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Double-layered passivation film structure of Al₂O₃/SiN_x for high mobility oxide thin film transistors

Sang-Hee Ko Park, Min-Ki Ryu, Himchan Oh, Chi-Sun Hwang, Jae-Hong Jeon, and Sung-Min Yoon

J. Vac. Sci. Technol. B 31, 020601 (2013); http://dx.doi.org/10.1116/1.4789423 (6 pages)

Online Publication Date: 24 January 2013

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The optimization of the passivation process for oxide thin film transistors with high carrier mobility was investigated. Hydrogen incorporation into oxide channels during the deposition of SiN_x could degrade device stability and uniformity, especially for high-mobility devices. A novel double-layered passivation film structure composed of Al₂O₃/SiN_x was proposed, in which thin and dense Al₂O₃ film prepared by atomic layer deposition was introduced underneath the SiN_x layer. In-Ga-Zn-O TFT passivated with the proposed double-layered films showed no significant negative shift in turn-on voltage, even after passivation. The field-effect mobility and subthreshold swing were typically measured as 27.7 cm² V⁻¹ s⁻¹ and 0.11 V/dec, respectively. Hydrogen doping was effectively protected by the introduction of Al₂O₃ as thin as 15 nm.

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85.30.Tv	Field effect devices
81.65.Rv	Passivation
72.20.Fr	Low-field transport and mobility; piezoresistance
68.55.A-	Nucleation and growth
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

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Graphene-capped InAs/GaAs quantum dots

Hosni Ajlani, Riadh Othmen, Meherzi Oueslati, Antonnella Cavanna, and Ali Madouri

J. Vac. Sci. Technol. B 31, 020602 (2013); http://dx.doi.org/10.1116/1.4790365 (4 pages)

Online Publication Date: 31 January 2013

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Graphene was grown by chemical vapor deposition and successfully transferred onto InAs/GaAs quantum dots (QDs) grown by molecular beam epitaxy on a (001) GaAs substrate. To our knowledge, the hybrid structure of graphene replacing the conventional GaAs layer as a cap layer has not been explored until now. In this work, the authors present the photoluminescence (PL) and Raman spectroscopy study of InAs/GaAs graphene-capped QDs. The Raman measurements show an intense 2D peak at 2704 cm⁻¹ which is the main characteristic indicating the presence of graphene. The recorded PL at temperature T = 300 K shows two sharp peaks located at 1.177 and 1.191 eV, which is attributed to radiative emission from the quantum dots. These peaks, which are generally very weak in InAs/GaAs quantum dots at this temperature, are instead very intense. The enhancement of the PL emission evidenced electron transfer from the graphene layer to the QDs.

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81.07.Ta	Quantum dots
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Hi	Molecular, atomic, ion, and chemical beam epitaxy
81.05.ue	Graphene
78.67.-n	Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
81.05.Ea	III-V semiconductors

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Surface chemistry controlled diameter-modulated semiconductor nanowire superstructures

Ildar R. Musin, Dmitriy S. Boyuk, and Michael A. Filler

J. Vac. Sci. Technol. B 31, 020603 (2013); http://dx.doi.org/10.1116/1.4792660 (5 pages)

Online Publication Date: 22 February 2013

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The authors demonstrate that semiconductor nanowire diameter can be rationally controlled as a function of axial position during vapor–liquid–solid synthesis. Such nanoscale structural tuning is achieved with a “molecular resist,” specifically tetramethyltin, that adsorbs on the nanowire sidewall and restricts radial deposition without destabilizing the growth front. The temporal modulation of tetramethyltin delivery during Ge nanowire growth yields user-programmable diameter-modulated superstructures with sub-100 nm periodicities. The authors also investigate the effect of Sn accumulation in the growth catalyst and propose a second-order kinetic rate law that accurately predicts changes to nanowire axial growth rate.

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82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces
73.21.Hb	Quantum wires
61.46.Km	Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
82.20.Pm	Rate constants, reaction cross sections, and activation energies

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Effects of postdeposition annealing on a high-k-last/gate-last integration scheme for 20 nm nMOS and pMOS

Ying-Tsung Chen, Ssu-I Fu, Chien-Ting Lin, Wen-Tai Chiang, Shoou-Jinn Chang, Mon-Sen Lin, and Jyh-Shyang Jenq

J. Vac. Sci. Technol. B 31, 020604 (2013); http://dx.doi.org/10.1116/1.4793739 (3 pages)

Online Publication Date: 1 March 2013

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The authors report the use of postdeposition annealing (PDA) to improve the performance of a high-k (HK)-last/gate-last integration scheme involving the use of a chemical oxide interfacial layer (IL). They find that the chemical oxide IL can form Hf-silicate at the HK/IL interface to provide a larger effective k value and a smaller equivalent oxide thickness. They also find that they can achieve a small gate leakage current density (J_g) and minimal flat-band voltage (V_fb) degradation by PDA in O₂ atmosphere. Furthermore, they find that J_g and V_fb can be further improved by optimizing the metal gate stack.

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85.30.-z

Semiconductor devices

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Ultraclean freestanding graphene by platinum-metal catalysis

Jean-Nicolas Longchamp, Conrad Escher, and Hans-Werner Fink

J. Vac. Sci. Technol. B 31, 020605 (2013); http://dx.doi.org/10.1116/1.4793746 (3 pages)

Online Publication Date: 1 March 2013

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While freestanding clean graphene is essential for various applications, existing technologies for removing the polymer layer after transfer of graphene to the desired substrate still leave significant contaminations behind. The authors discovered a method for preparing ultraclean freestanding graphene utilizing the catalytic properties of platinum metals. Complete catalytic removal of polymer residues requires annealing in air at a temperature between 175 and 350 °C. Low-energy electron holography investigations prove that this method results in ultraclean freestanding graphene.

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61.48.Gh	Structure of graphene
81.05.ue	Graphene
61.41.+e	Polymers, elastomers, and plastics
61.72.Cc	Kinetics of defect formation and annealing
82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces
61.05.jp	Electron holography

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Metal–semiconductor–metal photodetector on as-deposited TiO₂ thin films on sapphire substrate

Deniz Çalışkan, Bayram Bütün, Şadan Özcan, and Ekmel Özbay

J. Vac. Sci. Technol. B 31, 020606 (2013); http://dx.doi.org/10.1116/1.4794526 (3 pages)

Online Publication Date: 6 March 2013

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TiO₂ thin films are prepared on c-plane sapphire substrates by the RF magnetron sputtering method. The performance of the Pt contact metal–semiconductor–metal (MSM) photodetector fabricated on as-deposited films is studied. The dark current density and the responsivity obtained were 1.57 × 10⁻⁹ A/cm² at 5 V bias and 1.73 A/W at 50 V bias, respectively. Breakdown is not observed up to 50 V bias. Rise and fall times for the photocurrent were 7 and 3 s, respectively. Our results show that high quality MSM photodetectors can be fabricated without high temperature and complicated fabrication steps.

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85.60.Gz	Photodetectors (including infrared and CCD detectors)
68.55.A-	Nucleation and growth
68.55.ag	Semiconductors
73.40.Sx	Metal-semiconductor-metal structures
81.15.Cd	Deposition by sputtering

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Synthesis, properties, and applications of silicon nanocrystals

Lorenzo Mangolini

J. Vac. Sci. Technol. B 31, 020801 (2013); http://dx.doi.org/10.1116/1.4794789 (29 pages)

Online Publication Date: 19 March 2013

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Silicon nanocrystals have been widely investigated for several years because of their many interesting properties and their potential use in several applications. This field has grown enormously after the observation of quantum confinement in porous silicon and remains an area of great interest for different reasons. Most importantly, silicon is already widely used in the semiconductor industry, is nontoxic at least in its bulk form, is the second most earth-abundant element in the crust, and is relatively cheap to process. A large number of groups have investigated silicon in the form of nanocrystals, and the authors intend to provide a comprehensive review of their contribution to the field. The author has decided to address first the synthesis and properties of silicon nanocrystals. Several different techniques, such as nucleation in substoichiometric thin films or gas-phase nucleation and growth in silane-containing nonthermal plasmas, have been proposed for the controlled synthesis of silicon nanoparticles. The author outlines the strengths and weaknesses of each approach and identify the research groups that have advanced each particular synthesis technique. The understanding of the properties of silicon nanocrystals has evolved as new synthetic approaches were developed, and for that reason the material properties are discussed together with its production approach. The use of silicon nanocrystals for the development of novel electronic devices, light emitting devices, photovoltaic cells, and for biorelated applications will be discussed. Waste heat recovery and energy storage applications are also discussed.

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81.16.-c	Methods of micro- and nanofabrication and processing
61.43.Gt	Powders, porous materials
61.46.Df	Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.30.Am	Elemental semiconductors and insulators
78.55.Ap	Elemental semiconductors
81.05.Cy	Elemental semiconductors

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Residue-free plasma etching of polyimide coatings for small pitch vias with improved step coverage

Benjamin Mimoun, Hoa T. M. Pham, Vincent Henneken, and Ronald Dekker

J. Vac. Sci. Technol. B 31, 021201 (2013); http://dx.doi.org/10.1116/1.4788795 (6 pages)

Online Publication Date: 23 January 2013

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The authors have found that patterning polyimide coatings containing organosilane adhesion promoter using pure oxygen plasma resulted in a thin silicon-rich residue layer. They show in this paper that adding small amounts of fluorine-containing gas to the etching gas mixture is necessary in order to achieve residue-free polyimide plasma etching. They report residue-free plasma etching of polyimide coatings with both isotropic and anisotropic profiles, using either metal or oxide hard masks. These etching methods are however not sufficient for the fabrication of high density metal filled vias in 10 μm thick polyimide coatings. In order to improve the metal step coverage over the vias while keeping the pitch as small as possible, the authors have developed a two-step etching recipe combining both isotropic and anisotropic profiles, resulting in wine-glass shaped vias.

