bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Plasma Treatment on Crystallization Behavior of Amorphous Silicon Films
Authors: Pangal K. , Sturm J.C. , Wagner S. 
Published: April 2011

ABSTRACTThe crystallization of amorphous silicon (a-Si:H) deposited by plasma enhanced chemical vapor deposition (PECVD) by thermal annealing is of great interest for display and silicon-on-insulator (SOI) technologies, though long anneal times (about 20 hrs) at 600 °C are typically required. We report that a room temperature hydrogen plasma exposure in a parallel plate diode type Reactive Ion Etcher (RIE) can reduce this crystallization time by a factor of five. This plasma enhanced crystallization can be spatially controlled by masking with patterned oxide, so that both amorphous and polycrystalline areas can be realized simultaneously at desired locations. This effect is due to the creation of seed nuclei at the surface, which enhance crystallization rates.
Low Temperature Vibrational Properties of Amorphous Silicon
Authors: Crandall R. S. , Iwaniczko E. , Mahan A. H. , Liu X. , Pohl R.O. 
Published: April 2011

ABSTRACTWe present internal friction and shear modulus measurements of amorphous silicon (a-Si) and germanium (a-Ge) films. The temperature independent plateau in internal friction below 10 K, common to all amorphous solids, also exists in these films. However, its magnitude which depends critically on the deposition method is smaller than found for all other amorphous solids. In particular, hydrogenated a-Si with about 1 at. % H prepared by hot-wire chemical-vapor-deposition leads to an internal friction nearly three orders of magnitude smaller than observed for all other amorphous solids. The internal friction increases after the hydrogen is removed by effusion.
Absorption Strengths of Si-H Vibrational Modes in Hydrogenated Silicon
Authors: Beyer W. , Ghazala M.S. Abo 
Published: April 2011

ABSTRACTInfrared absorption data of various Si:H samples involving several series of a-Si:H films as well as µc-Si:H and c-Si:H samples were analyzed to obtain ratios of the absorption strengths A of the Si-H stretching modes at 2000 and 2100 cm−1 and of the Si-H wagging mode at 640 cm−1. Hydrogen effusion measurements were used to obtain the absolute values of A. The results suggest essentially equal absorption strengths for the two Si-H stretching modes and a ratio of wagging and stretching absorption strengths independent of hydrogen density NH. Films with predominant 2100 cm−1stretching absorption show a stronger sample dependence of A than observed for samples with predominant 2000 cm−1absorption. A slight increase of the absorption strength of the Si-H wagging and stretching modes with rising hydrogen concentration is observed for a-Si:H films and is attributed to the decrease of the refractive index. Enhanced A values of µc-Si:H samples compared to a-Si:H samples point to the presence of molecular hydrogen.
Performances of Nano/Amorphous Silicon Films Produced by Hot Wire Plasma Assisted Technique
Authors: Ferreira I. , Águas H. , Mendes L. , Fernandes F. , Fortunato E. , Martins R. 
Published: April 2011

ABSTRACTThis work reports on the performances of undoped and n doped amorphous/nano-crystalline silicon films grown by hot wire plasma assisted technique. The film's structure (including the presence of several nanoparticles with sizes ranging from 5 nm to 50 nm), the composition (oxygen and hydrogen content) and the transport properties are highly dependent on the filament temperature and on the hydrogen dilution. The undoped films grown under low r.f. power (≍ 4 mWcm−2) and with filament temperatures around 1850 °K have dark conductivities below 10−1Scm−1, optical gaps of about 1.5 eV and photo-sensitivities above 105, (under AM3.5), with almost no traces of oxygen content. N- doped silicon films were also fabricated under the same conditions which attained conductivities of about 10−2Scm−1.
Interconnect Capacitance Extraction in Large-Area a-Si Imaging Systems
Authors: Pham H.H. , Nathan A. 
Published: April 2011

