bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Electronic Structure, Metastability and Transport Properties of Optimized Amorphous Silicon-Germanium Alloys
Authors: Chen Chih-Chiang , Lubianiker Yoram , Cohen J. David , Yang Jeffrey C. , Guha Subhendu , Wickboldt Paul , Paul William 
Published: April 2011

ABSTRACTWe have carried out a comprehensive study of the electronic properties of two series of optimized a-Si1−xGex:H alloys fabricated at United Solar Systems Corporation (“Uni-Solar”) and Harvard University, encompassing the composition range 0.2 ≤ × ≤ 1.0. Both series of samples exhibit deep defect densities that obey quite accurately the spontaneous bond-breaking model proposed by M. Stutzmann which, by considering how the defect formation energy varies with the position of Fermi energy, we have been able to extend to doped samples.We have also extended our studies to include measurements of ambipolar diffusion lengths and the effects of light-induced degradation, and thus have been able to demonstrate a direct relation between these transport properties and the measured defect levels before and after degradation.
Deep Defect Relaxation in Hydrogenated Amorphous Silicon: New Experimental Evidence and Implications
Authors: Cohen J. David , Zhong Fan , Kwon Daewon , Chen C.-C. 
Published: April 2011

ABSTRACTWe review modulated photocurrent experiments which indicate that thermal emission rate for Do defects in intrinsic samples varies in response to changes in the Fermi-level or quasi-Fermi position. This apparent shift in energy threshold is confirmed using time resolved sub-band-gap spectroscopy. We also demonstrate that such a variation of emission rate with changes in the Fermi-level position, if present within the depletion region near a barrier junction, is consistent with the details of the temperature dependence of the junction capacitance in intrinsic samples.
Possible Origin of Large Response Times and Ambipolar Diffusion Lengths in Hot-Wire-Cvd Silicon Films
Authors: Schwarz R. , Múrias T. , Conde J.P. , Brogueira P. , Chu V. 
Published: April 2011

ABSTRACTWe measured the response time zR and the ambipolar diffusion length Lamb in amorphous (a-Si:H) and microcrystalline silicon films (μ-Si:H) prepared by hot-wire chemical vapor deposition (HW-CVD). The response times in the amorphous and microcrystalline HW films were larger by factors of 100 and 1000, respectively, than in standard PE-CVD a-Si:H films (1-2 μs). The ambipolar diffusion length of the HW-CVD films was about twice as large as in conventional glow-discharge films. Strong doping of microcrystalline HW films with trimethylboron (TMB) led to a reduction of the response time. The results hint to a positive effect of the compact microstructure of HW-CVD films. We suggest the dark conductivity activation energy, Eact, and response time, τR, to be used as suitable parameters to describe optoelectronic film properties.
Influence of the H2 Dilution And Filament Temperature on the Properties of P Doped Silicon Carbide Thin Films Produced by Hot-Wire Technique
Authors: Ferreira I. , Águas H. , Mendes L. , Fernandes F. , Fortunato E. , Martins R. 
Published: April 2011

ABSTRACTThis work deals with the role of hydrogen dilution and filament temperature on the morphology, structure and electrical properties of nanocrystalline boron doped silicon carbide thin films produced by hot-wire technique. The structural and morphological data obtained by XRD, SEM and micro-Raman show that for filament temperatures and hydrogen dilutions above 2100°C and 90%, respectively, the surface morphology of the films is granular with a needle shape, while for lower filament temperatures and hydrogen dilutions the surface morphology gets honeycomb like. The SIMS analysis reveals that films produced with filament temperatures of about 2200°C and hydrogen dilution of 99% present a higher hydrogen and carbon incorporation than the films produced at lower temperatures and hydrogen dilutions. These results agree with the electrical and optical characteristics recorded that show that the films produced exhibit optical gaps in the range from 1.8 to 2 eV and transverse conductivities ranging from 10−1S/cm to 10−3 S/cm, consistent with the degree of films crystallinity and carbon incorporation recorded.
Deposition, Defect and Weak Bond Formation Processes in a-Si:H
Authors: Robertson J , Powell M J 
Published: April 2011

