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Jan 2010

Volume 28, Issue 1, pp. 1-158

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Effects of dopant ion and Mn valence state in the La1−xAxMnO3 (A = Sr,Ba) colossal magnetoresistance films

Sun Gyu Choi, Seok-Joo Wang, Hyung-Ho Park, MunPyo Hong, and Kwang-Ho Kwon

J. Vac. Sci. Technol. A 28, 1 (2010); http://dx.doi.org/10.1116/1.3256197 (5 pages) | Cited 2 times

Online Publication Date: 13 November 2009

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The structural and electrical properties of Mn-based colossal magnetoresistance (CMR) thin films with controlled tolerance factor and Mn ion valance ratio were studied using crystal structure and chemical bonding character analyses. La0.7Sr0.3MnO3, La0.7Ba0.3MnO3, and La0.82Ba0.18MnO3 thin films with different contents of divalent cations and Mn3+/Mn4+ ratios were deposited on amorphous SiO2/Si substrate by rf magnetron sputtering at a substrate temperature of 350 °C. The films showed the same crystalline structure as the pseudocubic structure. The change in the sheet resistance of films was analyzed according to strain state of the unit cell, chemical bonding character of Mn–O, and Mn3+/Mn4+ ratio controlling the Mn3+–O2−–Mn4+ conducting path. Mn L-edge x-ray absorption spectra revealed that the Mn3+/Mn4+ ratio changed according to different compositions of Sr or Ba and the Mn 2p core level x-ray photoelectron spectra showed that the Mn 2p binding energy was affected by the covalence of the Mn–O bond and Mn3+/Mn4+ ratio. In addition, O K-edge x-ray absorption spectra showed covalently mixed Mn 3d and O 2p states and matched well with the resistivity changes of CMR films. Temperature coefficient of resistance values were obtained at approximately −2.16%/K to −2.46%/K of the CMR films and were correct for infrared sensor applications.
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75.47.Gk Colossal magnetoresistance
79.60.Dp Adsorbed layers and thin films
78.70.Dm X-ray absorption spectra
81.15.Cd Deposition by sputtering
78.66.Nk Insulators
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
73.61.Ng Insulators

Study of Ni2–Mn–Ga phase formation by magnetron sputtering film deposition at low temperature onto Si substrates and LaNiO3/Pb(Ti,Zr)O3 buffer

F. Figueiras, E. Rauwel, V. S. Amaral, N. Vyshatko, A. L. Kholkin, C. Soyer, D. Remiens, V. V. Shvartsman, P. Borisov, and W. Kleemann

J. Vac. Sci. Technol. A 28, 6 (2010); http://dx.doi.org/10.1116/1.3256200 (5 pages) | Cited 15 times

Online Publication Date: 13 November 2009

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Film deposition of Ni2MnGa phaselike alloy by radio frequency (rf) magnetron sputtering was performed onto bare Si(100) substrates and LaNiO3/Pb(Ti,Zr)O3 (LNO/PZT) ferroelectric buffer layer near room temperature. The prepared samples were characterized using conventional x-ray diffraction (XRD), superconducting quantum interference device, and electron dispersive x-ray spectroscopy from scanning electron microscope observations. The optimized films deposited under high rf power and low argon pressure present good surface quality and highly textured phase crystallization. The positioning distance between the substrate and the target-holder axis has some limited effect on the film’s composition due to the specific diffusion behavior of each element in the sputtering plasma. Extended four pole high resolution XRD analysis allowed one to discriminate the intended Ni–Mn–Ga tetragonal martensitic phase induced by the (100) LNO/PZT oriented buffer. This low temperature process appears to be very promising, allowing separate control of the functional layer’s properties, while trying to achieve high electromagnetoelastic coupling.
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75.70.Ak Magnetic properties of monolayers and thin films
81.15.Cd Deposition by sputtering
81.30.Kf Martensitic transformations
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.85.+t Magnetoelectric effects, multiferroics
77.55.Nv Multiferroic/magnetoelectric films

Etching characteristics and mechanism of indium tin oxide films in an inductively coupled HBr/Ar plasma

Kwang-Ho Kwon, Alexander Efremov, Yong-Hyun Ham, Nam Ki Min, Hyun Woo Lee, Mun Pyo Hong, and Kwangsoo Kim

J. Vac. Sci. Technol. A 28, 11 (2010); http://dx.doi.org/10.1116/1.3256226 (5 pages) | Cited 2 times

Online Publication Date: 13 November 2009

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The investigations of etch characteristics and mechanisms for indium tin oxide (In2O3)0.9:(SnO2)0.1 (ITO) thin films using HBr/Ar inductively coupled plasma were carried out. The ITO etch rate was measured in the range of 0%–100% Ar in the HBr/Ar mixture at fixed gas pressure (6 mTorr), input power (700 W), and bias power (200 W). Plasma parameters and composition were examined with a combination of plasma diagnostics by double Langmuir probe and global (zero-dimensional) plasma model. It was found that the ITO etch rate follows the behavior of Br atom flux but contradicts with that for H atoms and positive ions. This suggests that the ITO etch process is not limited by the ion-surface interaction kinetics and appears in the reaction-rate-limited etch regime with the Br atoms as the main chemically active species.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.70.Ds Electric and magnetic measurements