ABSTRACTWe present a new numerical extraction method for the quasi-static parasitic coupling capacitances associated with geometric overlapping in amorphous silicon (a-Si) thin film transistors (TFTs) and interconnect addressing lines in large-area a-Si imaging systems. The capacitance is extracted using a recently developed computational technique, based on exponential expansion of the Green's function, which offers a quick and accurate means of computing the three-dimensional potential and electric field, and hence, the charge distribution and capacitance. The technique can be used for effectively dealing with the extreme geometry TFT and interconnect structures (where layer thicknesses are much smaller than the other physical dimensions), the floating potential of the glass substrate, and multidielectric media, all of which are typical to large-area a-Si imaging electronics.
NMR Detection of New Hydrogen Populations in Amorphous and Crystalline Silicon
Authors: Borzi R. , Cull T. S. , Fedders P. A. , Leopold D. J. , Norberg R. E. , Boyce J. B. , Johnson N. M. , Ready S. E. , Walker J. 
Published: April 2011

ABSTRACTDeuteron magnetic resonance (DMR) has been used to further examine hydrogen (deuteron) populations in amorphous-silicon (a-Si) and in n-type crystalline silicon (x-Si). In both a-Si and x-Si DMR shows central components arising at least in part from isolated molecular deuterium and sharp doublet features from Si-bonded hydrogen (D). Our new results include the observation in x-Si of molecule-specific DMR multiple echoes from trapped ortho-D2. A second new result is the observation in x-Si of a substantialn Si-bonded D population with splittings between 46 and 80 kHz and perhaps arising from (deuterated) hydrogen bond-centered and antibonding configurations.
Wandering Dangling Bond Model for Staebler-Wronski Effects
Authors: Ikeda Masatoshi , Kitagawa Akio , Suzuki Masakuni 
Published: April 2011

ABSTRACTA new model for Staebler-Wronski effects is proposed. Defect pairs of (D°:D+) or (D°:D°) as a precursor of neutral dangling bonds are produced by electron-phonon interactions. Most of the defect-pairs immediately rebond after creation, but some of them separate resulting in wandering dangling bonds. The separation and the wandering take place through bond-switching. When wandering dangling bonds collide, most of them make covalent bonds via defect-pairs. The rate equations based on these processes are given and annealing effects on photo-generated dangling bonds are studied.
Light-Excited Structural Instability of a-Si:H
Authors: Kong G.L. , Zhang D.L. , Yue G.Z. , Wang Y.Q. , Liao X.B. 
Published: April 2011

ABSTRACTWith the accumulation of experimental data, it has been recognized by many that the light-induced metastable change of a-Si:H, Staebler-Wronski effect (SWE), may be related to a structural instability of the whole a-Si:H network. However, direct evidence of such a structural change is still lacking. In the present paper, the efforts of our laboratory in this direction will be reviewed, including the light-induced changes of Si-H bond absorption, low frequency dielectric response, and an apparent photo-dilation effect.
Bonded Hydrogen Atom Participation in Metastable Defect Formation in Hydrogenated Amorphous Silicon
Authors: Lucovsky G. , Yang H. 
Published: April 2011

ABSTRACTThis paper proposes intrinsic reaction pathways for generation of metastable defects in hydrogenated undoped or intrinsic amorphous silicon (i-a-Si:H). Since these pathways involve only silicon (Si) and hydrogen (H) atoms, this approach is valid for device grade materials in which concentrations of oxygen (0) atoms, and nitrogen-hydrogen (N-H) groups are present at concentrations below about 1019 cm−3. Ab initio calculations demonstrate that the proposed generation pathway reactions are exothermic with relatively small reaction barriers (< 0.4 eV).
Effect of Nh3/SiH4 Gas Ratios of Top Nitride Layer on Stability and Leakage in a-Si:H Thin Film Transistors
Authors: Murthy R.V.R. , Ma Q. , Nathan A. , Chamberlain S.G. 
Published: April 2011

ABSTRACTIn this paper, we present measurement results of stability and leakage current characteristics in inverted staggered hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) for different compositions of the top (passivation) nitride (a-SiNx:H). Here, we varied the deposition parameters, i.e., the ammonia (NH3) to silane (SiH4) gas ratio, of the passivation material for fixed composition of the (nitrogen-rich) gate nitride. When stressed with a prolonged gate bias, the observed shift in both threshold voltage (VT) and leakage current was largest in samples where the gas ratio (R = NH3/SiH4) was small. In the samples considered, R varied from 5 to 25. The shift in VT can be attributed to injection of energetic carriers from the a-Si:H and their subsequent trapping in the top a-SiNx:H layer. The trapping is reduced when the layer is nitrogen-rich.
Excitation Energy Dependence of Photoinduced Absorption in Intrinsic a-Si:H
Authors: Schultz N. , Vardeny Z.V. , Taylor P.C. 
Published: April 2011

