bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Vacancy-Like Defects in High-Rate Grown a-Si Before and After Light Soaking by Vepas
Authors: Zou X. , Chan Y. C. , Webb D. P. , Lam Y. W. , Lin S. H. , Chan F. Y. M. , Hu Y. F. , Weng X. , Beling C. D. , Fung S. 
Published: April 2011

ABSTRACTWe show how positron annihilation can distinguish vacancies in undoped hydrogenated amorphous silicon by performing Variable Energy Positron Annihilation Spectroscopy experiments before and after light soaking. We find that vacancy clusters, di-vacancies and a new type of single vacancies are created in undoped as-grown a-Si:H thin film by light illumination. The fact that the vacancy clusters are eliminated by the thermal annealing suggests that the Staebler-Wronski effect is closely related to vacancy clusters in a-Si:H material. The creation of vacancy clusters and redistribution of di-vacancies and even single vacancies probably result in photo-induced structural changes in this material.
Atomic-Scale Analysis of Plasma-Enhanced Chemical Vapor Deposition from SiH4/2 Plasmas on Si Substrates
Authors: Ramalingam Shyam , Maroudas Dimitrios , Aydil Eray S. 
Published: April 2011

ABSTRACTWe present a systematic atomic-scale analysis of the interactions of SiH3radicals originating in silane containing discharges with Si(001)-(2×1) and H-terminated Si(001)-(2×1) surfaces. Through simulations, we show that the hydrogen coverage of the surface is the key factor that controls both the surface reaction mechanism and the reaction probability. The SiH3radical reacts readily with the pristine Si(001)-(2×1) surface during the initial stages of growth while its reactivity with the corresponding H-terminated surface is considerably lower. Deposition of a-Si:H from SiH3 radicals has also been simulated by repeatedly impinging SiH3 radicals onto Si(001)-(2×1) surfaces maintained at 500 °C. During deposition under these conditions, the dominant mechanism of hydrogen removal from the surface is through abstraction by SiH3 radicals, which subsequently return to the gas phase as silane. The important reaction processes that take place during film growth have been identified and their energetics has been analyzed.
Localized or Delocalized Electrons in Microcrystalline Silicon?
Authors: Müller J. , Finger F. , Carius R. , Wagner H. 
Published: April 2011

ABSTRACTThe temperature dependence (4.2 - 300 K) of the electron spin resonance (ESR) signal at g = 1.998 and the electronic conductivity in microcrystalline silicon are measured and related with each other for a series of n-type samples. In addition the hyperfine interaction with the phosphorus donor states is investigated. The conductivity at low temperatures can be interpreted as hopping in impurity states with activation energies of a few meV very similar to n-doped crystalline silicon. The ESR intensity follows a 1/T-Curie law dependence. The carrier densities determined from the dopant concentration, electrical transport and ESR, respectively, agree surprisingly well. Little hyperfine intensity is found which is explained by exchange interaction of electrons with more than one dopant nucleus or occupation of tail states at low doping levels. It is concluded that the excess carriers introduced through doping do for their major part contribute to both transport and ESR. The results are in accordance with a position of the electrons with g=1.998 in impurity or tail states of the crystalline grains at low temperatures. With increasing temperature carriers get excited into the conduction band - a transition which is also monitored in the conductivity - where the ESR line is subject to considerable line broadening.
The Origin of the Enhanced Optical Absorption in Hot Wire Microcrystalline Silicon
Authors: Diehl F. , Schröder B. , Oechsner H. 
Published: April 2011

ABSTRACTThe phenomenon of enhanced optical absorption in hot wire microcrystalline silicon (hw-μ-Si:H) has been investigated with respect to the structural properties of the as deposited as well as annealed films. The influence of the structural properties on the absorption behavior is explained within the framework of a model. In this model the μc-Si:H is assumed to consist of crystalline grains surrounded by grain boundaries embedded into an amorphous matrix. Because of the relaxation of the k-selection rule the absorption is supposed to be higher for the disordered grain boundaries than for the crystalline grains. The absorption coefficient α is derived from the superposition of the absorption coefficients for the amorphous, crystalline and grain boundary regions weighted by their appropriate volume fractions. According to experimental results it is furthermore assumed that the absorption of the grain boundary regions correlates with the hydrogen content of the films. The model is proven and confirmed by crucial experiments especially concerning the influence of the hydrogen content on the absorption coefficient. Other possible reasons that might influence the enhanced optical absorption such as strain induced changes of α and light scattering effects are also discussed and explicitely excluded by appropriate experiments to be the essential enhancement reasons.
Role of Hydrogen for Microcrystalline Silicon Formation
Authors: Saitoh K. , Kondo M. , Fukawa M. , Nishimiya T. , Futako W. , Shimizu I. , Matsuda A. 
Published: April 2011