Effects of Al doping and annealing on chemical states and band diagram of Y2O3/Si gate stacks studied by photoemission and x-ray absorption spectroscopy

Satoshi Toyoda, Jun Okabayashi, Makoto Komatsu, Masaharu Oshima, Dong-Ick Lee, Shiyu Sun, Yun Sun, Piero A. Pianetta, Dmitry Kukuruznyak, and Toyohiro Chikyow

J. Vac. Sci. Technol. A 28, 16 (2010); http://dx.doi.org/10.1116/1.3259869 (4 pages) | Cited 1 time

Online Publication Date: 13 November 2009

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The authors have investigated the effects of Al doping and annealing on the photoemission spectra and thermal stability of Y2O3/Si gate stacks by photoemission spectroscopy and x-ray absorption spectroscopy. They have found that the SiO2 components diffuse into the Y2O3 layer by annealing, resulting in the formation of Y silicate; however, the formation of metallic Y silicide is not observed. The changes in valence- and conduction-band offsets by doping Y2O3 with Al with respect to both Al concentration and annealing temperature have been systematically investigated. With an increase in the Al concentration, the band offsets and band gaps increase and the conduction-band edges change nonlinearly.
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73.20.At Surface states, band structure, electron density of states
61.72.up Other materials
78.70.Dm X-ray absorption spectra
79.60.Jv Interfaces; heterostructures; nanostructures
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

In situ x-ray diffraction study of Ni–Yb interlayer and alloy systems on Si(100)

W. Knaepen, J. Demeulemeester, J. Jordan-Sweet, A. Vantomme, C. Detavernier, R. L. Van Meirhaeghe, and C. Lavoie

J. Vac. Sci. Technol. A 28, 20 (2010); http://dx.doi.org/10.1116/1.3259875 (7 pages) | Cited 1 time

Online Publication Date: 13 November 2009

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The phase formation in the ternary Ni/Yb/Si system was studied for Ni–Yb alloy and interlayer structures on Si(100) substrates using in situ x-ray diffraction measurements. Yb was treated as an alloying element in the Ni–Si system with Yb concentrations varying between 0 and 40 at. % of the Ni concentration. Independent of the initial structure of the sample, a Ni–Si or Ni–Yb compound was detected first which suggests that Ni is the dominant diffusing species during the solid state reactions. No pure Yb silicides were identified but a ternary phase (YbNi2Si2) formed in all samples after the Si atoms became mobile. Information about the distribution of the phases throughout the thin silicide film was obtained using ex situ Rutherford backscattering analysis. Independent of the Yb concentration, the NiSi phase formed at the substrate interface. As a result, the immobile Yb atoms shifted toward the sample surface and no detectable amount of Yb atoms was left at the Ni-silicide/Si interface after annealing.
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68.35.Ct Interface structure and roughness
64.70.kd Metals and alloys
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Effect of methane addition on ultrananocrystalline diamond formation: Morphology changes and induced stress

S. C. Ramos, A. F. Azevedo, M. R. Baldan, and N. G. Ferreira

J. Vac. Sci. Technol. A 28, 27 (2010); http://dx.doi.org/10.1116/1.3259885 (6 pages) | Cited 3 times

Online Publication Date: 13 November 2009

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The morphology and structure of ultrananocrystalline diamond grown on Si substrate by chemical vapor deposition are systematically studied by varying the methane concentration in the Ar/H2/CH4 precursor mixture. The films, analyzed by field-emission-gun scanning electron microscopy (FEG-SEM), showed a nanocrystallite cluster morphology that decreased its grain size (L) as a function of the CH4 addition in the gas phase. From Raman spectra, the induced stress of nanodiamond films was analyzed by the G peak shift associated with the defect incorporation and sp2 bond enhancement. The compressive stress increased as a function of CH4 addition, which also promoted the broadening of the transpolyacetylene peak as indicative of film amorphitization. The nanodiamond crystallinity was confirmed from high-resolution x-ray diffractograms, where Scherrer’s equation was applied to (111) and (200) x-ray peaks resulting in grain- size values ranging from 8.5 to 4.0 nm as the methane concentration increased, also corroborated by FEG-SEM images.
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81.05.ug Diamond
81.07.Bc Nanocrystalline materials
81.16.-c Methods of micro- and nanofabrication and processing
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.at Other materials
61.46.Hk Nanocrystals

