bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure-Property Relationships in Semiconductor Alloys
Authors: Sher A. , Berding M. A. , Krishnamurthy S. , Van Schilfgaarde M. , Chen A.-B. , Chen W. 
Published: March 2011

ABSTRACTWe have demonstrated that the atomic distribution of constituents in semiconductor alloys is never truly random. There are always interactions causing correlations; the degree and nature of the correlations depend on which interactions dominate and on the growth conditions. While we have identified most of the interactions which are expected to cause correlations, not all of them have been treated completely to date. Therefore, some details remain unclear, but the principal effects can now be appreciated in broad terms.
Orientation Relationships between BCC Deposits and FCC Substrates
Authors: Smith David A. , Segmüller Armin , Taranko A. R. 
Published: March 2011

ABSTRACTOriented deposits are commonplace in vapor deposited films. The origins of this behavior are not always clear. Various bcc metals (Fe, Nb, Mo, Ta, Cr) have been deposited onto single crystal fcc substrates (Au, Ni, MgO, Si, NaCI) which were selected with the intention of varying the character of the substrate-deposit interaction. The resulting structures have been characterized by transmission electron microscopy and grazing incidence x-ray diffraction. The observed variants of the cube-cube and Nishiyama-Wassermann orientation relationship can be understood in terms of minimization of misfit except when there is a weak interaction between substrate and deposit.
Photoemission Study of the α-Sn/Cdte(110) Interface Growth
Authors: Tang Ming , Niles David W. , Hernández-Calderón Isaac , Hóchst Hartmut 
Published: March 2011

ABSTRACTAngular Resolved Photoemission Spectroscopy with Synchrotron radiation has been used to study the MBE growth of α-Sn on CdTe(110). Sn grows epitaxially and the Fermi level pins at 0.72eV above the CdTe valence band maximum. Outdiffusion or segregation of Cd in the α-Sn layer is not observed. For small Sn coverages the Sn4d core spectra show a second component which may be due to the initial interfacial growth of SnTe.
Structural Analysis and Electronic Properties of in on Si(100) from Synchrotron Photoemission Studies
Authors: Rich D. H. , Samsavar A. , Miller T. , Lin H. F. , Chiang T. -C. 
Published: March 2011

ABSTRACTHigh-resolution photoemission spectroscopy was used to study the initial growth and interaction of In on Si(100). A quantification of the number of Si surface atoms selectively modified in the presence of an In adatom is enabled by decomposing the Si 2p core level into bulk and surface-shifted components; this analysis leads to an In-Si bonding coordination number determination. The In-to-Si bonding coordination number is 3 for very low In coverages and decreases to 2 for one half monolayer coverage. An analysis of the In 4d core levels indicates that the In adatoms occupy equivalent sites for the first 0.5 monolayers. Surface state emission near the top of the valence band persists for coverages exhibiting no Si 2p surface core level shift; implications regarding the different mechanisms I ehind the surface state and surface core level shift are addressed. The results are consistent with a structural model deduced from electron diffraction, Auger, and scanning electron microscopy studies.
Epitaxy, Oxidation and Surface Structure of Copper on Gold Films by High Resolution Electron Microscopy
Authors: Krakow William , Cast˜no Victor 
Published: March 2011

ABSTRACTHigh resolution electron microscope studies were undertaken of the epitaxy and oxidation of thin layers (<30Å) of vapor deposited Cu on single crystal Au films. The metal/metal and oxide/metal orientation relationships were analyzed for both the diffraction and imaging modes, before and after the Cu oxidation was significant. For the oxide overlayers two cases were studied: (111) Cu which transforms into three (110) variants of Cu2O, each rotated by 120° and (110) Cu transforming to a layered (211) oxide overgrowth. A lateral displacement of the surface top layer of Cu atoms was found for the (110) orientation of Cu2O. The (211) orientation of Cu2O had two structural variants of surface ordering rotated by 90° relative to the underlying metal. One of these cases directly exhibits a 3.01Å × 7.39Å supercell structure characteristic of a 0.58Å atomic step height of the (211) planar layers perpendicular to the surface.
Nucleation and Growth Processes in OMCVD of GaAs
Authors: Shastry S. K. , Hefter J. 
Published: March 2011