ABSTRACTThe role of hydrogen atoms in the formation process of hydrogenated microcrystalline silicon (μc-Si:H) by plasma enhanced chemical vapor deposition method has been investigated. Under the present conditions, the etching and the permeation of hydrogen atoms in the subsurface region do not cause the crystallization. The kinetics study of surface morphology and structure in the initial growth of μc-Si:H on an atomically flat substrate indicates that the onset thickness of island coalescence reduced under μc-Si:H formation condition. The results support the ‘surface diffusion model’ in which the surface diffusion of film precursors is enhanced by the sufficient hydrogen coverage of surface and by hydrogen atom recombination energy on the growing surface of the film.
A Fully Self-Aligned Amorphous Silicon Tft Technology for Large Area Image Sensors and Active-Matrix Displays
Authors: Powell M J , Glasse C , Curran J E , Hughes J R , French I D , Martin B F 
Published: April 2011

ABSTRACTWe have developed a fully self-aligned amorphous silicon TFT technology, which is suitable for large area image sensors and active matrix displays. Self-alignment is achieved by defining the top nitride by back exposure and then forming source and drain contacts by ionimplantation and silicidation. We incorporate a low resistance gate metallisation process, by using Al metal, capped by Cr. We have compared the process of forming the silicide after the ion-implantation step, with a new process of forming the silicide first and then implanting through the formed silicide. We find a significant advantage to the latter method, where we can achieve a higher doping level and reduced contact resistance. We have therefore optimised our process based on this method. Transistor characteristics as a function of channel length for both methods show the improved contact resistance, obtained with the latter method. We obtain field effect mobilities of 0.7cm2V−1s−1, measured in the saturated region, for a channel length of 8μm.
Electronic Properties of Hot-Wire Deposited Nanocrystalline Silicon
Authors: Brüggemann R. , Hierzenberger A. , Wanka H.N. , Schubert M.B. 
Published: April 2011

ABSTRACTWe compare the electronic properties of nanocrystalline silicon from hot-wire chemical vapor deposition in a high-vacuum and an ultra-high-vacuum deposition system, employing W and Ta as filament material. From the constant photocurrent method we identify a band gap around 1.15 eV while, in contrast, a Tauc plot from optical transmission data guides to a wide band gap above 1.9 eV. The sudden change-over from nanocrystalline to amorphous structure in a hydrogen dilution series is also find in the dark and photoconductivity measurements. The samples show a metastability effect in the dark conductivity upon annealing in vacuum with an increase in the dark conductivity, with the large dark conductivity decreasing slowly after the annealing cycle when the cryostat is flushed with air. We identify larger values for the mobility-lifetime products, which corresponds to the smaller defect density shoulder in constant photocur- rent spectra, for the ultra-high-vacuum deposited material compared to the high-vacuun counterpart.
Structural Properties of Polycrystalline Silicon Films Formed by Pulsed Rapid Thermal Processing
Authors: Wang Yongqian , Liao Xianbo , Diao Hongwei , He Jie , Ma Zhixun , Yue Guozhen , Sheng Shuran , Kong Guanglin , Zhao Yuwen , Li Zhongming , Yun Feng 
Published: April 2011

ABSTRACTA novel pulsed rapid thermal processing (PRTP) method has been used for realizing the solid-phase crystallization of amorphous silicon films prepared by PECVD. The microstructure and surface morphology of the crystallized films are investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The results indicate that this PRTP is a suitable postcrystallization technique for fabricating large-area polycrystalline silicon films with good structural qualities such as large grain size, small lattice microstain and smooth surface morphology on low-cost substrate.
Polycrystalline Silicon Single Electron Island by Excimer Laser Irradiation on a-Si Film
Authors: Park C-M , Jeon J-H , Lim M-S , Yoo J-S , Han M-K 
Published: April 2011