Microstructure and temperature coefficient of resistance of thin cermet resistor films deposited from CrSi2–Cr–SiC targets by S-gun magnetron

Valery V. Felmetsger

J. Vac. Sci. Technol. A 28, 33 (2010); http://dx.doi.org/10.1116/1.3259847 (8 pages)

Online Publication Date: 16 November 2009

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Technological solutions for producing nanoscale cermet resistor films with sheet resistances above 1000 Ω/◻ and low temperature coefficients of resistance (TCR) have been investigated. 2–40 nm thick cermet films were sputter deposited from CrSi2–Cr–SiC targets by a dual cathode dc S-gun magnetron. In addition to studying film resistance versus temperature, the nanofilm structural features and composition were analyzed using scanning electron microscopy, atomic force microscopy, high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, and electron energy loss spectroscopy. This study has revealed that all cermet resistor films deposited at ambient and elevated temperatures were amorphous. The atomic ratio of Si to Cr in these films was about 2 to 1. The film TCR displayed a significant increase when the deposited film thickness was reduced below 2.5 nm. An optimized sputter process consisting of wafer degassing, cermet film deposition at elevated temperature with rf substrate bias, and a double annealing in vacuum, consisting of in situ annealing following the film sputtering and an additional annealing following the exposure of the wafers to air, has been found to be very effective for the film thermal stabilization and for fine tuning the film TCR. Cermet films with thicknesses in the range of 2.5–4 nm deposited using this technique had sheet resistances ranging from 1800 to 1200 Ω/◻ and TCR values from −50 ppm/°C to near zero, respectively. A possible mechanism responsible for the high efficiency of annealing the cermet films in vacuum (after preliminary exposure to air), resulting in resistance stabilization and TCR reduction, is also discussed.
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81.05.Mh Cermets, ceramic and refractory composites
81.05.Bx Metals, semimetals, and alloys
73.61.At Metal and metallic alloys
81.15.Cd Deposition by sputtering
81.16.-c Methods of micro- and nanofabrication and processing
68.55.at Other materials

Flexible indium zinc oxide/Ag/indium zinc oxide multilayer electrode grown on polyethersulfone substrate by cost-efficient roll-to-roll sputtering for flexible organic photovoltaics

Yong-Seok Park and Han-Ki Kim

J. Vac. Sci. Technol. A 28, 41 (2010); http://dx.doi.org/10.1116/1.3264464 (7 pages) | Cited 6 times

Online Publication Date: 16 November 2009

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The authors describe the preparation and characteristics of flexible indium zinc oxide (IZO)-Ag-IZO multilayer electrodes grown on flexible polyethersulfone (PES) substrates using a roll-to-roll sputtering system for use in flexible organic photovoltaics. By the continuous roll-to-roll sputtering of the bottom IZO, Ag, and top IZO layers at room temperature, they were able to fabricate a high quality IZO-Ag-IZO multilayer electrode with a sheet resistance of 6.15 ε/square, optical transmittance of 87.4%, and figure of merit value of 42.03×10−3 Ω−1 on the PES substrate. In addition, the IZO-Ag-IZO multilayer electrode exhibited superior flexibility to the roll-to-roll sputter grown single ITO electrode due to the existence of a ductile Ag layer between the IZO layers and stable amorphous structure of the IZO film. Furthermore, the flexible organic solar cells (OSCs) fabricated on the roll-to-roll sputter grown IZO-Ag-IZO electrode showed higher power efficiency (3.51%) than the OSCs fabricated on the roll-to-roll sputter grown single ITO electrode (2.67%).
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81.15.Cd Deposition by sputtering
68.65.Ac Multilayers
73.40.Ns Metal-nonmetal contacts
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
88.40.hj Efficiency and performance of solar cells
88.40.jr Organic photovoltaics

Influence of annealing and Ag doping on structural and optical properties of indium tin oxide thin films

Chun-Bin Cao, Lei Xiao, Xue-Ping Song, and Zhao-Qi Sun

J. Vac. Sci. Technol. A 28, 48 (2010); http://dx.doi.org/10.1116/1.3264478 (6 pages)

Online Publication Date: 18 November 2009

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Indium tin oxide (ITO) and Ag (1.2±0.1 at. %)-ITO films with the thickness of 130 nm were deposited on glass substrates at room temperature by dc magnetron sputtering and postannealed at the temperature range of 200–400 °C. By calculating the x-ray diffraction data, the lattice constants of all samples were obtained and the results show that the annealing led to the smaller lattice constants and the Ag doping resulted in the further lattice distortion. The refractive index n and extinction coefficient k of all samples were extracted from the transmittance spectra by means of the spectroscopic ellipsometry optimization method. Ag-ITO film annealed at 400 °C has the high transmittance of 80%–90% in the visible wavelength range. Ag doping dramatically increased the extinction coefficient k of ITO films in UV wavelength range but almost without change in it in visible band. Meanwhile, by contrast with ITO films, Ag-ITO films show much higher n values than that of ITO films. Finally, the optical band gaps of all samples were determined, and it has been found that there is almost no difference of band gaps between ITO and Ag-ITO films. The reasons of the influence of annealing and Ag doping on structural and optical properties of ITO thin films are discussed.
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68.55.ag Semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.72.up Other materials
81.15.Cd Deposition by sputtering
78.40.Fy Semiconductors
78.66.Li Other semiconductors