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81.65.Cf	Surface cleaning, etching, patterning
52.77.Bn	Etching and cleaning
81.05.Lg	Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

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Measurement of Schottky barrier height tuning using dielectric dipole insertion method at metal–semiconductor interfaces by photoelectron spectroscopy and electrical characterization techniques

Brian E. Coss, Prasanna Sivasubramani, Barry Brennan, Prashant Majhi, Robert M. Wallace, and Jiyoung Kim

J. Vac. Sci. Technol. B 31, 021202 (2013); http://dx.doi.org/10.1116/1.4788805 (10 pages)

Online Publication Date: 30 January 2013

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Schottky barrier height (Φ_SBH) tuning from the insertion of dipole providing materials at the TaN/Si and TaN/GaAs interface are investigated using photoelectron spectroscopy and electrical techniques. In-situ processing and characterization of these contact interfaces is utilized to gain understanding of the formation of the dipole at the AlO_x/SiO₂ interface. Changes in both the band bending and vacuum work function by the insertion of AlO_x/SiO₂ at the interface are observed on both Si and GaAs substrates and are correlated with a large reduction in the Φ_SBH on Si. Applications of this contact scheme for contact resistivity reduction, extremely shallow junctions, and Schottky barrier metal–oxide–semiconductor field effect devices are also discussed.

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73.30.+y	Surface double layers, Schottky barriers, and work functions
73.40.Ns	Metal-nonmetal contacts
79.60.Jv	Interfaces; heterostructures; nanostructures
85.30.Tv	Field effect devices
68.35.Ct	Interface structure and roughness

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Ge epitaxial films on GaAs (100), (110), and (111) substrates for applications of CMOS heterostructural integrations

Shih-Hsuan Tang, Chien-I Kuo, Hai-Dang Trinh, Edward Yi Chang, Hong-Quan Nguyen, Chi-Lang Nguyen, and Guang-Li Luo

J. Vac. Sci. Technol. B 31, 021203 (2013); http://dx.doi.org/10.1116/1.4789427 (6 pages)

Online Publication Date: 30 January 2013

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Epitaxial Ge films were grown on GaAs (100), (110), and (111) substrates by using ultra-high vacuum chemical vapor deposition and studied with various methods. The incubation times and growth rates were quite different for these three GaAs substrates because the surface arsenic coverage on GaAs and hydrogen desorption energy on Ge are different for each orientation. High-resolution x-ray diffraction measurements, direct band-gap emission of photoluminescence measurements, and cross-sectional transmission electron microscopy showed that the Ge films had high crystal quality, low defect density, and sharp Ge/GaAs interfaces. In this study, atomic force microscopy analysis found that the Ge films grow on GaAs (100) and (111) via the Frank van der Merwe mode, while the Ge film grows on GaAs (110) via the Volmer-Weber mode at the initial growth stage, which can be explained by the thermodynamic theory of capillarity. Interestingly, when the thickness of the Ge film on the GaAs (110) substrate increases to ∼220 nm, the 3D Ge islands merge and form a smooth surface (rms roughness of 0.3 nm), which is useful for devices. The authors also fabricated Ge metal-oxide-semiconductor capacitors (MOSCAPs) on GaAs (100) and (110) substrates. Both Ge/GaAs (100) and Ge/GaAs (110) MOSCAPs exhibit good capacitance–voltage responses with strong inversion behaviors, which means the grown material has reached device quality. The Ge/GaAs (110) structure especially offers optimal integration of Ge pMOSFETs on GaAs substrates because Ge (110) has a high hole mobility compared with Ge (100) and (111).

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68.55.ag	Semiconductors
81.05.Cy	Elemental semiconductors
78.66.Db	Elemental semiconductors and insulators
78.55.Ap	Elemental semiconductors
84.32.Tt	Capacitors
85.30.Tv	Field effect devices

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Device instability of postannealed TiO_x thin-film transistors under gate bias stresses

Byung Du Ahn, Kyung-Chul Ok, Jin-Seong Park, and Kwun-Bum Chung

J. Vac. Sci. Technol. B 31, 021204 (2013); http://dx.doi.org/10.1116/1.4790572 (4 pages)

Online Publication Date: 6 February 2013

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This paper investigates the negative bias instability (NBS) and positive bias instability (PBS) of titanium oxide (TiO_x) thin-film transistors (TFTs) with different annealing temperatures. Structural analyses suggested that TiO_x films annealed at 450 and 550 °C had average grain sizes of 200 and 400 nm, respectively. A TiO_x TFT annealed at 550 °C exhibited respective threshold voltage (V_th) shifts of only −1.4 and 10.2 V under NBS and PBS conditions. The origin of the instability was found to be a charge trapping mechanism caused by different grain sizes, boundaries, and changes in band edge states below the conduction band, which acted as electron and hole trap sites.

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85.30.Tv

Field effect devices

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Effects of 2 MeV Ge⁺ irradiation on AlGaN/GaN high electron mobility transistors

Erica A. Douglas, Edward Bielejec, Patrick Frenzer, Bradley R. Yates, Stephen J. Pearton, Chien-Fong Lo, Lu Liu, Tsung-Sheng Kang, and Fan Ren

J. Vac. Sci. Technol. B 31, 021205 (2013); http://dx.doi.org/10.1116/1.4792370 (4 pages)

Online Publication Date: 13 February 2013

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The dc characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) were measured before and after irradiation with 2 MeV Ge⁺ ions at doses from 5 × 10¹⁰ to 5 × 10¹² cm⁻². The drain current, gate leakage current, and transconductance decreased monotonically with dose, while the drain-source resistance increased to a much greater extent than observed previously for proton irradiation of similar devices. The data are consistent with a strong decrease in electron concentration in the HEMT channel. During off-state electrical stressing of AlGaN/GaN HEMTs, the typical critical voltage for unirradiated devices was ∼13 V. By sharp contrast, no critical voltage was detected for proton irradiated HEMTs up to 35 V, indicating that the Ge irradiation had a strong influence on the electric field distribution near the gate electrode.

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85.30.Tv

Field effect devices

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Comparison of the effects of downstream H₂- and O₂-based plasmas on the removal of photoresist, silicon, and silicon nitride

Bayu Thedjoisworo, David Cheung, and Vince Crist

J. Vac. Sci. Technol. B 31, 021206 (2013); http://dx.doi.org/10.1116/1.4792254 (9 pages)

Online Publication Date: 14 February 2013

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For the 45 nm technology node and beyond, there is a need to strip photoresist quickly while suppressing the loss of materials such as polycrystalline silicon (poly-Si) and silicon nitride (Si₃N₄). To achieve this goal, the authors characterized and compared the effects of downstream pure-H₂, H₂/N₂, and O₂/N₂ plasmas on the etch behaviors of photoresist, poly-Si, and Si₃N₄. The addition of N₂ to H₂ plasma increases the photoresist ash rate to a maximum that is reached at ∼30–40% N₂, and the ash rate drops with further addition of N₂. At 30% N₂ addition, the ash rate increases by a factor of ∼3 when compared to that obtained with pure-H₂ plasma. For O₂/N₂ plasma, the photoresist ash rate also exhibits a maximum, which is attained with 5% N₂ addition, and the ash rate drops drastically as more N₂ is added. A small addition of N₂ increases the H and O radical densities in the H₂- and O₂-based plasmas, respectively, resulting in the higher ash rates. The ash rate achieved by the O₂/N₂ chemistry is generally higher than that attained with the H₂/N₂ chemistry, and the difference becomes more significant at high temperatures. The activation energy for photoresist strip under O₂/N₂ plasma was measured to be ∼10 kcal/mol, which is higher when compared to the ∼5 kcal/mol measured for both the H₂/N₂ (30% N₂) and the pure-H₂ chemistries. At 300 °C, when compared to the O₂-based chemistry, the H₂-based chemistry was shown to remove Si₃N₄ with a much lower rate, ∼0.7 Å/min, highlighting the benefit of the latter in conserving material loss. The ability of the H₂-based chemistry to suppress material loss and its nonoxidizing property could justify the trade off for its lower ash rates when compared to those obtained using the O₂-based chemistry. For the H₂-based chemistry, a small N₂ addition to the H₂ plasma was found to not only increase the ash rate but also suppress the Si etch rate by a factor of 8 to 22, depending on the temperature. Collectively, the H₂/N₂ chemistry shows a great promise for photoresist-strip applications in the advanced nodes, and it should be run at high temperatures (e.g., T ≥ 300 °C) to maximize the ash rate while still maintaining extremely low Si and Si₃N₄ losses.