ABSTRACTThe initial stages of GaAs growth on mirror-polished metal (W, Mo), semiconductor (Si, GaAs), and insulator (alumina) substrates have been experimentally studied in the organometallic chemical vapor deposition (OMCVD) process. Growth on the metallic substrates is often polycrystalline and nonepitaxial, while epitaxial GaAs layers with preferred orientations can be grown relatively easily on the nonmetallic substrates. The rate of nucleation of GaAs on all the substrates is found to increase with increasing arsine flow rate and with decreasing growth temperature. Our experimental results suggest that the GaAs nucleation process on all the substrates consists of an initial condensation and nucleation of gallium and subsequent formation of GaAs by arsenic supersaturation. In addition, following the nucleation of GaAs, a decrease in the substrate temperature is observed until further GaAs nucleation occurs, suggesting continued supersaturation. The nonepitaxial growth on the metallic substrates is attributed to the high rate of GaAs nucleation on these substrates.
Effects of Dopants on the Nucleation and Growth of NiSi2 on Silicon
Authors: Lu S. W. , Nieh C. W. , Chu J. J. , Chen L. J. 
Published: March 2011

ABSTRACTThe influences of implantation impurities, including BF2, B, F, As and P on the formation of epitaxial NiSi2 in nickel thin films on ion-implanted silicon have been investigated by transmission electron microscopy.The presence of BF2, B, and F atoms was observed to promote the epitaxial growth of NiSi2 at low temperatures. Little or no effect on the formation of NiSi2 was found in samples implanted with As or P ions.The results indicated that the influences of the implantation impurities are not likely to be electronic in origin. Good correlation, on the other hand, was found between the atomic size factor and resulting stress and NiSi2 epitaxy at low temperatures.
The Early Stages of the Spinel-Alumina Phase Transformation
Authors: Simpson Y. Kouh , Carter C. B. 
Published: March 2011

ABSTRACTThe initial stage of topotactic growth of Ni-Al spinel into Al2O3has been examined using transmission electron microscopy. A new experimental approach to the study of solid-state reactions, which may be adapted for in-situ experiments for low-temperature systems, has been used in this study. In its present form, the technique involves heating a thin film of one oxide in the presence of a vapor of the second oxide. In the study of the growth characteristics of Ni-Al spinel phase, the orientation of the Al2O3substrate has been found to influence greatly both the structural and morphological aspects of the spinel growth. In particular, the topotactic relationship between the spinel and the alumina are very different for (0001) and {1120} substrate orientations. The very early stage of the kinetics of the spinel growth, in which the length and the width of the spinel particles are only a few hundred angstroms, is illustrated with the results obtained from the re-heating experiments. The structure of the spinel-alumina interface has also been studied using high-resolution electron microscopy. These results are discussed in relation to the different models proposed for the spinel-alumina phase transformation.
Initial Stages of Interface Formation: The Influence of Surface Reconstruction
Authors: Gossmann H.-J. 
Published: March 2011

ABSTRACTThe initial stages of interface formation are crucial for the growth of an overlayer, particularly for ultra-thin films. While growth rate, growth temperature and lattice match are important parameters in molecular beam epitaxy, growth of semiconductor heterostructures always begins on a reconstructed surface. The effect of this reconstruction has to be known before a complete understanding of the growth process is possible. Two examples will be discussed: (1) A necessary condition for perfect growth is the reordering of the substrate surface, i.e. those atoms at the interface which are originally displaced due to the reconstruction have to be brought back to bulk positions. Si(111)7×7 and Si(100)2×1 surfaces behave differently in this respect. The 2×1 orders upon deposition of Si, Ge or Sn at room-temperature whereas the 7×7 does not. This result will be correlated with the different classes of reconstruction to which these surfaces belong. The possible rela-tionship with the difference in substrate temperatures required to achieve homo-epitaxial growth on Si(100) and Si(111) surfaces will be discussed. (2) Perfect growth also relies on proper control of the growth-mode. As an example, the island-ing behavior found for deposition of Sn on Si will be discussed. While surface diffusion over macroscopic distances is observed, dramatic changes in the affinity for clustering occur depending on surface reconstruction and preparation, suggesting that clustering in this system may be controlled by appropriate choices of growth parameters.
Drift Mobility Measurements Under Single and Double Injection in a-Si:H
Authors: Xu L. , Winborne G. , Silver M. , Cannella V 
Published: March 2011

AbstractDrift mobility measurements under high level double injection in p/i/n and single injection in M/i/n devices have been made as a function of d.c. voltage and temperature using a small step voltage technique. For comparable ratio's of V/L2 the transit time of injected electrons was of order one decade shorter under double injection than under single injection. The room temperature drift mobility for single injection was approximately 1cm2−1s−1. We attribute the difference in drift transit time to a higher extended state mobility with double injection than with single injection due to the neutralization of charged defects.
Hydrogen Diffusion and Thermal Equilibrium of Electronic States in a-Si:H
Authors: Street R. A. 
Published: March 2011