Nanocrystalline cobalt-based films with high thermal stability from a single molecule

Lucas B. Henderson, Joseph H. Rivers, Daniel E. Bost, Richard A. Jones, and John G. Ekerdt

J. Vac. Sci. Technol. A 28, 54 (2010); http://dx.doi.org/10.1116/1.3264480 (7 pages) | Cited 2 times

Online Publication Date: 20 November 2009

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Thin nanocrystalline hcp Co-based films are grown by chemical vapor deposition on SiO2. Tetrakis(trimethylphosphine)cobalt(0), ((CH3)3P)4Co, is a single-source precursor that forms Co films that incorporate both P and C when the substrate temperature ranges from 225 to 325 °C, and feature crystallites sized <15 nm. The P within the deposited film is mostly elemental with some being phosphidic, and the C exists mostly in the carbidic form along with some being graphitic. The Co is correspondingly predominantly metallic. Upon annealing to 400 °C for 3 h, some extent of both Co2P crystallite precipitation and minimal allotropic transformation to fcc Co is observed, and the amount of carbidic C is reduced relative to graphitic C, but the nanocrystalline microstructure of the film is preserved, still primarily composed of hcp Co-based crystallites.
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68.55.at Other materials
64.70.Nd Structural transitions in nanoscale materials
68.60.Dv Thermal stability; thermal effects
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Effect of anion-to-cation supplying ratio on the surface morphology of AlN films grown on ZnO substrates at low temperature

Inho Im, Mina Jung, Jieun Koo, Hyunjae Lee, Jinsub Park, Tsutomu Minegishi, Seunghwan Park, Katsushi Fujii, Takafumi Yao, Gyungsuk Kil, Takashi Hanada, and Jiho Chang

J. Vac. Sci. Technol. A 28, 61 (2010); http://dx.doi.org/10.1116/1.3264479 (4 pages)

Online Publication Date: 23 November 2009

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The authors investigated the evolution of surface morphology of AlN films grown on ZnO substrates at low temperature (LT) (400 °C) as a function of anion/cation supplying ratio (V/III ratio). Unlike the well-known favorable growth conditions for high-temperature growth, smooth-surface LT-AlN layers were obtained under the O-polar surface, stoichiometric, and N-rich conditions. LT-AlN layers revealed smooth surface (roughness in root mean square = 0.20 nm for AlN on O-polar ZnO and 0.44 nm for AlN on Zn-polar ZnO) and quite low etch-pit density ( ∼ 2×106 cm−2 for AlN/Zn-polar ZnO).
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.66.Bi Elemental solids
61.66.Dk Alloys
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)

Highly selective etching of silicon nitride to physical-vapor-deposited a-C mask in dual-frequency capacitively coupled CH2F2/H2 plasmas

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, 65 (2010); http://dx.doi.org/10.1116/1.3268624 (4 pages) | Cited 1 time

Online Publication Date: 1 December 2009

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A multilevel resist (MLR) structure can be fabricated based on a very thin amorphous carbon (a-C) layer ( ≅ 80 nm) and Si3N4 hard-mask layer ( ≅ 300 nm). The authors investigated the selective etching of the Si3N4 layer using a physical-vapor-deposited (PVD) a-C mask in a dual-frequency superimposed capacitively coupled plasma etcher by varying the process parameters in the CH2F2/H2/Ar plasmas, viz., the etch gas flow ratio, high-frequency source power (PHF), and low-frequency source power (PLF). They found that under certain etch conditions they obtain infinitely high etch selectivities of the Si3N4 layers to the PVD a-C on both the blanket and patterned wafers. The etch gas flow ratio played a critical role in determining the process window for infinitely high Si3N4/PVD a-C etch selectivity because of the change in the degree of polymerization. The etch results of a patterned ArF photoresisit/bottom antireflective coating/SiOx/PVD a-C/Si3N4 MLR structure supported the idea of using a very thin PVD a-C layer as an etch-mask layer for the Si3N4 hard-mask pattern with a pattern width of ≅ 80 nm and high aspect ratio of ≅ 5.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning

Microstructure and chemical wet etching characteristics of AlN films deposited by ac reactive magnetron sputtering