ABSTRACTThe growth of a-Si:H and the resulting weak bond and defect formation mechanism is analysed in terms of the adsorbed Sill3 model of growth. It is found that this model describes the surface processes well, but it needs further development to correctly describe the temperature dependence of the formation of defects and weak bonds, since the surface defect density decreases monotonically with temperature and does not show a minimum near 250C. We show that the experimentally observed increase in hydrogen content, weak bond and defect density at lower deposition temperatures can be accounted for by a hydrogen evolution reaction from H2* sites.
Microcrystalline Silicon n-i-p Solar Cells Deposited Entirely by the Hot-Wire Chemical Vapor Deposition Technique
Authors: Wang Qi , Iwaniczko Eugene , Mahan A. H. , Williamson D. L. 
Published: April 2011

ABSTRACTWe describe a series of microcrystalline (μc) silicon n-i-p solar cell devices fabricated entirely by the hot-wire chemical vapor deposition technique. These devices are deposited on flat stainless-steel at a substrate temperature below 250°C, and are evaluated using solar-cell performance and quantum-efficiency (QE) measurements. We explore the effect of crystallite size, as examined by X-ray diffraction, by varying the hydrogen-to-silane ratio from 5 to 40, while keeping the μc-n and the μc-p layers the same. We find a significant blue shift of the QE peak and an enhancement of red response compared with a standard a-Si:H solar cell. The blue shift increases with increasing hydrogen-to-silane ratio. We attribute this shift to the i-layer becoming more n-type with increasing hydrogen dilution. We also use a hydrogen gas purifier and find a large improvement in device performance.
Effect of Filament Bias on the Properties of Amorphous and Nanocrystalline Silicon from Hot-Wire Chemical Vapor Deposition
Authors: Wanka H.N. , Brüggemann R. , Köhler C. , Zrinscak I. , Schubert M.B. 
Published: April 2011

ABSTRACTAt the high temperatures during hot-wire assisted chemical vapor deposition, ther- mal emission of electrons from the filament occurs. We studied the effect of filament bias, and thus the filament-to-substrate current, on the structural, electronic and optical properties of amorphous and nanocrystalline silicon deposited by this method. The current drawn by the substrate can be varied by many orders of magnitude as thermally emitted electrons are increasingly collected with applied bias voltage. The crystallinity of the nanocrystalline samples is not affected by the bias voltage. The defect density in amorphous silicon is affected by the electron bombardment at high bias voltage only, for which we also find a significant reduction in the mobility-lifetime product from steady-state photoconductivity.
Direct Nucleation and Selective Growth of Nuclei for High Crystallinity Poly-Sige Thin Films on Sio2 Substrates
Authors: Hanna Jun-ichi , Shiota Kunihiro , Yamamoto Masaji 
Published: April 2011

ABSTRACTWe have proposed a new technique for high crystallinity polycrystalline SiGe thin films with homogeneous crystallinity. The key technologies, i.e., direct nuclei formation on the substrate surface and selective growth of the resulting nuclei to gains, were established irrespective of film composition in a reactive thermal CVD with GeF4 and Si2H6. High crystallinity poly-Si0.05Ge0.95 thin films could be obtained on SiO2 substrates at 375°C and poly-Si0.95Ge0.05 thin films at 450°C by simply tuning the growth pressure for selective growth of the nuclei after creating the nuclei on the substrates. We demonstrated that not only the crystallinity but also the electrical properties of the resulting films were improved very much compared with those of continuously grown films.
High Quality Hydrogenated Amorphous Silicon Films with Significantly Improved Stability
Authors: Sheng Shuran , Liao Xianbo , Ma Zhixun , Yue Guozhen , Wang Yongqian , Kong Guanglin 
Published: April 2011

ABSTRACTHigh quality hydrogenated amorphous silicon (a-Si:H) films have been prepared by a simple “uninterrupted growth/annealing” plasma enhanced chemical vapor deposition (PECVD) technique, combined with a subtle boron-compensated doping. These a-Si:H films possess a high photosensitivity over 106, and exhibit no degradation in photoconductivity and a low light-induced defect density after prolonged illumination. The central idea is to control the growth conditions adjacent to the critical point of phase transition from amorphous to crystalline state, and yet to locate the Fermi level close to the midgap. Our results show that the improved stability and photosensitivity of a-Si:H films prepared by this method can be mainly attributed to the formation of a more robust network structure and reduction in the precursors density of light-induced metastable defects.
Reflective Infrared Spectra of PECVD Thin Films on Glass Substrate
Authors: He Shusheng 
Published: April 2011

AbstractIn order to use a reflective FTIR measurement to evaluate thin films deposited on glass substrate, we have to consider several important factors, such as surface polarization, phase shift, and interference from different interfaces. PECVD thin films, oxide, nitride and a-Si:H deposited on top of the glass substrate are discussed by the reflective FTIR measurement.
Substrate Surface Morphology and Growth Evolution of Low Temperature Silicon Nitride on Transparent Plastics
Authors: Smith L. L. , Arthur C. B. , Yang C. S. , Parsons G. N. 
Published: April 2011

