amorphous carbon (a-C) layers, highly selective etching of the Si3N4 layer using a chemical vapor-deposited (CVD) a-C etch mask was investigated by varying the following process parameters in CH2F2/H2/Ar plasmas: etch gas flow ratio, high-frequency source power (PHF), and low-frequency source power (PLF) in a dual-frequency superimposed capacitively coupled plasma etcher. The results of etching the ArF photoresist/bottom antireflective coating/SiOx/CVD a-C/Si3N4 MLR structure showed the possibility of obtaining an infinitely high selective etch process for the Si3N4 layer using a thin CVD a-C etch mask for high aspect-ratio pattern formation. The CH2F2/H2 gas flow ratio was found to play a critical role in determining the process window for infinite Si3N4/CVD a-C etch selectivity, due to the change in the degree of polymerization on Si3N4 and CVD a-C surfaces.
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81.65.Cf Surface cleaning, etching, patterning
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.35.-x Polymers: properties; reactions; polymerization

Infinitely high selective inductively coupled plasma etching of an indium tin oxide binary mask structure for extreme ultraviolet lithography

Y. R. Park, J. H. Ahn, J. S. Kim, B. S. Kwon, N.-E. Lee, H. Y. Kang, C. K. Hwangbo, Jinho Ahn, and Hwan Seok Seo

J. Vac. Sci. Technol. A 28, 761 (2010); http://dx.doi.org/10.1116/1.3425639 (5 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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Currently, extreme ultraviolet lithography (EUVL) is being investigated for next generation lithography. Among the core EUVL technologies, mask fabrication is of considerable importance due to the use of new reflective optics with a completely different configuration than those of conventional photolithography. This study investigated the etching properties of indium tin oxide (ITO) binary mask materials for EUVL, such as ITO (absorber layer), Ru (capping/etch-stop layer), and a Mo–Si multilayer (reflective layer), by varying the Cl2/Ar gas flow ratio, dc self-bias voltage (Vdc), and etch time in inductively coupled plasmas. The ITO absorber layer needs to be etched with no loss in the Ru layer on the Mo–Si multilayer for fabrication of the EUVL ITO binary mask structure proposed here. The ITO layer could be etched with an infinitely high etch selectivity over the Ru etch-stop layer in Cl2/Ar plasma even with a very high overetch time.
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85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
52.77.-j Plasma applications
back to top Advanced Surface Engineering

Coating growth behavior during the plasma electrolytic oxidation process

R. O. Hussein, D. O. Northwood, and X. Nie

J. Vac. Sci. Technol. A 28, 766 (2010); http://dx.doi.org/10.1116/1.3429583 (8 pages) | Cited 12 times

Online Publication Date: 29 June 2010

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In this study, aluminum oxide was deposited on an Al alloy substrate to produce hard ceramic coatings using a plasma electrolytic oxidation (PEO) process working at atmospheric pressure. The process utilizes dc and unipolar pulsed dc in the frequency range 0.2–20 kHz. Optical emission spectroscopy was employed to study the species and electron temperature of the plasma. The morphology and microstructure of the coatings were investigated using scanning electron microscopy. It was found that in the first 12 min of the PEO process, the plasma electron temperature increased with the applied voltage during the experiments, the plasma electron temperature was found to be in the range 4000–9000 K, and the applied voltage to the electrodes ranged up to 550–600 V for the different current modes. The plasma temperature profile exhibits a wider peak temperature spike for the dc power mode than for the pulsed dc mode, indicating that the dc plasma discharges would provide longer sintering time. The pulsed dc mode increases the spike temperature up to 8700 K but does not necessarily enhance the coating growth. The high spike temperature generated by strong discharges likely melts the oxide and then traps gas into the melt pool, resulting in some porosity at the interface. By eliminating the high temperature spike, a denser interface layer and homogenous coating morphology are produced.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.J- Morphology of films
68.55.aj Insulators
78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors
81.65.Mq Oxidation

Microstructure and corrosion resistance of nanocrystalline TiZrN films on AISI 304 stainless steel substrate