ABSTRACTWe have studied subgap absorption of intrinsic a-Si:H induced by below- and above-gap photo-excitation. We find very similar photoinduced subgap absorption spectra when excited with 2.4 eV or 1.2 eV light. Both spectra exhibit a power-law dependence on laser intensity ΔT ∼ 1a, where a is 0.5 and 0.7 for 2.4 and 1.2 eV excitation energy, respectively. This behavior indicates a change in the recombination mechanism as a function of excitation energy. The PA spectrum excited at 1.2 eV shows a strong dependence on bias illumination. Bias illumination bleaches the absorption according to a power-law as ΔT = c(Ebias)·Iβ, where β is approximately 0.85 and independent of probe energy and bias energy. The parameter c(Ebias) increases superlinearly with bias illumination energy for Ebias > 1.7 eV.
The Intuitive Thermalisation Model Compared to Explicit Multiple Trapping Calculations
Authors: Feist H. , Aichberger S. v. , Kunst M. 
Published: April 2011

ABSTRACTA simple model (the HTMT model) describing the interaction of excess mobile charge carriers with an exponential bandtail is presented. The new model differs from the commonly used intuitive thermalization (TROK) model only by the definition of the demarcation energy. By comparison of the results of the TROK and the HTMT model with numerical calculation of the interaction it is shown that the HTMT model yields an adequate description, whereas the TROK model does not reproduce the absolute values and also has a deviating time dependence at higher temperatures. The origin of these differences is discussed.
Odmr Measurements of Microcrystalline Silicon
Authors: Malten C. , Carius R. , Finger F. , Yamasaki S. 
Published: April 2011

ABSTRACTUndoped microcrystalline silicon films of high crystalline volume fraction were studied by optically detected magnetic resonance (ODMR). Luminescence energies peak at 0.88 eV and emission at 1.3 eV arising from amorphous tissue is negligible. Recombination involving dangling bonds (g=2.0052, g=2.0043) in disordered regions or crystallites and shallow states near the conduction band (g= 1.998) in the crystalline parts of the material are observed. At temperatures below 30 K a very broad feature of approximately 1000 G width is observed, possibly originating from two separate resonances with high g-values of g=2.1 and g=2.08. We suggest the origin to be of hole-states near or in the valence band. No evidence for excitonic recombination was found. Frequency response indicates ODMR lifetimes of all resonances in the range of 10−5s to 10−4s.
Application of Thin-Film Micromachining on Glass
Authors: Boucinha M. , Chu V. , Conde J.P. 
Published: April 2011

ABSTRACTThree dimensional microstructures have been made on glass substrates using surface micromachining techniques. Bridge structures were fabricated using both hydrogenated amorphous silicon and microcrystalline silicon. A low density silicon nitride with an etch rate of 100 Å/s in buffered HF was used as the sacrificial layer. As an example of how micromachining can be applied to large area electronics, thin film transistors (TFT) with the dielectric replaced by an air-gap were fabricated. The electrical characteristics of the first working devices are presented.
Deposition of Highly Conductive n+ Silicon Film for a-Si:H Thin Film Transistor
Authors: Kuo Yue , Latzko K. 
Published: April 2011

ABSTRACTPlasma enhanced chemical vapor deposition of phosphorus-doped n+ silicon film over a wide range of process conditions has been studied. The deposited films were characterized with SIMS, Raman, and XRD. An unusually abrupt change of resistivity over a small SiH4(1% PH3) flow rate has been observed and was correlated to the variation of the film's morphology from amorphous to micrycrystalline. The grains are less than 50 Å in size and has strong <111> orientation. Amorphous silicon thin film transistors with microcrystalline n+ source and drain contacts have consistently good device characteristics. However, the contact resistance is comparable to the channel resistance when the channel length approaches 1 micrometer.
The Influence of Electrons From the Filament on the Material Properties of Hydrogenated Amorphous Silicon Grown by the Hot-Wire Chemical Vapor Deposition Technique
Authors: Nelson Brent P. , Wang Qi , Iwaniczko Eugene , Mahan A.H. , Crandall R.S. 
Published: April 2011