AbstractSurface morphology and nucleation are important for forming electronic thin films on plastic substrates. We have used atomic force microscopy (AFM) with an oscillating cantilever to examine various transparent substrates, including 7059 glass, polyethylene terephthalate (PET), indium tin oxide (ITO)-coated PET, and polycarbonate, and studied the effect of deposition processes on these surfaces. Studies include: 1) differences in dielectric nucleation on plastics and glass; 2) dielectric growth evolution; and 3) the effect of plasma exposure on surface roughness. The surface morphology of the different substrate materials varied significantly with the PET showing the largest roughness values; all the polymers were more rough than typical 7059 glass (rms <0.5 nm). Furthermore, the initial nucleation on both polymers were different than on glass. Very thin layers (<30Å nominal thickness) of plasma deposited silicon nitride films on polycarbonate and glass produced flat, smooth surfaces, with rms roughness of ≈0.5 nm. On the PET substrates, the nitride growth began with broad, thin deposits and developed a coarse, large-grained structure as growth progressed. With exposure to a NH3 + N2 plasma, the glass and PET surfaces showed detectable changes in surface roughness, which are discussed below. These results demonstrate that plasma-deposited insulators nucleate and grow differently on plastic substrates than on glass, which has implications for electronic devices fabricated directly on plastics.
Low-Voltage Cathodoluminescent Properties of Blue-Emitting Yttrium Silicates Doped With Cerium
Authors: Bosze E. J. , Hirata G. A. , Mckittrick J. , Shea L. E. 
Published: April 2011

AbstractYttrium silicate activated with Ce3+, (Y1−xCex)2SiO5, has been found to be an efficient phosphor that can potentially be used as the blue-emitting component in field emission flat panel displays. This highly refractory powder can be synthesized by combustion synthesis, a low cost technique used to fabricate multicomponent oxide powders in a single step process. The effect of activator concentration and post-synthesis annealing was examined on the fluorescent properties. The powders were found to be monoclinic space group P21/c in the as-synthesized state, and transformed to monoclinic space group C2/c after annealing. The maximum luminous emission intensity was reached after a one hour anneal at 1350°C for x=0.0075, with the peak Ce3+ emission wavelength between 420 and 450 nm. When co-doped with Gd3+, no increase in the emission intensity was observed.
Hillock Formation and Reduction Using Metal Interlayers for Active Matrix Display Applications
Authors: Saha Sambit K. , Howell Robert S. , Hatalis Miltiadis K. 
Published: April 2011

AbstractThe effects of using an extra layer of nickel, cobalt or titanium with Al-1%Cu films were examined with regard to hillock formation. The density and sizes of hillocks in these double layer metallization structures were characterized using scanning electron microscopy (SEM) and interfacial reactions between the transition metal layer and Al-l%Cu were examined using glancing angle x-ray diffraction (GA-XRD). Resistivities of the double layer films were characterized using conventional 4-point probe measurements. Hillock formation was totally suppressed when Ni and Co was used as the transition metal, while Ti did not eliminate hillocks. Hillock formation and resistivities are explained on the basis of interfacial reactions.
High Conductivity Gate Metallurgy for TFT/LCD's
Authors: Fryer Peter M. , Colgan E. , Galligan E. , Graham W. , Horton R. , Jenkins L. , John R. , Kuo Y. , Latzko K. , Libsch F. , Lien A. , Nywening R. , Polastre R. , Rothwell M. E. , Wilson J. , Wisnieff R. , Wright S. 
Published: April 2011

AbstractAmorphous silicon based thin film transistor liquid crystal displays (TFT/LCD) have become the dominant technology used for flat panel displays for notebook computers. The need for higher resolution, larger diagonal displays for both notebook and desktop applications is discussed. Calculations have shown that the use of high conductivity gate metal such as aluminum or copper, together with the implementation of improved groundrules, can significantly extend today's technology. Aluminum suffers from problems with hillock formation during PECVD processing, and copper typically has poor adhesion to glass, reaction problems with silicon and other PECVD films, and difficulties in contacting it to other metals. Approaches to solving problems with both materials are presented, and a novel reduced mask process to fabricate high resolution, high aperture ratio 10.5” SXGA (1280 × 1024) displays is described. The process uses copper gate metallurgy with redundancy, without the need for extra processing steps. The resulting displays have 150 dpi color resolution, an aperture ratio of over 35%, and excellent image quality, making them the first high resolution displays that are suitable for notebook applications.
Boron Nitride Emitters
Authors: Pryor R. W. , Li Lihua , Minina G. , Busta H. H. 
Published: April 2011