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52.77.Bn	Etching and cleaning
85.40.Hp	Lithography, masks and pattern transfer
81.65.Cf	Surface cleaning, etching, patterning
52.25.-b	Plasma properties
52.77.-j	Plasma applications

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Chamber conditioning process development for improved inductively coupled plasma reactive ion etching of GaAs/AlGaAs materials

Michael K. Connors, Jason J. Plant, Kevin G. Ray, and George W. Turner

J. Vac. Sci. Technol. B 31, 021207 (2013); http://dx.doi.org/10.1116/1.4792839 (8 pages)

Online Publication Date: 19 February 2013

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Dry-etch tool preparation, which is critical to ensuring reproducible etch conditions, is particularly important in multiple-user, multiple-process-tool settings. A reproducible dry-etch process has been developed, utilizing inductively coupled plasma reactive ion etching (ICP-RIE) of GaAs and AlGaAs materials, for the fabrication of ridge structures in slab-coupled optical waveguide semiconductor diode lasers and amplifiers. A commercial ICP-RIE system was used, configured with aluminum-oxide-coated chamber components and a SiCl₄/Cl/Ar etch gas mixture. Passivation of etch chamber component surfaces by preconditioning or “seasoning” contributed to a chemically stable etch environment as monitored by tracking the GaAs etch rate. The etched areas and sidewall profiles obtained using this process were smooth, and run-to-run etch depth control was ±2% of the desired target depth of ∼1.25 μm. Energy dispersive analysis x-ray of the etch chamber surfaces before and after chamber conditioning is reported.

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81.05.Ea	III-V semiconductors
81.65.Cf	Surface cleaning, etching, patterning
42.55.Px	Semiconductor lasers; laser diodes
42.60.By	Design of specific laser systems
81.65.Rv	Passivation
52.77.Bn	Etching and cleaning

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X-ray enhanced sputter rates in argon cluster ion sputter-depth profiling of polymers

Peter J. Cumpson, Jose F. Portoles, Naoko Sano, and Anders J. Barlow

J. Vac. Sci. Technol. B 31, 021208 (2013); http://dx.doi.org/10.1116/1.4793284 (11 pages)

Online Publication Date: 22 February 2013

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The authors have observed for the first time that x-ray exposure of certain polymers of “degrading” type can greatly enhance the sputter rate of these polymers by gas cluster ion beam (GCIB) profiling. They have observed craters of similar dimensions to the x-ray spot well within the perimeter of sputter craters, indicating that x-rays can assist GCIB sputtering very significantly. This can be a major source of the loss of depth-resolution in sputter depth profiles of polymers. The authors have measured experimentally sputter craters in 14 different polymers by white-light interferometry. The results show that x-ray exposure can introduce much more topography than might previously have been expected, through both thermal and direct x-ray degradation and cross-linking. Within the region exposed to x-rays, the response of the polymer surface depends on its chemistry, with degrading (also known as type II) polymers being susceptible to large increases in sputter rate in some cases. For example, this leads to a sputter rate increase of a factor of 3 in poly-L-lactic acid (PLLA) compared to cluster-ion sputtering in the absence of x rays under typical experimental conditions. By comparison, crosslinking (also known as type I) polymers show either the same sputter rate or a reduced sputter rate due to crosslinking. The authors model this behavior using the bond scission parameter (G_S) and crosslinking parameter (G_X) used to model radiation damage in polymers. Agreement is good, allowing us to provide guidelines to assist in planning XPS depth-profiling experiments, in particular, for polymers such as PMMA and PLLA, where any requirement for uniform sputter rate is a more stringent limit to x-ray exposure than the requirement for the XPS spectra to represent chemical states quantitatively without damage.

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79.20.Rf	Atomic, molecular, and ion beam impact and interactions with surfaces
79.60.Fr	Polymers; organic compounds
82.80.Pv	Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
07.60.Ly	Interferometers
61.41.+e	Polymers, elastomers, and plastics
61.80.Jh	Ion radiation effects
68.49.Sf	Ion scattering from surfaces (charge transfer, sputtering, SIMS)

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Bound states within the notch of the HfO₂/GeO₂/Ge stack

Zhong Wang, Jason Ralph, Naser Sedghi, Ivona Z. Mitrovic, and Steve Hall

J. Vac. Sci. Technol. B 31, 021209 (2013); http://dx.doi.org/10.1116/1.4794378 (5 pages)

Online Publication Date: 4 March 2013

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A model is presented to allow calculation of the bound states in the conduction band notch at the interface between the interfacial native GeO₂ and high-κ dielectric layer in a Ge MOSFET gate stack. The notch represents a potential charge trapping site, which can induce threshold voltage instability. The model is applied to a three-dimensional structure, and the number of electrons or average occupancy of confined electrons in the notch is calculated. The effect of device physical and electrical parameters on the number of bound states and average occupancy of states in the notch is discussed. The significance of the confined charge in the notch and its effect on the threshold voltage shift in an 8-nm node Ge MOSFET is investigated. The main conclusion is that charge storage in this notch is insignificant at the relevant technology node.

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85.30.Tv	Field effect devices
85.30.De	Semiconductor-device characterization, design, and modeling

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Etching selectivity of indium tin oxide to photoresist in high density chlorine- and ethylene-containing plasmas

Steven A. Vitale and Shaun Berry

J. Vac. Sci. Technol. B 31, 021210 (2013); http://dx.doi.org/10.1116/1.4795209 (3 pages)

Online Publication Date: 13 March 2013

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Etching of indium tin oxide (ITO) thin films in high density chlorine plasmas is studied, with the goal of increasing the etching selectivity to photoresist. The ITO etching rate increases with ethylene addition, but is not affected by BCl₃ addition. ITO exhibits a threshold energy for ion etching, whereas the photoresist etches spontaneously in chlorine plasmas. The ITO:photoresist selectivity increases with BCl₃ addition, ion bombardment energy, and C₂H₄ addition. It is proposed that the ITO etching rate is limited by desorption of InCl_x products, and that ethylene addition assists in scavenging oxygen from ITO leaving loosely bound In, which is more easily removed by physical sputtering.

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81.65.Cf	Surface cleaning, etching, patterning
68.43.Nr	Desorption kinetics
52.77.Bn	Etching and cleaning
61.80.Jh	Ion radiation effects
79.20.Rf	Atomic, molecular, and ion beam impact and interactions with surfaces

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Quantum simulation of thermionic emission from diamond films

Terence D. Musho, William F. Paxton, Jim L. Davidson, and D. Greg Walker

J. Vac. Sci. Technol. B 31, 021401 (2013); http://dx.doi.org/10.1116/1.4792522 (11 pages) | Cited 1 time

Online Publication Date: 19 February 2013

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Recent advances in wide-band gap thermionic materials have brought to question the applicability of well accepted theories for thermionic emission from metallic surfaces. The authors developed a nonequilibrium Green's function (NEGF) self-consistent model based on quantum mechanics to investigate thermionic emission from nitrogen-incorporated diamond cathodes. The model allows us to relax several assumptions typical of Richardson's equation. The NEGF method is a self-consistent Schrödinger–Poisson formalism where the transport is calculated from an effective mass description and Fermi-Dirac statistics. The predictions were validated against experimental measurements from nitrogen-incorporated diamond cathodes. The model captures key emission characteristics such as the onset temperature of emission and the emission from low or negative electron-affinity materials. The results indicate that Richardson's equation overestimates emission for many cases, especially in low electron affinity materials. In addition, the model allowed them to estimate the heat flux at the cathode using the spectral emission as opposed to the mean velocity approximation, which under-predicts the cooling potential. Finally, they developed a relation between Richardson's constant, work function, and electron affinity to aid in identifying a range of Richardson's parameters applicable to experimental characterization of materials.

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79.40.+z	Thermionic emission
82.45.Fk	Electrodes
71.15.Mb	Density functional theory, local density approximation, gradient and other corrections
71.18.+y	Fermi surface: calculations and measurements; effective mass, g factor
71.20.Nr	Semiconductor compounds

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Investigation of resist filling behavior in microimprint lithography by computational fluid dynamics simulation and defocusing digital particle image velocimetry

Jun Du, Zhengying Wei, Shize Li, and Yiping Tang

J. Vac. Sci. Technol. B 31, 021601 (2013); http://dx.doi.org/10.1116/1.4788802 (9 pages)

Online Publication Date: 17 January 2013

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Resist filling behavior is crucial to the quality of final imprinted patterns in microimprint lithography (MIL). This article investigates the velocity field of the resist in microimprint lithography through numerical simulations and visualization experiments. To achieve the microscale velocity field of resist, a numerical model based on the computational fluid dynamics was built to predict the resist filling behavior, and the surface tension and contact angle were considered in this model. Meanwhile, a 3-D defocusing digital particle image velocimetry (DDPIV) was established. The spatial coordinates of the fluorescent tracer particles were derived from their DDPIV images. Time-resolved 3-D particle field inside the resist was obtained with the spatial coordinates. Particle tracking velocimetry was utilized to derive the velocity field from the particles' spatial position in the imprinting process. The investigation of the velocity field, including the horizontal and vertical velocity history, was carried out to directly describe the filling mode of the resist and hence determining the resist filling mechanism. The results of the visualization experiments and the numerical simulations were compared to obtain an in-depth understanding of the resist flow in MIL.