ABSTRACTWe propose a novel fabrication method for a room temperature operating single-electron memory using the size and location controlled poly-Si island by lithographic technique and excimer laser annealing.We have patterned tip shaped excimer laser windows and irradiated laser energy through windows for crystallizing amorphous silicon. As a result of laser energy, the poly-Si grains are growing from patterned window side so that the fine grain and isolated large poly-Si quantum dot are inherently formed by well-known ACSLG regime. The oxidation was then performed by RTP at 950 °C for 30 seconds in order to isolate quantum island and fine poly-Si grains for quantum dot. The peaks of the poly-oxide along the poly-Si grain boundaries were lowered during that oxidation and isolated the poly-Si grains and made oxide barriers.
Silicon Nanowire: a New Shape of Crystalline Silicon
Authors: Zhang Y.F. , Tang Y.H. , Wang N. , Lee C. S. , Yu D.P. , Bello I. , Lee S.T. 
Published: April 2011

ABSTRACTSilicon nanowires have been synthesized by using a high-temperature laser ablation method. Transmission electron microscopic investigation shows that the nanowires are crystalline Si, and have diameters ranging from 3 to 43 nm and lengths up to a few hundreds μm. Raman scattering spectrum shows an asymmetric peak at the same position as that of bulk crystalline silicon. The x-ray diffraction revealed an important contribution from surface oxide. This is due to the high surface-to-volume ratio. Visible photoluminescence (PL) was observed in nanowires with sub-5 nm diameter.
Low-Temperature PECVD Polysilicon Crystallization by Rapid Thermal Processing
Authors: Stewart Mark , Hovagimian Howard , Arakkal Jecko , Saha Sambit , Hatalis Miltiadis K. 
Published: April 2011

AbstractThis work investigates the solid phase crystallization of PECVD amorphous silicon films by rapid thermal processing (RTP) as an alternative to laser crystallization. It is shown that PECVD films can be crystallized by RTP at temperatures compatible with glass substrates. A statistical design approach was used to investigate the effect of the various deposition and annealing conditions on the crystallization temperature, material properties and TFT device performance. The investigated variables include deposition temperature, rf power, pressure, surface treatments, dehydrogenation treatment, source gas, dilutant gas, and RTP scan speed. Important deposition and crystallization parameters will be discussed regarding polysilicon film optimization.
A Dehydrogenation and Annealing Method of a-Si by Microwave
Authors: Park C-M , Jeon J-H , Kim C-H , Han M-K 
Published: April 2011

AbstractWe propose a new method for selective crystallization of amorphous silicon and source/drain ion impurities activation by microwave annealing. We have measured FTIR to investigate hydrogen content variation in PECVD a-Si film and examined the poly-Si grain structure by SEM. We have also observed the Raman spectroscopy in order to investigate the grain growth mechanism during microwave annealing.In our experiment, a-Si layer between microwave absorbing layers was fully crystallized in 60 seconds and hydrogen content of a-Si under microwave reflective layer was not varied after 20 minutes microwave annealing. These results indicate that proposed method may be implemented for fabricating a-Si and poly-Si TFTs on the same glass substrate. We have fabricated the poly-Si and a-Si TFTs employing microwave annealing for active layer crystallization and source/drain activation by our method.
Controlling the Amount of Si-OH Bonds for the Formation of High-Quality Low-Temperature Gate Oxides for Poly-Si TFTs
Authors: Yuda Katsuhisa , Tanabe Hiroshi , Sera Kenji , Okumura Fujio 
Published: April 2011

AbstractLowering process temperatures for polysilicon thin-film-transistors (TFTs) has given rise to new worries about the quality of TFT gate oxides. Specifically, presence of large amounts of SiOH bonds in gate oxides has become a matter of concern. We discuss methods for suppressing the formation of Si-OH bonds during chemical vapor deposition (CVD) of low-temperature processed (LTP) gate oxides. The use of remote-plasma CVD and control of the reaction between the silicon source gas and the oxygen source gas are both shown to be effective. We also show that decreased amounts of Si-OH bonds in LTP-CVD gate oxides result in desirable decreases in fixed oxide charge densities.
Mechanism of Field Emission in Diamond and Diamond-Like Carbon
Authors: Robertson J 
Published: April 2011