ABSTRACTWe observe that under certain conditions, hydrogenated amorphous silicon grown by the hotwire chemical-vapor deposition technique has dark conductivities varying by several orders of magnitude across the same film. Similarly, the ambipolar diffusion lengths fluctuate significantly in these films, yet there is not much evidence of a corresponding structural change. We attribute this electronic nonuniformity to electrons from the filament reaching insulating substrates and charging the substrate negatively in some regions, thus causing films to grow with inferior material properties in those regions. The effect diminishes with increasing substrate temperature, where the film itself may be conductive enough to remove charge reaching the growing surface. Wellgrounded, conducting substrates seem to be immune from this effect. We reduce this effect by putting a conductive grid on insulating substrates, of close enough spacing to remove the charge, and measure the material properties of the film grown between the conductive elements of the grid.
New Excimer Laser Crystallization in the Lattice Shape to Improve the Uniformity of Electrical Characteristics of Poly-Si TFT
Authors: Jeon Jae-Hong , Park Cheol-Min , Park Kee-Chan , Lee Min-Cheol , Han Min-Koo 
Published: April 2011

AbstarctThe new laser annealing technique to control the surface morphology and microstructure of poly-Si film is proposed. Compared with the conventional laser annealing technique where the laser beam is irradiated on the whole area of active layer, our new method make the laser beam transmitted locally onto the active amorphous silicon (a-Si) layer. Using the masking window in grid shape, the active layer is recrystallized in the lattice shape during the laser irradiation. By the optical microscope and scanning electron microscopy (SEM), we observed the orderly pattern, which consists of amorphous and poly-Si regions. In our new poly-Si film, the rough surface morphology, which is shown in conventional sample, could not be found. Furthermore we fabricated a poly-Si TFT utilizing the active poly-Si film recrystallized by our new method. The new poly-Si TFT showed much higher ON current than the conventional poly-Si TFT, although the leakage current is relatively high. The excellent ON characteristics may be attributed to the uniform surface morphology. After hydrogenation, the electrical characteristics of our new polySi TFT was improved considerably and this device may be applied successfully to the active matrix liquid crystal displays (AMLCD's).
Thin-Film Transistors Fabricated With Poly-Si Films Crystallized by Microwave Annealing
Authors: Choi YongWoo , Lee JeongNo , Jang TaeWoong , Ahn ByungTae 
Published: April 2011

AbstractSolid phase crystallization has the advantages of low cost and excellent uniformity but the crystallization temperature is too high to use glass as a substrate. Using microwave annealing, we crystallized a-Si films at 550 °C within 3 h, which is much shorter than the annealing time at 600 °C of furnace annealing. We fabricated TFTs with poly-Si films crystallized by microwave annealing at low temperature and obtained the characteristics slightly better than or at least comparable to the TFTs by furnace annealing in spite of smaller grain size. This may be due to the improvement of surface roughness of poly-Si film. The poly-Si TFTs with PECVD a-Si film showed better characteristics than the TFTs with LPCVD a-Si film because of larger grain size and smoother Si/SiO2 interface.
Low-Temperature Formation of SiNx Gate Insulator for Thin-Film Transistor Using CAT-CVD Method
Authors: Izumi A. , Ichise T. , Matsumura H. 
Published: April 2011

AbstractSilicon nitride films prepared by low temperatures are widely applicable as gate insulator films of thin film transistors of liquid crystal displays. In this work, silicon nitride films are formed around 300 °C by deposition and direct nitridation methods in a catalytic chemical vapor deposition system. The properties of the silicon nitride films are investigated. It is found that, 1) the breakdown electric field is over 9MV/cm, 2) the surface state density is about 1011cm−2eV−1 are observed in the deposition films. These result shows the usefulness of the catalytic chemical vapor deposition silicon nitride films as gate insulator material for thin film transistors.
Role of RF Power and Gas Mixture in Some Optical and Photoluminescence Properties of Dual-Plasma a-C:H Films
Authors: Heitz T. , Godet C. , Bouree J.E. , Drevillon B. , Chu V. , Conde J.P. , Clerc C. 
Published: April 2011