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47.80.Jk	Flow visualization and imaging
68.03.Cd	Surface tension and related phenomena
02.60.Cb	Numerical simulation; solution of equations
47.11.-j	Computational methods in fluid dynamics

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Diffraction-assisted extreme ultraviolet proximity lithography for fabrication of nanophotonic arrays

Serhiy Danylyuk, Hyun-su Kim, Sascha Brose, Carsten Dittberner, Peter Loosen, Thomas Taubner, Klaus Bergmann, and Larissa Juschkin

J. Vac. Sci. Technol. B 31, 021602 (2013); http://dx.doi.org/10.1116/1.4789445 (6 pages)

Online Publication Date: 25 January 2013

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In this article, the possibilities and limitations of proximity lithography with extreme ultraviolet (EUV) radiation are explored theoretically and experimentally. Utilizing partially coherent EUV radiation with a wavelength of 10.88 nm from a Xe/Ar discharge plasma EUV source, proximity patterning of various nanoantenna arrays has been performed. The experimental results are compared with the results of numerical scalar diffraction simulations, and it is shown that proximity printing in the Fresnel diffraction mode can enable production of high-resolution features even with lower resolution masks, successfully demonstrating sub-30 nm edge resolution in the resist. The potential of the method is explored by simulation of the patterning through circular and triangular apertures as well as through bowtie antenna patterns, with the results suggesting that precise control of the proximity gap and the exposure dose together with simulation-supported mask design optimizations may allow for a wide variety of high-resolution structures to be printed through relatively simple transmission masks. The method is especially suited for high-performance manufacturing of submicrometer sized nanophotonic arrays.

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42.82.Cr	Fabrication techniques; lithography, pattern transfer
42.79.-e	Optical elements, devices, and systems

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Capped carbon hard mask and trimming process: A low-cost and efficient route to nanoscale devices

Sébastien Pauliac-Vaujour, Pierre Brianceau, Corinne Comboroure, and Olivier Faynot

J. Vac. Sci. Technol. B 31, 021603 (2013); http://dx.doi.org/10.1116/1.4789349 (8 pages)

Online Publication Date: 8 February 2013

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Both sub-22 nm architecture design optimization and reliable, low-cost process development represent major challenges toward nanoscale device fabrication. In order to address the second of these two issues, the authors have demonstrated that it is possible to overcome current tool and process lithography limitations using a capped carbon hard mask process, without dramatically increasing device fabrication costs, as only existing tools are used in this process. Starting from 50 nm patterns, 25 nm fully depleted silicon-on-insulator (FDSOI) transistors with good reliability and acceptable electrical behavior are obtained. This patterning solution may be applied to existing lithography processes (dry or immersion ArF lithography) in order to enhance current resolution capabilities. Moreover, the use of a capping layer enables to set free from photoresist thickness limitations, which are becoming increasingly critical for sub-22 nm feature patterning. Indeed, for such dimensions, photoresist thickness generally needs to be lower than 66 nm in order to avoid pattern collapse effects. This trend can lead to serious integration problems especially for the fabrication of thick stack device architectures. Therefore, in addition to improving current lithography processes, our strategy may also be useful for novel lithography processes such as extreme ultraviolet lithography or maskless lithography. The authors have also demonstrated that the capped carbon hard mask process could enable the patterning of sub-11 nm FDSOI gates, with a current best result close to 7 nm, starting from 30 nm photoresist patterns. Note that all etching steps of the process have been performed in the same etching chamber, which is a key point for meeting industrial requirements. These results show that it is possible to bypass tool and process lithography limitations to pattern sub-22 nm devices without dramatically increasing fabrication costs while maintaining lithography throughput. The authors have therefore shown that the capped carbon hard mask process could be a high-performance and low-cost industry-compatible solution for nanoscale device fabrication.

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85.35.-p	Nanoelectronic devices
85.30.De	Semiconductor-device characterization, design, and modeling

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Lloyd's mirror interferometer using a single-mode fiber spatial filter

Yi-Lin Sun, David Mikolas, En-Chiang Chang, Pao-Te Lin, and Chien-Chung Fu

J. Vac. Sci. Technol. B 31, 021604 (2013); http://dx.doi.org/10.1116/1.4790660 (6 pages)

Online Publication Date: 8 February 2013

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An ultraviolet single-mode fiber is used for beam transport, spatial filtering, and beam expansion for a Lloyd's mirror interferometer for laser interference lithography. Polarized laser light at 325 nm from a HeCd laser was coupled to a nonpolarization-maintaining step-index fiber, which preserved the linear polarization with an extinction ratio exceeding 100:1. The linear polarization direction of the output beam was remotely adjusted by a half-wave plate in front of the laser. The output beam profile matched the predicted far-field distribution of the single LP01 mode step-index fiber, with a numerical aperture of 0.09 at 325 nm. By illuminating a Lloyd's mirror interferometer with the beam produced by a single fiber, line/space photoresist patterns with a pitch of 220 nm were demonstrated. Various mechanical and optical aspects that may be helpful to other research groups which are building a simple but stable interference lithography system of this technique are discussed.

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42.82.Cr	Fabrication techniques; lithography, pattern transfer
42.79.Bh	Lenses, prisms and mirrors

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Impacts of point spread function accuracy on patterning prediction and proximity effect correction in low-voltage electron-beam–direct-write lithography

Chun-Hung Liu, Philip C. W. Ng, Yu-Tian Shen, Sheng-Wei Chien, and Kuen-Yu Tsai

J. Vac. Sci. Technol. B 31, 021605 (2013); http://dx.doi.org/10.1116/1.4790655 (18 pages)

Online Publication Date: 13 February 2013

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Electron-beam–direct-write lithography at lower accelerating voltages has been considered as a candidate for next-generation lithography. Although long-range proximity effects are substantially reduced with the voltage, proximity effect correction (PEC) is still necessary since short-range proximity effects are relatively prominent. The effectiveness of model-based PEC can be limited severely if an inaccurate point spread function (PSF) characterizing electron scattering within resist is adopted. Recently, a new PSF form using a promising calibration method has been developed to more accurately characterize the electron scattering and thus significantly improve patterning fidelity at 5 keV. However, influences of adopting the conventional and new PSF forms for the usage of patterning practical circuit layouts have not been intensively studied. This work extensively investigates impacts of PSF accuracy on patterning prediction and PEC under different resist thickness conditions suitable for various lithographic half-pitch nodes, where the critical features of practical circuit layouts are used to quantitatively evaluate their performance. In addition, patterning fidelity limitation suffered from proximity effects is examined to determine whether PEC should be applied. Simulation results indicate that the new PSF form can significantly improve the fitting accuracy, patterning prediction, and PEC results over the conventional PSF forms, especially for circuit layouts with smaller feature sizes.

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85.40.Hp	Lithography, masks and pattern transfer
84.30.Bv	Circuit theory

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Improved imaging properties of thin attenuated phase shift masks for extreme ultraviolet lithography

Sangsul Lee, Inhwan Lee, Jong Gul Doh, Jae Uk Lee, Seongchul Hong, and Jinho Ahn

J. Vac. Sci. Technol. B 31, 021606 (2013); http://dx.doi.org/10.1116/1.4793298 (5 pages)

Online Publication Date: 26 February 2013

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The mask shadowing effect is a unique phenomenon caused by a mirror-based mask structure and an oblique incident angle of light in the extreme ultraviolet lithography process. This results in a horizontal–vertical (H–V) bias, an ellipticity in the contact hole pattern and, eventually, a patterning limit and critical dimension (CD) nonuniformity. Reducing the absorber thickness is the most effective method to minimize the mask shadowing effect, but this can deteriorate the mask image contrast. In this paper, an attenuated phase shift mask (PSM) is proposed as a potential method for extending the patterning limit to below 16 nm. By applying Mo as a phase shift layer, which has a refractive index (n) similar to that of the TaN absorber but with a lower absorption value, thin attenuated PSMs with various reflectivity values were obtained by controlling the Mo thickness. The proposed PSM consists of a 16.5-nm-thick TaN absorber layer and a 24-nm-thick Mo phase shifter on 2-nm-thick Ru-capped Mo/Si multilayers. This attenuated PSM results in 17.98% and 27.52% reductions in the mask error enhancement factor as well as 3.65 and 1.84 nm reductions in the H–V CD bias compared with the conventional binary intensity mask with a 70-nm-thick TaN absorber for the 22 nm line and space 1:1 vertical dense pattern under 0.25 and 0.33 numerical aperture illumination conditions, respectively. Moreover, a 10%–12% improved image contrast was obtained with 11%–17% reflectivity on the absorber stack, which corresponds to a 24–29 nm Mo thickness under 0.25 NA illumination conditions.

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81.16.Nd	Micro- and nanolithography
81.16.Rf	Micro- and nanoscale pattern formation
68.65.Ac	Multilayers
78.20.Ci	Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

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Wet etching silicon nanofins with (111)-oriented sidewalls

Lianci Liu, Vladimir V. Kuryatkov, Sergey A. Nikishin, H. Rusty Harris, and Mark Holtz

J. Vac. Sci. Technol. B 31, 021801 (2013); http://dx.doi.org/10.1116/1.4790513 (6 pages)

Online Publication Date: 5 February 2013

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A systematic study of the chemical etching of Si(111) fins is reported. Optimized wet etching of Si(110) with isopropyl alcohol and tetramethyl ammonium hydroxide produces 30 nm wide silicon nanofins with (111)-oriented sidewalls. The addition of a sacrificial silicon wafer for “doping” the etchant reduces the surface roughness of the interfin region. Atomic force microscopy indicates interfin roughness of <2 nm (root-mean square) based on scan areas of 5 μm × 5 μm. The addition of a commercial surfactant helps in reducing the presence of shoulders where the (111) and (110) crystallographic surfaces meet. Smooth sidewalls are obtained as a consequence of the directional etching process. Using electron-beam lithography and SiO₂ as a hard mask, fin aspect ratio of >8:1 with 30 nm wide fins is achieved.