Yu-Wei Lin, Jia-Hong Huang, and Ge-Ping Yu

J. Vac. Sci. Technol. A 28, 774 (2010); http://dx.doi.org/10.1116/1.3305963 (5 pages)

Online Publication Date: 29 June 2010

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This study investigated the microstructure and properties of nanocrystalline TiZrN films on AISI 304 stainless steel substrate. TiZrN films were prepared by reactive magnetron sputtering based on the previous optimum coating conditions (substrate temperature, system pressure, nitrogen flow, etc.) for TiN and ZrN thin films. The composition ratio of TiZrN coatings were adjusted by changing the Zr target power, while keeping the Ti target power constant. Experiments were conduced to find the optimum composition with desired properties. The ratio of TiZrN composition was analyzed by x-ray photoelectron spectroscopy and Rutherford backscattering spectrometer. In terms of phase formation, there were two types of coatings that were considered: single-phase solid solutions of TiZrN and interlacing nuclei of TiZr in the matrix of TiZrN. The thickness of all TiZrN films as measured by the secondary ion mass spectroscopy was about 500 nm, and the composition depth profiles indicated that the compositions in the TiZrN films were uniform from the film surface to the 304 stainless steel substrate. The crystal structure of the TiZrN films was determined by x-ray diffraction using a M18XHF-SRA diffractometer with Cu Kα radiation. A diffraction peak of TiZrN (002) was observed between that of TiN (002) and ZrN (002); similarly, a diffraction peak of TiZrN (111) was observed between that of TiN(111) and ZrN(111), respectively. The corrosion resistance of the TiZrN film deposited on the 304 stainless steel has been investigated by electrochemical measurement. The electrolyte, 0.5M H2SO4 containing 0.05M KSCN, was used for the potentiodynamic polarization. The potentiodynamic scan was conducted from −800 to 800 mV standard calomel electrode (SCE).
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81.65.Kn Corrosion protection
81.15.Cd Deposition by sputtering
81.16.-c Methods of micro- and nanofabrication and processing
68.55.A- Nucleation and growth
82.45.Bb Corrosion and passivation
82.45.Mp Thin layers, films, monolayers, membranes
back to top Advanced Surface Engineering I

Identification of carbon sensitization for the visible-light photocatalytic titanium oxide

Y. J. Chen, G. Y. Jhan, G. L. Cai, C. S. Lin, M. S. Wong, S.-C. Ke, H. H. Lo, C. L. Cheng, and J.-J. Shyue

J. Vac. Sci. Technol. A 28, 779 (2010); http://dx.doi.org/10.1116/1.3278514 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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The authors successfully synthesized titanium oxide (TiO2) nanopowder with visible-light photocatalytic ability by low-pressure flat-flame metal organic chemical vapor condensation method. In order to confirm that carbon doping is a viable mechanism for the visible-light absorption of the powder prepared by this method, they modify the process by total exclusion of nitrogen usage to eliminate the nitrogen doping possibility. Since nitrogen is avoided in the process, the visible-light absorption cannot be due to nitrogen doping. They also found that the nanopowder formed has a single phase of anatase. Thus the nanopowder does not have anatase/rutile interface, and the authors can eliminate the possibility of visible-light absorption by the anatase/rutile interface. The visible-light absorption should thus be resort to the carbon doping. X-ray photoelectron spectroscopy studies show the presence of several carbon related bonds except Ti–C bond. This suggests that the carbon does not incorporate into the TiO2 crystal and should locate on the surface of the nanopowder. Thus the carbon species act as a visible-light sensitizer for the TiO2 as a photocatalyst. Among all carbon bonds the C–C bond is believed to be responsible for the light absorption, since all other carbon related bonds are not chromophores. The visible-light TiO2 photocatalysis induced by carbon doping is confirmed and explained.
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82.50.Hp Processes caused by visible and UV light
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.16.-c Methods of micro- and nanofabrication and processing
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.07.Wx Nanopowders
back to top Advanced Surface Engineering II

Deposition rates of high power impulse magnetron sputtering: Physics and economics

André Anders

J. Vac. Sci. Technol. A 28, 783 (2010); http://dx.doi.org/10.1116/1.3299267 (8 pages) | Cited 19 times

Online Publication Date: 29 June 2010

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Deposition by high power impulse magnetron sputtering (HIPIMS) is considered by some as the new paradigm of advanced sputtering technology, yet this is met with skepticism by others for the reported lower deposition rates, if compared to rates of more conventional sputtering of equal average power. In this contribution, the underlying physical reasons for the rate changes are discussed, including (i) ion return to the target and self-sputtering, (ii) the less-than-linear increase in the sputtering yield with increasing ion energy, (iii) yield changes due to the shift of species responsible for sputtering, (iv) changes due to greater film density, limited sticking, and self-sputtering on the substrate, (v) noticeable power losses in the switch module, (vi) changes in the magnetic balance and particle confinement of the magnetron due to self-fields at high current, and (vii) superposition of sputtering and sublimation/evaporation for selected materials. The situation is even more complicated for reactive systems where the target surface chemistry is a function of the reactive gas partial pressure and discharge conditions. While most of these factors imply a reduction in the normalized deposition rate, increased rates have been reported for certain conditions using hot targets and less poisoned targets. Finally, some points of economics and HIPIMS benefits are considered.
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81.15.Cd Deposition by sputtering
81.65.-b Surface treatments
back to top Surface Science

Effects of deposition and annealing temperatures on the electrical and optical properties of Ag2O and Cu2O–Ag2O thin films