AbstractIt is shown that the facile electron field emission from diamond and diamond-like carbon occurs because surface groups such as C-H can produce large changes in electron affinity, so that electric fields from the anode can be focused towards unhydrogenated surface areas of high affinity, the fields ending on negative charges in an underlying depletion layer. The resulting downwards band bending creates very large fields which cause Fowler-Nordheim emission, while not exceeding the breakdown field, which is the highest for any solid.
A Bistable Membrane Approach to Micromachined Displays
Authors: Fleming J.G. 
Published: April 2011

AbstractThe fabrication of bistable membrane structures with potential application to projection displays has been demonstrated. The use of a thin film in heavy compression combined with a central pivot point enables the fabrication of devices with two mechanically stable orientations. The demonstration structure consisted of a silicon dioxide membrane, a thin silicon nitride fillet pivot and thin aluminum electrodes. Polysilicon was used as the sacrificial material.
Correlation of Performance and Hot Carrier Stress Reliability of Polycrystalline Silicon Thin-Film Transistors With Substrates and Substrate Coating
Authors: Wang Y. Z. , Awadelkarim O. O. 
Published: April 2011

AbstractWe report on the performance and hot carrier stress (HCS) reliability of n-channel poly-Si TFTs fabricated on bare or SiO2-coated low-alkali glass, or fused silica substrates. Low-pressure chemical vapor deposited (LPCVD) SiO2 films with different thicknesses are used as impurity diffusion barrier layers. We have found that the performance and HCS reliability of n-TFTs on the SiO2-coated glass are superior to those of n-TFTs on bare glass, and comparable to those of TFTs on fused silica. We also explore the impact of the SiO2 coating thickness on the performance and HCS reliability of the TFTs. The HCS reliability of the TFTs on SiO2-coated glass substrates is observed to depend on the SiO2 coating thickness. This is explained in terms of a phenomenological model which involves impurity and grain boundary traps.
Characterization of Secondary Electron Emission from Materials with Low or Negative Electron Affinity
Authors: Yater J.E. , Shih A. 
Published: April 2011

AbstractSecondary electron emission spectroscopy is used to examine the emission characteristics of diamond films as a function of the bulk and surface properties. We find significant variation in the secondary electron yields measured from diamond surfaces even when energy distribution measurements indicate that a low or negative electron affinity is present. In particular, we observe that the material properties, such as bulk and surface uniformity, surface composition, and impurity and defect concentrations, have a strong affect on the secondary electron yield measurements. Furthermore, the energy distribution of the emitted electrons is found to vary with adsorbate species. In certain cases, the energy distribution changes with adsorbate coverage even though the measured electron intensity remains unchanged. From an analysis of the data, we identify bulk and surface properties needed to optimize the emission characteristics.
Voltage Dependent Field Emission Energy Distribution Analysis of Wide Bandgap Materials
Authors: Mccarson B.L. , Schlesser R. , Sitar Z. 
Published: April 2011

AbstractField emission from wide bandgap materials was investigated through voltage dependent field emission energy distribution (V-FEED) analysis. As compared to classical I-V characterization, V-FEED analysis can provide additional, detailed information about the origin of and the mechanism responsible for the field emission of electrons. The V-FEED technique consists of measuring the energy distribution of field emitted electrons collected at various extraction voltages. By measuring changes in the energy of the field emission peak at different voltages, data can be extrapolated to flat-band condition to determine the energy of the band from which the electron emission originated. In this study, field emission from cubic boron nitride (c-BN) coated and diamond coated tip-shaped Mo emitters was examined. For the nominally intrinsic wide bandgap coating materials studied, a linear voltage drop across the wide bandgap material, usually on the order of 1% of extraction voltage was observed and explained by field induced band-bending. For the intrinsic c-BN and diamond samples studied, the electron emission originated from the conduction band minimum at the wide bandgap material/vacuum interface.
Effect of SP3/(SP2+SP3) Carbon Fraction on the Photoelectric Threshold and Electron Affinity of Diamond Films
Authors: Akwani I.A. , Sosa E.D. , Lim S.C. , Stallcup R.E. , Castillega J.N. , Bernhard J. , Golden D.E. , Perez J.M. 
Published: April 2011