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81.65.Cf	Surface cleaning, etching, patterning
81.07.Bc	Nanocrystalline materials
81.16.Nd	Micro- and nanolithography

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Effects of Cs adsorption on the field emission characteristics of closed single-walled carbon nanotubes

Po-Han Lee (李柏翰), Cheng-Ying Chiang (江政穎), Yeng-Tseng Wang (王焰增), Wen-Jay Lee (李玟頡), and Wan-Sheng Su (蘇萬生)

J. Vac. Sci. Technol. B 31, 021802 (2013); http://dx.doi.org/10.1116/1.4790510 (5 pages)

Online Publication Date: 6 February 2013

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This study employs first-principles calculations to investigate the effects of alkali-metal Cs atom adsorption on the work functions and field enhancement factors of finite-length (3,3) and (5,0) single-walled carbon nanotubes (CNTs) with capped ends. It is found that the work functions of both capped tubes decrease in the presence of an adsorbed Cs. The modified work functions are primarily due to the effect of a surface dipole at the tip of the tube. Moreover, the field enhancement factor of capped (3,3) and (5,0) tubes can be increased with this Cs adsorption, with enhancement greater in the (3,3) tube than the (5,0) tube, similar to the tendency found in pristine capped (3,3) and (5,0) tubes. Such a phenomenon can be qualitatively explained by analyzing the geometrical shape of the Cs-adsorbed nanotube system, which reveals an increase in the field enhancement factor for the Cs adsorbed system because its sharper tip causes a higher surface charge density distribution. Our findings indicate that the CNT field emission properties can be modulated more efficiently just by providing a suitable electronic source.

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68.43.Bc	Ab initio calculations of adsorbate structure and reactions
68.43.Mn	Adsorption kinetics
79.70.+q	Field emission, ionization, evaporation, and desorption
65.40.gh	Work functions

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Fabrication of multiscale electrodes on organic photovoltaic thin films and in situ electrical characterization by nanostencil combined with Qplus AFM

Benjamin Grévin, Khalil Jradi, Wan Zaireen Nisa Yahya, Rémi De Bettignies, and Renaud Demadrille

J. Vac. Sci. Technol. B 31, 021803 (2013); http://dx.doi.org/10.1116/1.4792253 (6 pages)

Online Publication Date: 12 February 2013

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The authors demonstrate the fabrication of multiscale electrodes (with lateral dimensions ranging from 10 μm to a few hundred of nanometers) on organic donor–acceptor photovoltaic thin films by mean of nanostencil lithography. The experimental setup allows the realization and in situ investigation of structures by combining nanostencil and atomic force microscopy (AFM) capabilities based on the use of tuning forks. Qplus AFM sensors with tungsten etched tips were used for near field imaging, and as microprobes to contact the deposited electrodes. The photovoltaic behavior was characterized by mean of current–voltage measurements in dark and under selective illumination. The influence of the electrode geometry on the electrical parameters is analyzed and the effect of in situ annealing is discussed in view of frequency modulation AFM images of the active layer surface morphology. This illustrates the powerfulness of nanostencil combined with Qplus AFM for local investigations of organic photovoltaic materials and in situ fabrication of devices.

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81.16.Nd	Micro- and nanolithography
81.40.Gh	Other heat and thermomechanical treatments
73.50.Pz	Photoconduction and photovoltaic effects
72.40.+w	Photoconduction and photovoltaic effects
68.35.B-	Structure of clean surfaces (and surface reconstruction)

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Preparation of porous alumina/ceria composite abrasive and its chemical mechanical polishing behavior

Sisi Chen, Hong Lei, and Ruling Chen

J. Vac. Sci. Technol. B 31, 021804 (2013); http://dx.doi.org/10.1116/1.4792373 (5 pages)

Online Publication Date: 19 February 2013

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A porous alumina/ceria composite abrasive is synthesized by the hydrothermal synthesis method with transmission electron microscope images showing that it has wormhole-like pores. The chemical mechanical polishing performance of the synthesized abrasive on hard disk substrates was then investigated and the results showed that, compared with pure porous alumina and solid alumina, the porous alumina/ceria composite abrasive has a higher material removal rate because of the presence of the active polishing element cerium. Also, the surfaces polished by the porous alumina abrasives had much fewer topographical variations and a lower surface roughness than those polished by solid alumina abrasive.

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81.05.Rm	Porous materials; granular materials
81.40.Pq	Friction, lubrication, and wear
81.65.Ps	Polishing, grinding, surface finishing
85.70.Li	Other magnetic recording and storage devices (including tapes, disks, and drums)
61.43.Gt	Powders, porous materials
62.20.Qp	Friction, tribology, and hardness

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Field emission from nanometer-scale tips of crystalline PbZr_xTi_1−xO₃

Patrick C. Fletcher, Vengadesh Kumara R. Mangalam, Lane W. Martin, and William P. King

J. Vac. Sci. Technol. B 31, 021805 (2013); http://dx.doi.org/10.1116/1.4793219 (6 pages) | Cited 1 time

Online Publication Date: 22 February 2013

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The authors report field emission from nanometer-sharp tips of polarized PbZr_xTi_1−xO₃ (PZT), silicon, and platinum. The PZT nanoemitters are fabricated in a batch fabrication process from single-crystal silicon tips that are coated with a 30 nm thick film of crystalline PZT. The nanoemitters start to emit electrons at fields as low as 2 V/μm and reach threshold emission, or turn-on, at fields as low as 3.9 V/μm. The turn-on field is 3.9 V/μm for PbZr_0.2Ti_0.8O₃, 6.8 V/μm for PbZr_0.52Ti_0.48O₃, and 10.75 V/μm for PbZr_0.8Ti_0.2O₃. The silicon nanoemitters have an electron emission turn-on field of 7.2 V/μm, and the platinum nanoemitters have an electron emission turn-on field of 5.75 V/μm. Using a Fowler-Nordheim analysis, the calculated effective work function of the PbZr_0.2Ti_0.8O₃ film is 1.00 eV, and the field amplification factor is ∼1526.

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81.07.Bc	Nanocrystalline materials
81.16.-c	Methods of micro- and nanofabrication and processing
61.46.-w	Structure of nanoscale materials
73.30.+y	Surface double layers, Schottky barriers, and work functions
79.70.+q	Field emission, ionization, evaporation, and desorption

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Controlling the silicon nanowire tapering angle in dense arrays of silicon nanowires using deep reactive ion etching

Daniel S. Engstrom and Yeong-Ah Soh

J. Vac. Sci. Technol. B 31, 021806 (2013); http://dx.doi.org/10.1116/1.4793500 (4 pages)

Online Publication Date: 27 February 2013

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The authors report on a method to control the tapering of dense arrays of sub-100 nm diameter silicon nanowires with aspect ratios larger than 30:1 using a dynamic modulation of the etch cycle time in a deep reactive ion etch process using the Bosch method. They show that when using static process parameters, dense arrays of silicon nanowires suffer from an incomplete removal of deposited passivation layer, resulting in tapered nanowires that are thicker at the base and that this effect is enhanced for dense nanowire arrays. When the gap between the nanowires is reduced from 500 to 200 nm, the tapering angle increases by up to 2°. By gradually ramping up the etch cycle time, the authors show that the nanowire tapering angle can be changed by more than 5°. The authors also show that the tapering angle sensitivity to etch cycle ramping depends on the platen power due to changes in the ion collimation.

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81.05.Cy	Elemental semiconductors
81.65.Cf	Surface cleaning, etching, patterning
81.65.Rv	Passivation
81.07.Gf	Nanowires
52.77.Bn	Etching and cleaning

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Electrical properties of platinum interconnects deposited by electron beam induced deposition of the carbon-free precursor, Pt(PF₃)₄

Colm O'Regan, Angelica Lee, Justin D. Holmes, Nikolay Petkov, Piet Trompenaars, and Hans Mulders

J. Vac. Sci. Technol. B 31, 021807 (2013); http://dx.doi.org/10.1116/1.4794343 (8 pages) | Cited 1 time

Online Publication Date: 4 March 2013

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Comprehensive analysis of the electrical properties, structure and composition of Pt interconnects, developed via mask-less, electron beam induced deposition of the carbon-free Pt precursor, Pt(PF₃)₄, is presented. The results demonstrate significantly improved electrical performance in comparison with that generated from the standard organometallic precursor, (CH₃)₃Pt(C_pCH₃). In particular, the Pt interconnects exhibited perfect ohmic behavior and resistivity that can be diminished to 0.24 × 10⁻³ Ω cm, which is only one order of magnitude higher than bulk Pt, in comparison to 0.2 Ω cm for the standard carbon-containing interconnects. A maximum current density of 1.87 × 10⁷ A cm⁻² was achieved for the carbon-free Pt, compared to 9.44 × 10⁵ A cm⁻² for the standard Pt precursor. The enhanced electrical properties of the as-deposited materials can be explained by the absence of large amounts of carbon impurities, and their further improvement by postdeposition annealing in N₂. In-situ TEM heating experiments confirmed that the annealing step induces sintering of the Pt nanocrystals and improved crystallinity, which contributes to the enhanced electrical performance. Alternative annealing under reducing conditions resulted in improved performance of the standard Pt interconnects, while the carbon-free deposit suffered electrical and structural breakage due to formation of larger Pt islands.