AbstractThis paper reviews the recent evidence for thermal equilibrium effects in the electronic behavior of hydrogenated amorphous silicon, and relates the thermally induced changes to the motion of bonded hydrogen. The electronic properties are studied through measurements of d.c conductivity and-.weep out, and the role of hydrogen is explored through its diffusion. The magnitude and doping dependence of the diffusion coefficient DH matches the data on the equilibration of the electronic states. Furthermore both the diffusibn and the relaxation can be described by the same dispersive time dependence. It is argued that the diffusion of hydrogen is the rate limiting step in the the equilibration mechanisms and determines the kinetics.
Hydrogen Microstructure in Amorphous Semiconductors.
Authors: Gleason Karen K. , Petrich Mark A. , Reimer Jeffrey A. 
Published: March 2011

AbstractThe effects of deposition parameters on the H microstructure of plasma deposited amorphous silicon (a-Si:H) and amorphous silicon carbide (a-SiC:H) are measured via multiple quantum nuclear magnetic resonance (MQ NMR). These studies indicate clusters of 5 to 7H atoms exist in a-Si:H films prepared at temperatures ranging from 113 to 324°C. In the range from 270 to 324°C, only these small clusters exist, but lower temperature films also contain larger clusters. Annealing studies indicate H rearranges in a-Si:H prior to evolution. Deposition temperature and annealing temperature have similar effects on H concentration in a-Si:H, but deposition temperature control the density and microstructure of the film. The addition of dopant atoms also affects the H microstructure, with phosphorous causing larger H clusters to form, and boron reducing clustering in a-Si:H films. This perturbation of the film's microstructure suggests that the effects of dopant addition are more complex in amorphous than in crystalline semiconductors. The concentration of carbon atoms also effects H microstructure of a-SiC:H in a complex way. We surmise that H microstructure, rather than H content, determines amorphous semiconductors properties.
A Structural Analysis of Thin Amorphous Silicon Films
Authors: Erkoç Ş. , Halicioglu T. , Tiller W. A. 
Published: March 2011

AbstractUsing a semiempirical potential energy function for Si, thin amorphous films of Si have been simulated on crystalline Si by a partial melting and subsequent quenching process. After relaxation at 450°K, the dominant structural feature was a dense free surface skin with a void layer underneath for both c-Si(100) and c-Si(111) substrates and for film thicknesses up to 16Å. Tetrahedral coordination was maintained throughout the amorphous region and structural differences were noted in the α-Si/c-Si interface region for the two orientations considered.
Film Growth Mechanisms of Amorphous Silicon in Diode and Triode Glow Discharge Systems
Authors: Tsai C. C. , Shaw J. G. , WACKER B. , Knights J. C. 
Published: March 2011

AbstractBy simulating the growth morphology of plasma-deposited amorphous silicon films on patterned substrates using a Monte-Carlo technique, we find the effective sticking coefficient for the dominating mass transporting species to be quite different depending on the film growth mechanism. The physical-vapor-deposition-like growth regime producing defective materials is associated with species like SiH2 and SiH which have a large effective sticking coefficient, while the chemical-vapor-deposition-like process producing “device quality” materials is linked to species like SiH3 which has a much smaller effective sticking coefficient. In a triode reactor the physical-vapor-deposition-like process is suppressed since species with small effective sticking coefficients are selected. However, the growth rate decreases rapidly as the substrates are moved away from the plasma. There seems to be an incompatibility between good material quality and fast growth rate in the plasma deposition of amorphous silicon in either diode or triode reactors.
The Role of Lattice Relaxation in the Competition Between Optical and Thermal Transitions from Gap States in Hydroacenated Amorphous Silicon
Authors: Gelatos A. V. , Cohen J. D. , Harbison J. P. 
Published: March 2011

AbstractWe have carried out a detailed study of the competition between optical and thermal transitions from mobility gap states in hydrogenated amorphous silicon films. By employing transient photocapacitance and capacitance DLTS techniques on n-type doped films, we have observed the dangling bond optical transitions:D− → D0 + e and D0 → D+ + e, and the thermal transitions: D− → D0 + e and D0 → D0 + h. From the transition energies we have determined that the degree of lattice relaxation for dangling bonds does not exceed 0.1 eV and that the value Ueff of the D−/D0 splitting is 0.3 ± 0.1 eV. Voltage pulse photocapacitance studies on undoped films revealed the existence of the optical transition D−/D0 + e. In addition, in all films we have observed a photocapacitance signal due to optical transitions from the valence band tail states (over the energy range 1.4 to 1.9 eV) at temperatures as high as 440 K, in spite of the expectation that such shallow photoexcited holes would immediately be thermally emitted yielding no photocapacitance signal. We discuss possible explanations for this result by considering two different trapping models.
Predictions on the Physical Properties of Amorphous Carbon-Tin Semiconducting Alloys: II Photoconductivity Properties
Authors: Mpawenayo Prosper 
Published: March 2011