S. M. Tanner and V. V. Felmetsger

J. Vac. Sci. Technol. A 28, 69 (2010); http://dx.doi.org/10.1116/1.3268620 (8 pages) | Cited 5 times

Online Publication Date: 3 December 2009

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The influence of the surface morphology of a molybdenum underlayer on the crystallinity and etchability of reactively sputtered c-axis oriented aluminum nitride thin films was investigated. Atomic force microscopy, scanning electron microscopy, transmission electron microscopy, high resolution x-ray diffraction, and defect selective chemical etching were used to characterize the microstructure of the Mo and AlN films. 1000 nm thick films of AlN with a full width at half maximum (FWHM) of the x-ray rocking curve ranging from 1.1° to 1.9° were deposited on 300 nm thick Mo underlayers with a FWHM of around 1.5°. The Ar pressure during the Mo deposition had a critical effect on the Mo film surface morphology, affecting the structure of the subsequently deposited AlN films and, hence, their wet etching characteristics. AlN films deposited on Mo sputtered at a relatively high pressure could not be etched completely, while AlN films deposited on low pressure Mo etched more easily. Postdeposition etching of the Mo surface in Ar rf discharge prior to deposition of the AlN film was found to influence the formation of AlN residuals that were difficult to etch. Optimal rf plasma etching conditions were found, which minimized the formation of these residuals.
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68.55.ag Semiconductors
81.15.Cd Deposition by sputtering
81.65.Cf Surface cleaning, etching, patterning
68.35.bg Semiconductors
81.05.Ea III-V semiconductors

Optical emission spectroscopy as a tool for studying, optimizing, and monitoring plasma-assisted atomic layer deposition processes

A. J. M. Mackus, S. B. S. Heil, E. Langereis, H. C. M. Knoops, M. C. M. van de Sanden, and W. M. M. Kessels

J. Vac. Sci. Technol. A 28, 77 (2010); http://dx.doi.org/10.1116/1.3256227 (11 pages) | Cited 7 times

Online Publication Date: 18 December 2009

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In this note it is demonstrated that optical emission spectroscopy (OES) is an easy-to-implement and valuable tool to study, optimize, and monitor thin film growth by plasma-assisted atomic layer deposition (ALD). The species in the plasma can be identified through the analysis of the light emitted by the plasma. OES provides therefore information on the reactant species delivered to the surface by the plasma but it also yields unique insight into the surface reaction products and, as a consequence, on the reaction mechanisms of the deposition process. Time-resolved measurements reveal information about the amount of precursor dosing and length of plasma exposure needed to saturate the self-limiting half reactions, which is useful for the optimization of the ALD process. Furthermore, time-resolved OES can also be used as an easy-to-implement process monitoring tool for plasma-assisted ALD processes on production equipment; for example, to monitor reactor wall conditions or to detect process faults in real time.
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68.55.A- Nucleation and growth
78.66.-w Optical properties of specific thin films
78.47.D- Time resolved spectroscopy (>1 psec)
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Influence of oxygen partial pressure on microstructure and discharge properties of Mg–Zr–O protective films deposited by magnetron sputtering

Jianfeng Wang, Huiyan Wu, Zhongxiao Song, Yanhuai Li, Kewei Xu, and Chunliang Liu

J. Vac. Sci. Technol. A 28, 88 (2010); http://dx.doi.org/10.1116/1.3259879 (6 pages)

Online Publication Date: 18 December 2009

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Mg–Zr–O protective films for plasma display panels were deposited on soda-lime glass substrates by magnetron sputtering. The effects of oxygen partial pressure on both the discharge properties (i.e., firing voltage Vf, minimum sustaining voltage Vs, and memory coefficient MC) and the microstructure of the Mg–Zr–O films were investigated. The results show that the deposited Mg–Zr–O films retain the NaCl-type structure as the pure MgO crystal and the doped Zr exists in the form of Zr4+ substitutional solid solution in MgO crystal lattice. The grain of the films is very fine and the mean grain size is about 7 nm. As the oxygen partial pressure increases from 0.06 to 0.12 Pa, the Zr content increases and surface roughness of the films decreases. However, when oxygen partial pressure further increases, the film shows a decrease in Zr content and an increase in surface roughness. At oxygen partial pressure of 0.12 Pa, the Mg–Zr–O film has the lowest Vf and Vs and the largest MC, exhibiting the best discharge properties. The improvement of the discharge properties is thought to be related to the energy-band structure and the surface conditions of the Mg–Zr–O films.
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68.55.-a Thin film structure and morphology
73.61.Ng Insulators
68.35.bt Other materials

Irregular Au profile on the SiO2 surface and at the SiO2/Si interface and the oxidation kinetics of thermally oxidized Au-contaminated n-Si (001) surfaces