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72.20.-i	Conductivity phenomena in semiconductors and insulators
81.07.Bc	Nanocrystalline materials
81.20.Ev	Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
61.72.U-	Doping and impurity implantation
61.46.-w	Structure of nanoscale materials
61.72.Cc	Kinetics of defect formation and annealing

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Effect of neutral beam etching on mechanical property of microcantilevers

Yuki Nishimori, Shinji Ueki, Kazuhiro Miwa, Tomohiro Kubota, Masakazu Sugiyama, Seiji Samukawa, and Gen Hashiguchi

J. Vac. Sci. Technol. B 31, 022001 (2013); http://dx.doi.org/10.1116/1.4788829 (7 pages)

Online Publication Date: 23 January 2013

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As an effective application of neutral beam etching (NBE) to microelectromechanical systems (MEMS), here we propose a combination of conventional plasma processes and NBE to remove plasma-induced damage. To evaluate the effect of the combined approach quantitatively, we measured the resonance properties of a microcantilever before and after NBE treatment and compared them with a characteristic quantity. The thickness of the damage layer times the imaginary part of the complex Young's modulus (δE_ds), which is a parameter of surface damage. Although a plasma process makes the damaged surface of the microcantilevers during their fabrication, the removal of that damage by NBE is confirmed as a reduction in δE_ds. NBE can provide a damage-free surface for MEMS devices without a high-temperature annealing process.

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85.85.+j	Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm	Micromechanical devices and systems

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3D stepped electrodes on a flexible substrate with permanently bonded poly(dimethylsiloxane) channels for moving microfluid

Xin Guo, Kongying Xie, Robert J. Campbell, and Yongjun Lai

J. Vac. Sci. Technol. B 31, 022002 (2013); http://dx.doi.org/10.1116/1.4790651 (6 pages)

Online Publication Date: 8 February 2013

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Interdigitated microelectrode arrays have been exploited to move electrolyte via ac electro-osmosis. The performance of three dimensional (3D) stepped electrodes has been shown to exceed that of planar electrodes. However, to date all prototypes described have been based on solid silicon or glass substrates, limiting the usage of such devices. This report, to our best knowledge, is the first to describe a 3D stepped microelectrode array on a flexible Kapton^® substrate. The Kapton surface was modified to make it capable of bonding with poly(dimethylsiloxane) microchannels. The metal electrode was patterned by wet etching, a simpler process than previous approaches. Results of bonding, bending, and fluidic testing are reported. The frequency response obtained using deionized water showed maximum velocities of approximately 370 and 180 μm/s at 5V_pp for testing with a flat and bent substrate, respectively.

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85.85.+j	Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
47.60.Dx	Flows in ducts and channels
07.10.Cm	Micromechanical devices and systems
47.85.Np	Fluidics

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Dependence on proton energy of degradation of AlGaN/GaN high electron mobility transistors

Lu Liu, Chien-Fong Lo, Yuyin Xi, Yuxi Wang, Fan Ren, Stephen J. Pearton, Hong-Yeol Kim, Jihyun Kim, Robert C. Fitch, Dennis E. Walker, Jr., Kelson D. Chabak, James K. Gillespie, Stephen E. Tetlak, Glen D. Via, Antonio Crespo, et al.

J. Vac. Sci. Technol. B 31, 022201 (2013); http://dx.doi.org/10.1116/1.4788904 (7 pages)

Online Publication Date: 25 January 2013

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The effects of proton irradiation energy on dc, small signal, and large signal rf characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) were investigated. AlGaN/GaN HEMTs were irradiated with protons at fixed fluence of 5 × 10¹⁵/cm² and energies of 5, 10, and 15 MeV. Both dc and rf characteristics revealed more degradation at lower irradiation energy, with reductions of maximum transconductance of 11%, 22%, and 38%, and decreases in drain saturation current of 10%, 24%, and 46% for HEMTs exposed to 15, 10, and 5 MeV protons, respectively. The increase in device degradation with decreasing proton energy is due to the increase in linear energy transfer and corresponding increase in nonionizing energy loss with decreasing proton energy in the active region of the HEMTs. After irradiation, both subthreshold drain leakage current and reverse gate current decreased more than 1 order of magnitude for all samples. The carrier removal rate was in the range 121–336 cm⁻¹ over the range of proton energies employed in this study.

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85.30.Tv

Field effect devices

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Impact of both metal composition and oxygen/nitrogen profiles on p-channel metal-oxide semiconductor transistor threshold voltage for gate last high-k metal gate

Klaus Hempel, Robert Binder, H.-J. Engelmann, Elke Erben, Joachim Metzger, Pavel Potapov, Christopher Prindle, Dina H. Triyoso, and Andy Wei

J. Vac. Sci. Technol. B 31, 022202 (2013); http://dx.doi.org/10.1116/1.4789424 (4 pages)

Online Publication Date: 25 January 2013

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As transistor size continues to shrink, SiO₂/polySi has been replaced by high-k/metal gate (HKMG) to enable further scaling. Two different HKMG integration approaches have been implemented in high volume production: gate first and gate last—the latter is also known as replacement gate approach. In both integration schemes, getting the right threshold voltage (V_t) for NMOS and PMOS devices is critical. A number of recent studies have shown that V_t of devices is highly dependent on not just the as deposited material properties but also on subsequent processing steps. In this work, the authors developed an advanced high-resolution electron energy loss spectroscopy method capable of accurate measurement of material composition on device structures. Using this method, the nitrogen and oxygen concentration at the HKMG interface on p-channel field-effect transistor (PFET) transistors with slightly different metal gate stacks were studied. The authors demonstrated that the correct amount of nitrogen and oxygen at the HKMG interface is required to get the right PFET V_t.

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85.30.Tv

Field effect devices

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Temperature dependence of the resistive switching-related currents in ultra-thin high-k based MOSFETs

Albert Crespo-Yepes, Javier Martin-Martinez, Rosana Rodriguez, Montse Nafria, and Xavier Aymerich

J. Vac. Sci. Technol. B 31, 022203 (2013); http://dx.doi.org/10.1116/1.4789518 (5 pages)

Online Publication Date: 31 January 2013

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In this work, the temperature dependence of the resistive switching phenomenon in metal-oxide-semiconductor field-effect-transistor (MOSFETs) with an ultra-thin Hf-based high-k dielectric is studied through analysis of the gate and drain currents for the two dielectric conductivity states. These two different conductive states of the resistive switching have been associated with the dielectric breakdown (BD) and dielectric BD reversibility (R), respectively, and are related to the creation of a BD path through the dielectric that can be understood as a conductive filament. The results of the temperature dependence of the post-BD gate current are in agreement with those obtained from the study of the injected charge to recovery, which is a useful parameter with which to analyze the switch from the high to low conductivity state. The drain current in the MOSFETs for the two conductivity states, for different locations of the BD path along the channel (close to the source and close to the drain), and at several temperatures has also been studied. The results contribute to a better understanding of the resistive switching phenomenon in ultra-thin gate dielectrics. This contribution could be useful for the developing of models to describe BD reversibility.

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85.30.Tv

Field effect devices

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Band offsets of metal–oxide–semiconductor capacitor with HfLaTaO/HfSiO stacked high-k dielectric

Chin-Lung Cheng, Chi-Chung Liu, and Kuei-Shu Chang-Liao

J. Vac. Sci. Technol. B 31, 022204 (2013); http://dx.doi.org/10.1116/1.4792843 (7 pages)

Online Publication Date: 21 February 2013

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Band offsets of the metal–oxide–semiconductor (MOS) capacitor with HfLaTaO/HfSiO stacked dielectric were investigated and determined in this work. First, equivalent-oxide-thickness (EOT) of HfLaTaO/HfSiO stacked dielectric was demonstrated to be around 1.0 nm. Then, a typical flatband voltage (V_fb) versus EOT plot was used to extract the work function (Φ_m) of Ta deposited on HfLaTaO/HfSiO stacked structure. Furthermore, the Φ_m of the Ta gate electrode deposited on HfLaTaO/interfacial layer stacked dielectric was estimated to be 4.25 eV. Since the optical energy bandgap (E_gopt) is one of the most important physical parameters, the E_gopt of HfLaTaO dielectric was extracted from the HfLaTaO/quartz substrate structure by optical absorption measurements. The results suggest that the E_gopt of 5.5 eV for HfLaTaO dielectric was determined by extrapolating a linear part of the curve to the intercept on the energy axis. Moreover, the Schottky barrier height (Φ_B) was extracted from the analysis of the temperature dependence of the gate leakage current from 298 to 398 K. The result shows that the estimated Φ_B during gate injection in Ta/HfLaTaO interface is around 1.0 eV. Through the extracted values of Φ_m, E_gopt, and Φ_B, band offsets of MOS capacitor with a Ta/HfLaTaO/HfSiO/P-Si(100) stacked structure were obtained. Finally, the related degradation mechanisms of the HfLaTaO/HfSiO stacked dielectrics under constant voltage stress are presented. The interface trap density and oxide positive charges increase with increasing the injected charges and are not constant during negative bias stress.