C. C. Tseng, J. H. Hsieh, C. H. Lin, and W. Wu

J. Vac. Sci. Technol. A 28, 791 (2010); http://dx.doi.org/10.1116/1.3425638 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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Ag2O and Ag2O–Cu2O films were deposited on glass substrates by magnetron sputtering of Ag and Cu targets at various substrate temperatures. After deposition, some of these films were annealed using a rapid thermal annealing system, with the variation of temperature. An UV-VIS-NIR photometer and a Hall measurement system were used to characterize the optical and electrical properties of these films. On annealing, Ag2O (hexagonal) phase would slowly change to Ag+Ag2O (cubic) phases when the annealing temperature is greater than 200 °C. When the annealing temperature was higher than 450 °C, the Ag2O phase would transform into a metallic Ag phase completely. Accordingly, the band gap of these films will change, along with the optical and electrical properties. In the study of Ag2O–Cu2O films, it is found that these two-phase composite films could exist obviously when deposited at room temperature. The photoinduced current of these composite films could be increased significantly, compared with that of a single Cu2O phase. This is most likely due to that a large band gap semiconductor (Cu2O) is coupled with a small band gap semiconductor (Ag2O).
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81.15.Cd Deposition by sputtering
64.70.K- Solid-solid transitions
68.55.ag Semiconductors
73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors

Disposition of the axial ligand in the physical vapor deposition of organometallic complexes

Stefan Kuck, Matthias Prostak, Markus Funk, Martin Bröring, Germar Hoffmann, and Roland Wiesendanger

J. Vac. Sci. Technol. A 28, 795 (2010); http://dx.doi.org/10.1116/1.3377140 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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Axial ligands play an important role in the stabilization, functionality, and synthesis of many planar organometallic complexes. Axial ligands are often weakly bound and can easily be activated in catalytic reactions. Thermal activation and following dissociation processes have to be considered whenever sublimation procedures are used for the preparation of well-defined molecular samples under vacuum conditions. When the disposition of the axial ligand is unresolved, this potentially hampers a correct interpretation of experimental data. Here, the authors systematically address the axial ligand (X) in the system of FeIII-TriPhenylCorroles (FeTPC)-X with X = NO, 1/2 O, Cl, and (Et2O)2 adsorbed on Cu(111) in a scanning tunneling microscopy study. The authors discuss undesired side effects due to released axial ligands which are coadsorbed on a surface. NO is identified like the most appropriate axial ligand for in situ preparation of uncoordinated FeTPC whereas the adsorption of axially coordinated FeTPC was not observed.
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68.55.am Polymers and organics
68.43.Mn Adsorption kinetics
68.43.Fg Adsorbate structure (binding sites, geometry)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
back to top Surface Science I

Photon- and electron-stimulated desorption from laboratory models of interstellar ice grains

J. D. Thrower, A. G. M. Abdulgalil, M. P. Collings, M. R. S. McCoustra, D. J. Burke, W. A. Brown, A. Dawes, P. J. Holtom, P. Kendall, N. J. Mason, F. Jamme, H. J. Fraser, and F. J. M. Rutten

J. Vac. Sci. Technol. A 28, 799 (2010); http://dx.doi.org/10.1116/1.3336466 (8 pages) | Cited 3 times

Online Publication Date: 29 June 2010

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The nonthermal desorption of water from ice films induced by photon and low energy electron irradiation has been studied under conditions mimicking those found in dense interstellar clouds. Water desorption following photon irradiation at 250 nm relies on the presence of an absorbing species within the H2O ice, in this case benzene. Desorption cross sections are obtained and used to derive first order rate coefficients for the desorption processes. Kinetic modeling has been used to compare the efficiencies of these desorption mechanisms with others known to be in operation in dense clouds.
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98.38.-j Interstellar medium (ISM) and nebulae in Milky Way
61.80.Fe Electron and positron radiation effects
68.43.Nr Desorption kinetics
back to top Surface Science II

Surface three-dimensional velocity map imaging: A new technique for the study of photodesorption dynamics

Yuanyuan Ji, Sven P. K. Koehler, Daniel J. Auerbach, and Alec M. Wodtke

J. Vac. Sci. Technol. A 28, 807 (2010); http://dx.doi.org/10.1116/1.3327929 (7 pages) | Cited 1 time

Online Publication Date: 29 June 2010

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The authors describe the application of a combination of velocity map imaging and time-of-flight (TOF) techniques to obtain three-dimensional velocity distributions for surface photodesorption. They have established a systematic alignment procedure to achieve correct and reproducible experimental conditions. It includes four steps: (1) optimization of the velocity map imaging ion optics’ voltages to achieve optimum velocity map imaging conditions; (2) alignment of the surface normal with the symmetry axis (ion flight axis) of the ion optics; (3) determination of TOF distance between the surface and the ionizing laser beam; (