AbstractNew observations are presented on the emission of electrons from n-type boron nitride (BN) cold cathode films. These carbon-doped BN films demonstrate a significant improvement in the electron emission current, on the order of 1 to 3 orders of magnitude, as a function of the extraction field for many different materials and morphologies.These BN cold cathodes have yielded stable DC currents in excess of 4 mA at an extraction field of approximately 30 V/μm.
Emission and Processing Requirements for Carbide Films on Mo Field Emitters
Authors: Mackie W. A. , Xie Tianbao , Matthews M.R. , Davis P. R. 
Published: April 2011

AbstractWe have been working for many years on electron emission and surface properties of transition metal carbides. These studies have covered field, photo, and thermionic emission from bulk carbides as well as field and photo emission from carbide coatings and films on various substrates. Thin film carbide overcoatings have also been used on field emitter arrays of both Mo and Si. These unique carbide materials have electron emission properties making them attractive candidates for several applications. Uses for these carbides include FEA video displays, microwave applications, high current and small spot electron sources (e.g. accelerators and FELs), and cold cathodes for operation at tube pressures and in poor vacuums (e.g. FEAs, vacuum detectors, and neutralizing beams for ion thrusters).We report here on one aspect of our current research which deals with electron emission of ZrC films coating single Mo field emitters. The relevant application is Spindt-type field emitter arrays. Processing steps are evaluated showing the need for a clean substrate. After deposition treatments are also investigated. Emission degradation has been noted after exposure to air and we report on successful use of a hydrogen atmosphere to reverse those adverse effects.
Characteristics of Surface-Emitting Cold Cathode Based on Porous Polysilicon
Authors: Komoda Takuya , Sheng Xia , Koshida Nobuyoshi 
Published: April 2011

AbstractIt is demonstrated that porous polysilicon (PPS) diode fabricated on the silicon substrate operates as efficient and stable surface-emitting cold cathode. A 1.5 pm of non-doped polysilicon layer is formed on n-type (100) silicon wafer and anodised in a solution of HF(50%): ethanol = 1:1 at a current density of 10 mA/cm2 for 30 seconds under illumination by a 500W tungsten lamp from a distance of 20 cm. Subsequently, PPS layer is oxidized in a rapid thermal oxidation(RTO) furnace for one hour at a temperature of 700°C. A semi-transparent thin Au film (about 10 nm thick) is deposited onto the PPS layer as a positive electrode and an ohmic contact is formed at the back of the silicon wafer as a negative electrode. When a positive bias is applied to the Au electrode in vacuum, the diode uniformly emits electrons. No electron emission is observed in the negatively biased region. Emission current is about 10−4 A/cm2 at 20V bias, and no fluctuation of emission current is observed as a function of time. Emission current is not affected by a surrounding pressure up to around 10 Pa. It is envisaged that mechanism of this emission is attributed to hot electron tunnelling.
Field Emission from Low Temperature Carbon Coated Silicon Tips
Authors: Kosarev A.I. , Zhirnov V.V. , Vinogradov A.J. , Shutov M.V. , Bormatova L.V. , Givargizov E.I. , Felter T.E. 
Published: April 2011

AbstractField emission from silicon tips with carbon coatings deposited by VHF CVD at low temperature, Ts=225°C, has been studied. Emission was measured from both single tips and tip arrays. Structure and electronic properties of the films have been characterized. Significant effects due to pregrowth plasma treatment of the sample surface were observed on microstructure and emission characteristics. Optimized carbon coatings on silicon tips increased emission current by about two orders and reduced the threshold field to 0.1 V/μm.
New Lateral Field Emitter Arrays Inherently Integrated with Thin Film Transistor
Authors: Lim Moo-Sup , Park Cheol-Min , Han Min-Koo , Choi Yearn-Ik 
Published: April 2011

AbstarctWe have fabricated a new three-terminal lateral field emitter structure in which the anode current is limited by the channel current of undoped region. The new device exhibits an excellent stability of the emission current. The field emission characteristics of fabricated device have two modes. In the first mode below 89 V, the mechanism of emission is identical to that of conventional poly-Si emitters and, in the second mode above 89 V, the emission current is limited by the inversion charges in the channel, so stable anode current is maintained. Furthermore, the fabrication process of the device is very simple.
Dielectric Properties of Glass Capillary Arrays
Authors: Huber T. E. , Silber Leo , Boccuzzi Frank 
Published: April 2011