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84.32.Tt

Capacitors

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Thermal stability of Ti, Pt, and Ru interfacial layers between seedless copper and a tantalum diffusion barrier

Xin Liu, Sean W. King, and Robert J. Nemanich

J. Vac. Sci. Technol. B 31, 022205 (2013); http://dx.doi.org/10.1116/1.4792523 (6 pages)

Online Publication Date: 26 February 2013

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The thermal stability of 7 nm Ti, Pt, and Ru interfacial adhesion layers between Cu film (10 nm) and a Ta barrier layer (4 nm) has been investigated. The barrier properties and interfacial stability have been evaluated by Rutherford backscattering spectrometry (RBS). Atomic force microscopy was used to measure the surfaces before and after annealing, and all the surfaces are relatively smooth which excludes islanding or dewetting phenomena as a cause of the instability. The RBS showed no discernible diffusion across the adhesion layer/Ta and Ta/Si interfaces which provides a stable underlying layer. For a Ti interfacial layer, RBS indicates that during 400 °C annealing, Ti interdiffuses through the Cu film and accumulates at the surface. For the Pt/Cu system, Pt interdiffusion is detected which is less evident than Ti. Among the three adhesion layer candidates, Ru shows negligible diffusion into the Cu film indicating thermal stability at 400 °C.

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68.35.Fx	Diffusion; interface formation
68.35.Np	Adhesion
68.37.Ps	Atomic force microscopy (AFM)
81.40.Gh	Other heat and thermomechanical treatments
61.05.Np	Atom, molecule, and ion scattering (for structure determination only)
66.30.Ny	Chemical interdiffusion; diffusion barriers

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Effect of electron irradiation on AlGaN/GaN and InAlN/GaN heterojunctions

Ya-Shi Hwang, Lu Liu, Fan Ren, Alexander Y. Polyakov, N. B. Smirnov, A. V. Govorkov, E. A. Kozhukhova, N. G. Kolin, V. M. Boiko, S. S. Vereyovkin, V. S. Ermakov, Chien-Fong Lo, Oleg Laboutin, Y. Cao, J. W. Johnson, et al.

J. Vac. Sci. Technol. B 31, 022206 (2013); http://dx.doi.org/10.1116/1.4795210 (6 pages)

Online Publication Date: 13 March 2013

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AlGaN/AlN/GaN/sapphire, AlGaN/GaN/sapphire, AlGaN/GaN/Si, and InAlN/GaN/sapphire heterojunctions (HJs) were irradiated with 10 MeV electrons to fluences of 2 × 10¹⁵ to 3.3 × 10¹⁶ cm⁻². The main effects on the electrical properties were a decrease in two-dimensional electron gas (2DEG) mobility and the shift of capacitance–voltage (C-V) characteristics to more positive values. The 50% 2DEG mobility decrease occurred at a similar fluence of 3.3 × 10¹⁶ cm⁻² for all AlGaN/GaN and AlGaN/AlN/GaN HJs, but at a much lower fluence of 1.3 × 10¹⁶ cm⁻² for InAlN/GaN, which is in line with previous observations for neutron irradiated HJs. The shift of C-V characteristics is due to increased concentration of deep acceptor traps in the barrier/interface region. In AlGaN/GaN/Si transistors, the increase of concentration of deep barrier/interface traps with activation energy of 0.3, 0.55, and 0.8 eV was observed. This increase correlates with the observed degradation of gate lag characteristics of transistors after irradiation with 1.3 × 10¹⁶ cm⁻² electrons.

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61.82.Fk	Semiconductors
73.40.Kp	III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Tv	Field effect devices
61.80.Fe	Electron and positron radiation effects

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Ultrahigh vacuum-compatible sockets for pin grid arrays used in nanoscale and atomic physics

Jyoti Katoch, Cameron Glasscock, and Masa Ishigami

J. Vac. Sci. Technol. B 31, 023201 (2013); http://dx.doi.org/10.1116/1.4793278 (3 pages)

Online Publication Date: 28 February 2013

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Pin grid arrays are often used for packaging devices for nanoscale and atomic physics experiments performed in ultrahigh vacuum (UHV). These arrays require their complementary socket arrays for measurements, yet UHV-compatible sockets are not commercially available. In this paper, the authors describe the design and construction of fully UHV-compatible sockets, which provide reliable electronic contact down to cryogenic temperatures and survive repeated insertion–retraction cycles.

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85.40.-e	Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
07.20.Mc	Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
84.32.Dd	Connectors, relays, and switches

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Stable field emission of single B-doped Si tips and linear current scaling of uniform tip arrays for integrated vacuum microelectronic devices

Pavel Serbun, Benjamin Bornmann, Aliaksandr Navitski, Günter Müller, Christian Prommesberger, Christoph Langer, Florian Dams, and Rupert Schreiner

J. Vac. Sci. Technol. B 31, 02B101 (2013); http://dx.doi.org/10.1116/1.4765088 (6 pages)

Online Publication Date: 7 November 2012

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Advanced Si-based semiconductor technology is most suitable to fabricate uniform nanostructures as integrated field emitter arrays for novel vacuum electronic devices. In order to improve the field emission homogeneity and stability of p-type silicon tip arrays for pulsed sensor applications, the authors have systematically studied the influence of the fabrication parameters on the tip shape and on the specific operating conditions. Based on detailed design calculations of the field enhancement, they have fabricated two series of hexagonal arrays of B-doped Si-tips in a triangular arrangement. The first (second) type contains three (four) patches with different number of tips (1, 91, 547 and 1, 19, 1027, 4447 for the first and second type, respectively) of about 1 (2.5) μm height, ∼20 (20) nm apex radius, and 20 (10) μm pitch. The field emission properties of both individual tips and complete arrays were investigated with a field emission scanning microscope at a pressure of 10⁻⁹ mbar. The current plateau of these tips typically occurs at about 10 (3) nA and around 65 (25) V/μm field level. In this carrier saturation range, single tips provide the highest current stability (<5%) and optical current switching ratio (∼2.5). Fairly homogeneous emission of the tip arrays leads to an undershooting of the expected linear scaling of the mean plateau current as well as to a much improved current stability (<1%).

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85.45.Db	Field emitters and arrays, cold electron emitters
61.46.-w	Structure of nanoscale materials
81.16.-c	Methods of micro- and nanofabrication and processing

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Illustrating field emission theory by using Lauritsen plots of transmission probability and barrier strength

Richard G. Forbes, Jonathan H. B. Deane, Andreas Fischer, and Marwan S. Mousa

J. Vac. Sci. Technol. B 31, 02B102 (2013); http://dx.doi.org/10.1116/1.4765096 (7 pages) | Cited 1 time

Online Publication Date: 7 November 2012

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This technical note relates to the theory of cold field electron emission (CFE). It starts by suggesting that, to emphasize common properties in relation to CFE theory, the term "Lauritsen plot" could be used to describe all graphical plots made with the reciprocal of barrier field (or the reciprocal of a quantity proportional to barrier field) on the horizontal axis. It then argues that Lauritsen plots related to barrier strength (G) and transmission probability (D) could play a useful role in discussion of CFE theory. Such plots would supplement conventional Fowler–Nordheim (FN) plots. All these plots would be regarded as particular types of Lauritsen plot. The Lauritsen plots of –G and lnD can be used to illustrate how basic aspects of FN tunneling theory are influenced by the mathematical form of the tunneling barrier. These, in turn, influence local emission current density and emission current. Illustrative applications used in this note relate to the well-known exact triangular and Schottky–Nordheim barriers, and to the Coulomb barrier (i.e., the electrostatic component of the electron potential energy barrier outside a model spherical emitter). For the Coulomb barrier, a good analytical series approximation has been found for the barrier-form correction factor; this can be used to predict the existence (and to some extent the properties) of related curvature in FN plots.

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79.70.+q	Field emission, ionization, evaporation, and desorption
73.40.Gk	Tunneling

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Improved approach to Fowler–Nordheim plot analysis

Richard G. Forbes, Andreas Fischer, and Marwan S. Mousa

J. Vac. Sci. Technol. B 31, 02B103 (2013); http://dx.doi.org/10.1116/1.4765080 (8 pages) | Cited 2 times

Online Publication Date: 9 November 2012

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This article introduces an improved approach to Fowler–Nordheim (FN) plot analysis, based on a new type of intercept correction factor. This factor is more cleanly defined than the factor previously used. General enabling theory is given that applies to any type of FN plot of data that can be fitted using a FN-type equation. Practical use is limited to emission situations where slope correction factors can be reliably predicted. By making a series of well-defined assumptions and approximations, it is shown how the general formulas reduce to provide an improved theory of orthodox FN-plot data analysis. This applies to situations where the circuit current is fully controlled by the emitter characteristics, and tunneling can be treated as taking place through a Schottky–Nordheim (SN) barrier. For orthodox emission, good working formulas make numerical evaluation of the slope correction factor and the new intercept correction factor quick and straightforward. A numerical illustration, using simulated emission data, shows how to use this improved approach to derive values for parameters in the full FN-type equation for the SN barrier. Good self-consistency is demonstrated. The general enabling formulas also pave the way for research aimed at developing analogous data-analysis procedures for nonorthodox emission situations.