H. Shimizu, S. Shimada, S. Nagase, S. Muta, and M. Ikeda

J. Vac. Sci. Technol. A 28, 94 (2010); http://dx.doi.org/10.1116/1.3259906 (5 pages) | Cited 3 times

Online Publication Date: 18 December 2009

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The authors have studied the Au profile near the SiO2/Si interface as a function of oxidation temperature and clarified the oxidation mechanism. Clusterlike Au granules were observed on the surface of the SiO2 film (the Au surface concentration was 1.7×1015 at./cm2) of thermally oxidized Au-contaminated Si wafers, oxidized between 823 and 1123 K. As the oxidation temperature was increased, the Au granular clusters grew competitively. The clusters were observed to be both on the surface of the SiO2 film and at the SiO2/Si interface. The Au clusters were found not to bond with other elements such as O, H, and Si. The existence of a depleted or weakly inverted layer at the Si surface indicated the formation of a Au/n-Si Schottky barrier. Regarding the oxidation kinetics between 823 and 1173 K, Au rapidly enhances the growth rate of SiO2 (for SiO2 thicknesses of less than ∼ 10 nm). This result shows that Au acts as a catalyst to promote the initial growth of SiO2 on Si (001) surfaces.
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81.65.Mq Oxidation
73.30.+y Surface double layers, Schottky barriers, and work functions
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Multilayer high reflectance coating on polyethylene terephthalate film consisting of Ag/SiO2/TiO2 layers that are not quarter-wave thickness

Katsuhiko Koike, Koichi Shimada, and Shin Fukuda

J. Vac. Sci. Technol. A 28, 99 (2010); http://dx.doi.org/10.1116/1.3269736 (9 pages)

Online Publication Date: 18 December 2009

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A multilayer high reflectance coating consisting of Ag, SiO2, and TiO2 with Rvis of 99.3% was successfully designed by simulation based on Maxwell’s equations. The authors found that providing the low refractive index SiO2 layer with non-quarter-wave thickness (0.14 of nd/λ for 550 nm light) near the Ag layer made a leading contribution to this high reflectance. They successfully made a multilayer high reflectance coating of Ag/SiO2/TiO2 on polyethylene telephthalate film with Rvis of 99.4% based on that simulation. A backlight unit with a coating of Ag/SiO2/TiO2 exhibited high luminance 1.04 times that of Ag alone. Ag atoms are mixed with Si atoms upon deposit of a SiO2 layer on Ag in an atmosphere with O2. A SiO2–P layer deposited under O2 free conditions from a SiO2 ceramic target and a TiOx layer deposited from Ti work well for protection of the Ag layer from oxidation upon deposit of SiO2.
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68.55.am Polymers and organics
78.66.Qn Polymers; organic compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

High power impulse magnetron sputtering using a rotating cylindrical magnetron

W. P. Leroy, S. Mahieu, D. Depla, and A. P. Ehiasarian

J. Vac. Sci. Technol. A 28, 108 (2010); http://dx.doi.org/10.1116/1.3271136 (4 pages) | Cited 6 times

Online Publication Date: 18 December 2009

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Both the industrially favorable deposition technique, high power impulse magnetron sputtering (HIPIMS), and the industrially popular rotating cylindrical magnetron have been successfully combined. A stable operation without arcing, leaks, or other complications for the rotatable magnetron was attained, with current densities around 11 A cm−2. For Ti and Al, a much higher degree in ionization in the plasma region was observed for the HIPIMS mode compared to the direct current mode.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
52.77.Dq Plasma-based ion implantation and deposition

In situ plasma diagnostics study of a commercial high-power hollow cathode magnetron deposition tool

Liang Meng, Ramasamy Raju, Randolph Flauta, Hyungjoo Shin, David N. Ruzic, and Douglas B. Hayden