AbstractWe report a significant decrease in the photoelectric threshold of chemical vapor deposition grown diamond films as the fraction of sp3 carbon to sp2 plus sp3 carbon in the films decreases. Raman spectroscopy and x-ray photoelectron spectroscopy are used to characterize the different forms of carbon in the films and the sp3/(sp2 + sp3) carbon fraction at the surface. We observe a decrease in the photoelectric threshold from 4.5 eV to 3.9 eV as the sp3/(sp2 + sp3) carbon fraction at the surface decreases from 71% to 55%. Ultraviolet photoelectron spectroscopy of the films shows that they have a negative electron affinity surface. Therefore, the work function of the films decreases from 4.5 eV to 3.9 eV. We propose that the decrease in photoelectric threshold is due to a decrease in the band gap of sp2-sp3 carbon networks at the grain boundaries. The observed decrease in photoelectric threshold can be used to tailor the electronic properties of diamond films for specific applications.
Morphology of Low Temperature Carbon Films Prepared by VHF CVD: Correlation with Field Emission
Authors: Titkov A.N. , Kosarev A.I. , Vinogradov A.J. , Waqar Z. , Makarenko I.V. , Felter T. 
Published: April 2011

AbstractThe effect of deposition parameters and substrate on the morphology of carbon films prepared in VHF plasma at low temperature has been studied by Atomic Force Microscopy. Carbon films demonstrating superior emission characteristics were the smoothest, but not all of the smoothest films demonstrated good emission. Significant influence of pre-growth treatment of the substrate surface on the emission characteristics of the films was found.
Advanced CVD Diamond Microtip Devices for Extreme Applications
Authors: Patterson D.E. , Jamison K.D. , Kempel M.L. , Freeman S. 
Published: April 2011

AbstractExtreme Devices has fabricated and tested gated CVD diamond microtip arrays for use as cold cathodes in a variety of high power, high temperature, and high radiation applications. The uses for these devices include direct replacement of hot filament cathodes, microwave amplifiers, spaceborne sensors, and other areas requiring devices that provide high current output and that will function in harsh environments. The basic architecture of the device including an overview of the method for obtaining the self-aligned gated diamond microtip array is presented. Key developments for these robust devices include low electron extraction fields (3 V/μm), high current density output (>75A/cm2), stable operation for long periods of time, and operation in severe (high pressure) conditions. The gated cathodes offer low turn-on voltages (22 V) and appear to be well suited to a number of applications.
Relationship of Field Emission Characteristics on Process Gas Nitrogen Content in Nitrogen Doped Diamond Films
Authors: Sowers A.T. , Ward B.L. , Nemanich R.J. 
Published: April 2011

AbstractThis study explores the field emission properties of nitrogen doped diamond grown by microwave plasma CVD. Several diamond samples were grown on silicon under varying conditions. With certain process parameters, films can be grown which exhibit photoluminescence bands at 1.945eV and 2.154eV that are attributed to single substitutional nitrogen. Field emission characteristics were measured in ultrahigh vacuum with a position variable anode. For samples grown with gas phase [N]/[C] ratios less than 16, damage from micro-arcs occurred during the field emission measurements. Samples grown at higher [N]/[C] content could be measured without damage. These measurements indicate relatively high threshold fields (>100V/νm) for electron emission. From the data, two possible field emission mechanisms are presented. Conducting defect states in the bandgap of diamond may provide a source of electrons to the emitting diamond surface.
Ion Beam Techniques for Low K Materials Characterization
Authors: Bakhru H. , Kumar A. , Kaplan T. , Delarosa M. , Fortin J. , Yang G.-R. , Lu T.-M. , Kim S. , Steinbruchel C. , Tang X. , Moore J. A. , Wang B. , McDonald J. , Nitta S. , Pisupatti V. , Jain A. , Wayner P. , Plawsky J. , Gill W. , Jin C. 
Published: April 2011

ABSTRACTIon beam analysis techniques have become very useful for characterization of low k materials. Studies on several ion beam analysis techniques will be discussed. Rutherford Backscattering Spectrometry (RBS) provides a very powerful analytical technique for the thickness and porosity measurements on porous Si0 2 films. Nuclear Reaction Analysis (NRA) techniques for hydrogen and fluorine profiling are very useful to characterize fluorinated polymer and fluorinated oxide films. Examples of low k materials including Si02:F, Parylene-AF and Teflon-AF will be discussed. Fluorine diffusion in to metals and various interface effects between metal and low k materials will be presented.