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79.70.+q	Field emission, ionization, evaporation, and desorption
73.40.Gk	Tunneling

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Facile fabrication of scalable patterned nickel nanocone arrays for field emission applications

Ee Le Shim, Eunji Yoo, Chi Jung Kang, Young Jin Choi, Joonho Bae, Sang Bum Lee, and Kyu Wang Lee

J. Vac. Sci. Technol. B 31, 02B104 (2013); http://dx.doi.org/10.1116/1.4769349 (5 pages)

Online Publication Date: 4 December 2012

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In this report, facile fabrication of wafer-scale nickel (Ni) nanocone (NC) dot arrays as field emitters is demonstrated. Ni NC dot arrays are fabricated on silicon wafers using conventional photolithography and electrodeposition. Ni NCs with an average height of 400 nm grew in less than 3 min. Patterned Ni NC dot arrays exhibited enhanced field emission compared with plain Ni NCs. Field emission measurements of the plain NCs and patterned NC dot arrays revealed that the turn-on field of patterned NC dot arrays (3.23 V/μm) is lower than that of plain NCs (3.93 V/μm), while the field enhancement factor of patterned NC dot arrays (5087) is greater than that of plain NCs (2705). Our approach to form patterned Ni NC dot arrays is a simple, fast, cost-effective, and scalable method to fabricate effective field emitters. It is suitable for producing large-scale, patterned NC arrays for application in flat-panel displays and electron sources.

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81.05.Bx	Metals, semimetals, and alloys
81.07.-b	Nanoscale materials and structures: fabrication and characterization
81.15.Pq	Electrodeposition, electroplating
85.45.Db	Field emitters and arrays, cold electron emitters
61.46.-w	Structure of nanoscale materials
79.70.+q	Field emission, ionization, evaporation, and desorption

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Fabrication of a single-atom electron source by noble-metal surface diffusion

Tatsuhiro Nakagawa, Eiji Rokuta, Hidekazu Murata, Hiroshi Shimoyama, and Chuhei Oshima

J. Vac. Sci. Technol. B 31, 02B105 (2013); http://dx.doi.org/10.1116/1.4769966 (5 pages)

Online Publication Date: 5 December 2012

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For application as single-atom emitters, the authors have developed a new method for preparing atomic-scale pyramids with three {211}-facet sides (nanopyramids). In the new method, palladium covers the “backward” area of the tungsten tip, approximately 1 mm from the sharpened end, rather than the end itself. The palladium was deposited via surface diffusion promoted by elevating the temperature. Field ion microscopy exhibited typical signs indicating that, with the added annealing, identical nanopyramids grew spontaneously. The field emission characteristics of these nanopyramids were investigated and compared with those produced by the two established preparation methods. The authors found that field emission patterns for single-atom tips were narrow circles at low extractor voltages and three-pronged stars, indicating the presence of three ridges of the nanopyramid, at high voltages. The patterns are the same for tips prepared by whichever method. As for field emission stability, clear differences were also not seen across the preparation methods, except for a minute difference in fluctuation ratios obtained from time-dependent current data.

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85.45.Db

Field emitters and arrays, cold electron emitters

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X-ray tube with a graphite field emitter inflamed at high temperature

Yusuke Iwai, Takayoshi Koike, Youhei Hayama, Atsuo Jouzuka, Tomonori Nakamura, Yoshihiro Onizuka, Motosuke Miyoshi, and Hidenori Mimura

J. Vac. Sci. Technol. B 31, 02B106 (2013); http://dx.doi.org/10.1116/1.4769970 (4 pages)

Online Publication Date: 5 December 2012

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The authors developed a class of novel graphite-based field emitters, known as graphite field emitters inflamed at high temperature (GFEIHTs), which includes numerous edges and juts. The GFEIHT field emission characteristics are investigated in a vacuum tube (10⁻⁷ Pa), and an anode current exceeding 2 mA is obtained. The authors also fabricated tipped-off x-ray tubes using GFEIHTs. No degradation in the anode current is observed under the operating conditions of 16.6 kV anode voltage and 160 μA anode current. The current dispersion, defined as the standard deviation (σ)/mean over 24 h, is 2.8%. The authors successfully demonstrated radiography and x-ray fluorescence spectrometry using an x-ray tube with GFEIHT.

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07.85.-m	X- and γ-ray instruments
79.70.+q	Field emission, ionization, evaporation, and desorption
82.80.Ej	X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
81.05.uf	Graphite

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Observation of fringelike electron emission pattern from triode Pt nano electron source fabricated by electron-beam-induced deposition

Tomohisa Kitayama, Satoshi Abo, Fujio Wakaya, and Mikio Takai

J. Vac. Sci. Technol. B 31, 02B107 (2013); http://dx.doi.org/10.1116/1.4769976 (4 pages)

Online Publication Date: 6 December 2012

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A triode Pt nano electron source with a gate electrode to control the intensity of fringelike emission pattern with low gate voltage has been fabricated. Characteristics of the triode Pt nano electron source were measured at room temperature in a vacuum of less than 10⁻⁷ Pa. The emission current was observed when the gate voltage was higher than 30 V and showed a linear dependence in the Fowler–Nordheim plot. Electron wave interference patterns from the triode Pt nano electron source were first observed. The intensity of the electron wave interference pattern was successfully controlled by the gate voltage up to 50 V.

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79.70.+q	Field emission, ionization, evaporation, and desorption
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.16.Rf	Micro- and nanoscale pattern formation
73.23.-b	Electronic transport in mesoscopic systems

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Microplasma enhancement via the formation of a graphite-like phase on diamond cathodes

Huang-Chin Chen, I-Nan Lin, Shiu-Cheng Lou, Chulung Chen, Ray-Her Tang, Wen-Ching Shih, Shen-Chuan Lo, Li-Jen Lin, and Chi-Young Lee

J. Vac. Sci. Technol. B 31, 02B108 (2013); http://dx.doi.org/10.1116/1.4769373 (8 pages)

Online Publication Date: 10 December 2012

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Enhanced electron field emission (EFE) properties in microcrystalline diamond (MCD) films that have been Fe-coated and postannealed are observed. Additionally, improved microplasma characteristics are also observed when these materials are used as cathodes. The turn-on field for inducing the EFE process decreases from 4.7 V/μm for pristine MCD films to 2.2 V/μm for the Fe-coated/postannealed ones, whereas the EFE current density at an applied field of 8.8 V/μm increases from 36.5 to 5327.1 μA/cm². Transmission electron microscopy, in conjunction with high-angle annular dark field and 3D-tomography studies, reveals that enhanced EFE in the Fe-coated/postannealed MCD films is due to the graphite-like phase on the surface of diamond films. The authors infer that the Fe-coating interacts with the diamond in the postannealing process to dissolve carbons and reprecipitate them in nanographite networks. This process is similar to the formation of carbon nanotubes by the dissolution and reprecipitation of carbon species at the presence of nanosized Fe catalysts. The utilization of high EFE diamond films as cathode materials enhances the microplasma, as the ignition field for initiating the plasma is lowered and a high plasma current density is attainable.

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68.55.ag	Semiconductors
81.05.uf	Graphite
61.72.Cc	Kinetics of defect formation and annealing
81.07.De	Nanotubes
81.65.-b	Surface treatments
82.45.Fk	Electrodes

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Synthesis of diamond nanotips for enhancing the plasma illumination characteristics of capacitive-type plasma devices

Shiu-Cheng Lou, Chulung Chen, Kuang-Yau Teng, Chien-Yao Tang, and I-Nan Lin

J. Vac. Sci. Technol. B 31, 02B109 (2013); http://dx.doi.org/10.1116/1.4769973 (8 pages)

Online Publication Date: 10 December 2012

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The enhancement of the plasma illumination characteristics of capacitive-type plasma devices (CP-devices) utilizing diamond-coated Si-nanotips as cathodes was systematically investigated. The enhanced electron field emission (EFE) properties of the diamond films resulted in improved plasma illumination characteristics of the devices. Microcrystalline diamond films grown using ultrananocrystalline diamond as a nucleation layer (MCD/UNCD) possessed a lower turn-on field for inducing the EFE process with a higher EFE current density and resulted in a better plasma illumination performance for the CP-devices compared with those made from MCD films grown directly on Si-substrates without the nucleation layer. Transmission electron microscopy revealed that, in a two-step microwave plasma enhanced chemical vapor deposition process, the second step altered the granular structure of the UNCD nuclear layer instead of growing a layer of large-grain diamond film on top of the UNCD nucleation layer, resulting in a duplex microstructure. The MCD/UNCD films contained large diamond aggregates evenly distributed among the ultrasmall-grain matrix, with the induction of a few layers of graphite, surrounding the large aggregates. The presence of the graphene-like phase is presumed to be the prime factor resulting in the superior EFE properties of the MCD/UNCD films and the better plasma illumination characteristics of the CP-devices.

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81.05.ug	Diamond
52.25.Os	Emission, absorption, and scattering of electromagnetic radiation
52.77.Dq	Plasma-based ion implantation and deposition
81.07.Bc	Nanocrystalline materials
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

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Development of planar x-ray source using gated carbon nanotube emitter

Tomoya Manabe, Shogo Nitta, Satoshi Abo, Fujio Wakaya, and Mikio Takai

J. Vac. Sci. Technol. B 31, 02B110 (2013); http://dx.doi.org/10.1116/1.4790518 (4 pages)

Online Publication Date: 8 February 2013

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A planar x-ray source using gated carbon nanotube (CNT) emitters was developed. In the diode structure measurement, the turn-on electric field of the CNT cathode was approximately 1.2 V/μm. In the triode structure measurement, characteristic x-ray peaks of Cu and bremsstrahlung x-rays were observed. The maximum energies of the bremsstrahlung x-rays were in agreement with anode voltages. Pulse x-rays synchronized with pulsed gate voltages. Clear x-ray transmission images with high spatial resolution ≤165 μm were obtained.

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85.35.Kt	Nanotube devices
84.47.+w	Vacuum tubes

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