J. Vac. Sci. Technol. A 28, 112 (2010); http://dx.doi.org/10.1116/1.3271132 (7 pages) | Cited 1 time

Online Publication Date: 23 December 2009

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Using a newly designed and built plasma diagnostic system, the plasma parameters were investigated on a commercial 200 mm high-power hollow cathode magnetron (HCM) physical vapor deposition tool using Ta target under argon plasma. A three dimensional (3D) scanning radio frequency (rf)-compensated Langmuir probe was constructed to measure the spatial distribution of the electron temperature (Te) and electron density (ne) in the substrate region of the HCM tool at various input powers (2–15 kW) and pressures (10–70 mTorr). The Te was in the range of 1–3 eV, scaling with decreasing power and decreasing pressure. Meanwhile, ne was in the range of 4×1010–1×1012 cm−3 scaling with increasing power and decreasing pressure. As metal deposits on the probe during the probe measurements, a self-cleaning plasma cup was designed and installed in the chamber to clean the tungsten probe tip. However, its effectiveness in recovering the measured plasma parameters was hindered by the metal layer deposited on the insulating probe tube which was accounted for the variation in the plasma measurements. Using a quartz crystal microbalance combined with electrostatic filters, the ionization fraction of the metal flux was measured at various input power of 2–16 kW and pressure of 5–40 mTorr. The metal ionization fraction reduced significantly with the increasing input power and decreasing gas pressure which were attributed to the corresponding variation in the ionization cross section and the residence time of the sputtered atoms in the plasma, respectively. Both the metal neutral and ion flux increased at higher power and lower pressure. The 3D measurements further showed that the ionization fraction decreased when moving up from the substrate to the cathode.
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52.70.Ds Electric and magnetic measurements
52.25.Jm Ionization of plasmas
52.77.Dq Plasma-based ion implantation and deposition

Molecular thin film chemical modifications under vacuum ultraviolet irradiation

M.-P. Nghiem, Th. Tondu, J.-F. Roussel, and D. Faye

J. Vac. Sci. Technol. A 28, 119 (2010); http://dx.doi.org/10.1116/1.3271134 (8 pages) | Cited 1 time

Online Publication Date: 23 December 2009

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Spacecraft molecular contamination can be increased under vacuum ultraviolet irradiation because of contaminant sticking induced by photochemical reactions. Tridecan-2-one was experimentally studied as model contaminant. Thin films were irradiated by a deuterium lamp in order to investigate the quantitative formation of different volatility molecules. In this article, on the basis of a parametric irradiation study the authors highlight the formation of three populations of irradiation products. More volatile species come from photolysis that is showed to be strongly temperature dependent and fitted by an Arrhenius law (27 kJ/mol). Less volatile species are initially formed and eliminated afterward when photolysis stops. Nonvolatile species are continuously formed until saturation amount. With tridecan-2-one saturation occurred when 80% of the initial deposit was removed by photolysis and 20% stuck. Complementary gas chromatography coupled mass spectrometry results interpretation lead to a mechanism corresponding to primary molecular dissociation into free radicals followed by addition of radicals forming molecules of various volatility.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
82.50.Hp Processes caused by visible and UV light
82.80.Bg Chromatography
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Synthesis, characterization, and photoactivity of InTaO4 and In0.9Ni0.1TaO4 thin films prepared by electron evaporation

V. J. Rico, F. Frutos, F. Yubero, J. P. Espinos, and A. R. Gonzáles-Elipe

J. Vac. Sci. Technol. A 28, 127 (2010); http://dx.doi.org/10.1116/1.3273597 (8 pages)

Online Publication Date: 23 December 2009

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InTaO4 and In0.9Ni0.1TaO4 thin films have been prepared by electron evaporation of successive layers of the single oxide components and posterior annealing at T>800 °C. The annealed thin films presented the monoclinic crystallographic structure typical of these mixed oxides. The electrical and optical behaviors of the films, assessed by C-V measurements, surface conductivity as a function of temperature, and UV-vis absorption spectroscopy, indicate that these oxides are wide band gap semiconductors with a variable dielectric constant depending on the annealing conditions. By reflection electron energy loss spectroscopy some electronic states have been found in the gap at an energy that is compatible with the activation energy deduced from the conductivity versus 1/T plots for these oxides. The photoactivity of these materials has been assessed by looking to the evolution of the wetting contact angle as a function of the irradiation time. All the films became superhydrophilic when irradiated with UV light, while the In0.9Ni0.1TaO4 thin films also presented a small partial decrease in wetting angle when irradiated with visible photons.
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68.55.ag Semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing
79.20.Uv Electron energy loss spectroscopy
77.22.Ch Permittivity (dielectric function)
78.40.Ha Other nonmetallic inorganics
78.66.Li Other semiconductors
73.25.+i Surface conductivity and carrier phenomena
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
73.61.Le Other inorganic semiconductors

Crystallinity and resistivity of ZnO thin films with indium implantation and postannealing

Tokiyoshi Matsuda, Mamoru Furuta, Takahiro Hiramatsu, Hiroshi Furuta, and Takashi Hirao

J. Vac. Sci. Technol. A 28, 135 (2010); http://dx.doi.org/10.1116/1.3259843 (4 pages) | Cited 1 time

Online Publication Date: 30 December 2009

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Ion implantation experiments of indium (In) into sputter-deposited undoped ZnO films were carried out to control the resistivity for n+-ZnO layers of electronic device. Improvement of ZnO crystallinity after the ion implantation was revealed by x-ray diffraction patterns including a shift of lattice parameter, enhancement of peak intensity, and a decrease in full width at half maximum in 2θ. In-implanted ZnO crystallinity was greatly improved compared to results of the Ga and Al-implanted ZnO experiments. The resistivity of 1×1016 ions/cm2 implanted ZnO film was decreased with over 11 orders of magnitude to 5.1×10−2 Ω cm with postimplantation annealing at 400 °C. The ratio of resistivity between unimplanted ZnO and In-implanted one at 1×1015 ions/cm2 was seven orders of magnitude after annealing at 300 °C. The In-implanted ZnO would be suitable for fabricating source and drain regions of ZnO thin film transistors.
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73.61.Ga II-VI semiconductors
68.55.-a Thin film structure and morphology
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing

“SensArray” voltage sensor analysis in an inductively coupled plasma

M. J. Titus, C. C. Hsu, and D. B. Graves

J. Vac. Sci. Technol. A 28, 139 (2010); http://dx.doi.org/10.1116/1.3268615 (8 pages) | Cited 2 times

Online Publication Date: 30 December 2009

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A commercially manufactured PlasmaVolt™ sensor wafer was studied in an inductively coupled plasma reactor in an effort to validate sensor measurements. A pure Ar plasma at various powers (25–420 W), for a range of pressures (10–80 mT), and bias voltages (0–250 V) was utilized. A numerical sheath simulation was simultaneously developed in order to interpret experimental results. It was found that PlasmaVolt™ sensor measurements are proportional to the rf-current through the sheath. Under conditions such that the sheath impedance is dominantly capacitive, sensor measurements follow a scaling law derived from the inhomogeneous sheath model of Lieberman and Lichtenberg, [Principles of Plasma Discharges and Materials Processing (Wiley, New York, 2005)] . Under these conditions, sensor measurements are proportional to the square root of the plasma density at the plasma-sheath interface, the one-fourth root of the electron temperature, and the one-fourth root of the rf bias voltage. When the sheath impedance becomes increasingly resistive, the sensor measurements deviate from the scaling law and tend to be directly proportional to the plasma density. The measurements and numerical sheath simulation demonstrate the scaling behavior as a function of changing sheath impedance for various plasma conditions.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.40.Kh Plasma sheaths
52.25.-b Plasma properties
52.65.-y Plasma simulation

Influences of sulfur segregation to permeability in Pd-D2 permeation system

J. S. Gao, T. Hioki, N. Takahashi, and T. Motohiro

J. Vac. Sci. Technol. A 28, 147 (2010); http://dx.doi.org/10.1116/1.3273318 (5 pages)

Online Publication Date: 30 December 2009

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The influence of segregated sulfur on palladium permeability was investigated using deuterium permeation through palladium membrane, which was pretreated by annealing in vacuum and/or in air. It has been found that the palladium membrane is almost impermeable after vacuum annealing, while it is permeable after air annealing. A combination of vacuum annealing of a Pd membrane followed by annealing in air leads to better and more stable D2 permeation because S has been depleted from the Pd bulk. In fact, cleaning S from Pd in spell out (UHV) normally proceeds via cycles of high T annealing to drive S to the surface, followed by burning off the S as SO2 by heating in an O2 environment. The results in this study well demonstrate the influence of sulfur on the deuterium-permeation rate and on the behavior of sulfur segregation from Pd bulk to the surface.
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68.35.Dv Composition, segregation; defects and impurities
81.65.Cf Surface cleaning, etching, patterning
68.43.Nr Desorption kinetics

Position of segregated Al atoms and the work function: Experimental low energy electron diffraction intensity analysis and first-principles calculation of the (√3×√3)R30° superlattice phase on the (111) surface of a Cu–9 at. %Al alloy

M. Yoshitake, I. Karas, J. Houfek, S. Madeswaran, W. Song, and V. Matolín

J. Vac. Sci. Technol. A 28, 152 (2010); http://dx.doi.org/10.1116/1.3273533 (7 pages) | Cited 2 times

Online Publication Date: 30 December 2009

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The position of segregated Al atoms in the ordered (√3×√3)R30° superlattice phase on the (111) surface of a Cu–9 at. %Al alloy was precisely determined by tensor low energy electron diffraction (LEED) analysis. Work function values of the superlattice phase, the alloy without Al segregation, and Cu (111) were measured and compared. Both the position of segregated Al atoms and the work function values were computed using first-principles calculations. The conclusion from the tensor LEED analysis that the segregated Al atoms, occupying substitutional positions in bulklike lattice sites within the top layer, were located outward by 6% with respect to the plane of the top layer Cu agreed well with the calculations. The results that the work function of the alloy surface with substitutional Al segregation was very close to that without Al segregation were obtained from both the experiments and the calculations. The effect of segregation of atoms and the position of segregants on the work function value was also discussed.
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68.35.Dv Composition, segregation; defects and impurities
68.65.Cd Superlattices
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
73.30.+y Surface double layers, Schottky barriers, and work functions
65.40.gh Work functions
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