AbstractElectronic properties of polymer-like hydrogenated amorphous carbon films, grown in a RF-assisted microwave plasma reactor, have been studied using optical absorption and photoluminescence spectroscopies. Using a Forouhi-Bloomer parametrization of π-π* transitions, two regimes are evidenced for increasing C atom density : a decrease of the optical gap Eππ* at constant (H/H+C) content attributed to sp2C clustering, followed by some H elimination with minor changes in Eππ* due to cross-linking of polymer chains. The photoluminescence efficiency in the visible range (peak at ≈ 2.3 eV) is found to decrease over four orders of magnitude at the onset of the cross-linking regime. This quenching is attributed to stress-induced non-radiative centers.
All Printed Bistable Reflective Displays: Printable Electrophoretic Ink and All Printed Metal-Insulator-Metal Diodes
Authors: Park Jaeyong , Jacobson Joseph M. 
Published: April 2011

AbstractWe have printed Metal-Insulator-Metal Diodes onto flexible substrates using hybrid polymer and metal-metal oxide inks. Successful device structures were printed by means of several processes including 1] a two step process of Ta in polymer matrix with thermally grown oxide followed by printed Cr in polymer and 2] a one step process of pre-oxidized Ta microparticles in polymer. Back-to-back diode I-V characteristics were demonstrated with tunable turn-on voltages between 5V and 100V. Coupled with a fully printable bistable, electronically addressable electrophoretic ink which we have developed, such systems open the way for all printed, reflective, bistable electronic displays.
Effects of Ultraviolet-Light on Polyimide Films for Liquid Crystal Alignment
Authors: Gong Shaoqin , Kanicki Jerzy , Ma Lan , Zhong John Z. Z. 
Published: April 2011

AbstractUV-light effects on the polyimide films have been studied by characterizing the film property changes and by measuring the liquid crystal pretilt angle. Infrared, UV-visible and X-ray photoelectron spectroscopy measurements indicate that bond-breaking and oxidation occur during broadband UV-illumination of the film in the air. Free radicals are formed during UV-illumination as evidenced by the analysis of electron spin resonance spectra. Surface tension and polarity are increased after UV-illumination based on the contact angle measurements. While the pretilt angle on the rubbed polyimide film is decreased after nonpolarized UV-illumination, polarized UV-light generates a relatively small pretilt angle on a nonrubbed surface.
Structure of Ions in Liquid-Crystalline Materials
Authors: Naemura Shohei , Nakazono Yuji , Nishikawa Kenichi , Sawada Atsushi , Kirsch Peer , Bremer Matthias , Tarumi Kazuaki 
Published: April 2011

AbstractBoth steady-state current and dielectric-loss measurements were performed on a liquid-crystalline material, 4-(trans-4-pentylcyclohexyl)benzonitryl, in an isotropic liquid phase, which provide information on generation and behavior of ions, dominating DC and AC conductivity, respectively. The frequency dependence measurements of dielectric-loss can successfully estimate such characteristics of ions as total quantity of electricity, diffusion constant (mobility), and the size. With help of chemical analysis like ion chromatography and semi-empirical quantum chemical computation, the majority of ions, especially dominating AC conductivity, were estimated to be inorganic cations with Stokes' radius of around 2 × 10−8(cm), either naked or hydrated, and solvated ions with Stokes' radius of around 5 × 10−8(cm), most probably with the liquid-crystalline molecules at the solvation number of 1.2 in average. The present microscopic investigation of conduction mechanism is of great help for development of liquid-crystalline materials, especially for use in sophisticated displays with excellent picture quality.
Electroluminescent Displays
Authors: King Christopher N. 
Published: April 2011

AbstractThis paper will review the electrical and optical properties of both monochrome and color electroluminescent (EL) displays. A simple electrical model for thin film electroluminescent (TFEL) device operation will be presented and used to describe the luminance and power consumption of TFEL devices. The basic material characteristics desirable for EL phosphors will be described. Progress in the development of monochrome and color EL displays will be presented including TFEL and Active Matrix EL devices and phosphors.
Stepped Gate Polysilicon Thin-Film Transistor for Large Area Power Applications
Authors: Aschenbeck J. , Chen Y. , Clough F. , Xu Y. Z. , Sankara Narayanan E. M. , Milne W. I. 
Published: April 2011

AbstractFor the first time, we report a new poly-Si stepped gate Thin Film Transistor (SG TFT) on glass. The Density of States extracted from measured I-V characteristics has been used to evaluate the device performance with a two dimensional device simulator. The results show that the three-terminal SG TFT device has a switching speed comparable to a low voltage structure and the high on-current capability of a metal field plate (MFP) TFT and the potential for comparable breakdown characteristics.