ABSTRACTGlass Capillary Arrays (GCA) are low density columnar monolithic structures made of soda-lime glass. This structure, in which 76% of volume between the columns, the channels, is void, also has a greatly reduced dielectric constant in comparison with bulk glass. We have measured the index of refraction and absorption of samples of GCA's in the X-band, 8 × 109 Hz to 1.2×1010 Hz, for various orientations of the channels with respect to the polarization. For channels perpendicular to the polarization direction we have measured an index of refraction of 1.15. In comparison the index of refraction of (bulk) soda-lime glass is 2.6. We also examined the absorption in the far-infrared (FIR) frequency range between 6×1011 Hz and 6×1012 Hz. In this frequency range we obtain a k2 dependence due to losses in the glass matrix at higher frequencies. The results of the X-band and FIR results are interpreted in terms of an effective medium theory of the real and imaginary part of the dielectric constant of the composite.
Integration Issues for Diamond Like Carbon in a Copper Damascene Process Flow
Authors: Grill A. , Jahnes C. , Patel V. , Ott J. , Hummel J. , Mih R. , Liu J. 
Published: April 2011

ABSTRACTHydrogenated “diamondlike” carbon (DLC) is a potential candidate as a low k material for the back end interconnect (BEOL) dielectric for VLSI chips. The DLC material is an attractive dielectric due to its isotropic properties and the ability to deposit the films by CVD techniques, such as PECVD or HDP systems. Under suitable preparation conditions such materials can reach dielectric constant values below 2.8, even as low as 2.4. While the as-deposited films are not stable to exposure to subsequent processing temperatures of about 400 C, it appears that they can be stabilized, in terms of dimensional stability and material loss, by an initial anneal.The integration of DLC films in the BEOL structure further requires good adhesion with the materials in contact with the DLC dielectric, such as silicon nitride or silicon oxide, and liner metallurgy. As the potential application of the DLC films will be in Cu based damascene structures the behavior of the films under CMP conditions is also important.The talk will discuss the evaluation of DLC films and of integration issues such as adhesion under processing conditions, patterning, CMP behavior. Blanket and patterned structures built with DLC films will be presented.
Copper damascene using low dielectric constant fluorinated amorphous carbon interlayer
Authors: Matsubara Y. , Endo K. , Iguchi M. , Ito N. , Aoyama K. , Tatsumj T. , Horiuchi T. 
Published: April 2011

ABSTRACTWe have developed a new interconnect technique using a low-k (εt,=2.5) organic interlayer (fluorinated amorphous carbon: a-C:F) and a low-resistivity metal line (copper). The new technique attains a duction in both the capacitance of the interlayer and the resistance of the metal line. We found that a-C:F on Cu reduces reflection to 10% for Kr-F line lithography. However, a-C:F cannot act as a protection layer for oxidation even at 200°C in atmospheric ambient annealing. Cu diffusion into a-C:F is about 100 nm at the annealing temperature of 450°C. The resistivity of the Cu line is 2.3–2.4 μΩ · cm for the 0.5-μm line width. Although the leakage current of the a-C:F ILD is one order higher than that of the SiO2 ILD, electrical isolation is acceptable at < 20 V when annealing is carried out at 350°C in a vacuum.
Stability Of Silicon-Oxygen-Fluorine And Carbon-Fluorine LOW-K DIELECTRICS WITH RESPECT TO ATTACK BY WATER
Authors: Yang H. , Lucovsky G. 
Published: April 2011

ABSTRACTAb initio configuration interaction calculations have been previously used to account for the relatively large decreases in the static dielectric constant of Si-O-F alloys with low alloy concentrations of F-atoms, ∼ 22%for F concentrations of ∼ 10 at.%. The present study addresses the stability of these alloy films and carbon-fluorine films with respect to attack of Si-F bonds or C-F bonds by water molecules. The present calculations show that the reaction: H20 + 2 Si-F - 2 HF + Si-O-Si is exothermic by about 0.7 eV. However, the reaction of H20 + 2 C-F - 2 HF + CO-C is calculated to be endothermic by 1.6 eV. Our calculations focus on the reaction energetics and geometries as a function of the distance between the F-atoms of the Si-F and C-F groups and water molecule.