AbstractIt is intended to throw some high lights on the photoconductivity properties of narrow band semiconducting CSn alloys. The feasability, the structure and the usual optical properties of dielectric constants and optical gap have been predicted in a previous paper /1/. Starting with a number of well acknowledged models for semiconductors, properties, the values of the ratio between the light and the dark conductivities of a material having an o9tifal gap of 1.2 eV at 300 °K, under an illumination of 1016 photons cm−2s−1 are found between 1 and 103, but a density of gap states lower than 1018 cm−3 eV−1 is required.
Why the Photoconductivity Decreases in a-SiC:H and a-SiGe:H when the Amount of Alloying Increases
Authors: Mahan A. H. , Raboisson P. , Menna P. , Tsut R. 
Published: March 2011

AbstractInfrared, photoconductivity, and photothermal deflection spectroscopy measurements have been used to probe the relationship between material quality and the amount of microstructure in glow discharge deposited a-SiC:H and a-SiGe:T films. We find that the microstructure is directly responsible for the decrease in photoconductivity observed in both alloys as a function of increased alloy content. The microstructure does this by causing a decrease in steepness of the Urbach tail, thus allowing for an increase in both carrier trapping at the wider band edges and carrier recombination at or near the band tails.
Carrier Transport in Compositionally Modulated a-Si:H Based Superlattice Structures
Authors: Wronski C. R. , Persans P. D. , Abeles B. 
Published: March 2011

AbstractResults are presented on the electron transport, parallel and perpendicular to the layers, in a Ge:H/a-Si:H superlattices. The dependence of this carrier transport on the optical gap shifts, the heterojunction band alignment, as well as the bulk properties and thickness of the Ge,Si layers is established. No significant change in the transport mechanisms at the band edge or Ge with dr was detected.
Interface Passivation in Amorphous Silicon TFTs by Various Gate Dielectric Materials
Authors: Fryea R. C. , Wong C. C. , Kornfeld C. 
Published: March 2011

AbstractWe have used photothermal deflection spectroscopy to examine deep gap absorption in amorphous silicon films deposited on silicon oxide and silicon nitride. Variations in the interface state density deduced from PDS correlate well with the performance characteristics of thin-film transistors. We have demonstrated processes which degrade the interfacial abruptness also increase the interface state density. In transistors this leads to a degradation in device stability. We found devices with oxide gates to be more stable and show lower interface state density than devices with nitride gates for a specific set of deposition conditions. The correspondence between deep gap absorption and transistor characteristics shows that PDS is a valuable technique for characterizing and optimizing fabrication processes.
The Influence of Bulk and Interface Gap States on the Performance of Amorphous Silicon Thin Film Transistors
Authors: Bohm M. , Houghton J. , Salamon S. 
Published: March 2011

AbstractAmorphous silicon thin film transistors with on/off ratios >108 and on currents >100 μA for supply voltages <30 V have been manufactured. The transistors are of the structure glass/Cr/SiNx/intrinsic a-Si/n+a-Si/Al. The field effect electron mobility is typically 0.24 cm2 /Vs. Evaluation of quasistatic CV measurements yields a gap state density of 3.2*1016 cm−3eV−1 at midgap. A one-dimensional model calculation describing the influence of bulk and interface gap states and various other material and geometry parameters on transistor performance is outlined. Calculated data include space charge density, spatial distribution of band bending, band bending vs gate source voltage, static capacitance, and channel conductance. A fit calculation for the experimental sub pinch-off transfer characteristic of a thin film transistor is presented.
The Effects of Coordination and Local Disorder on Impurity States in Hydrogenated Amorphous Silicon
Authors: Nichols C. S. , Fong C. Y. 
Published: March 2011

AbstractThe self-consistent pseudopotential method has been used to calculate the electronic structure of a periodic model of hydrogenated amorphous silicon containing, independently, P and B impurities. We have investigated both impurities in threefold- and fourfold-coordinated sites. Both types of sites studied also include the realistic distortion inherent in disordered systems. In fourfold coordination, both P and B introduce gap states, the energy and spatial extent of which depend upon the local geometrical distortion. In threefold coordination, the lone pair state of P is found below the valence band edge, while the B non-bonding state is found above the conduction band edge. The effects of local geometrical distortion on both of these states is also discussed. Comparisons with other calculations and experimental results are made.
An Investigation of Photo-Induced Degradation by Means of Photothermal Deflection Spectroscopy
Authors: Bennett M. S. , Wiedeman S. , Newton J. L. , Rajan K. 
Published: March 2011

AbstractAbsorption measurements of as deposited and photodegraded intrinsic amorphous hydrogenated silicon films were made using photothermal deflection spectroscopy (PDS). The films were light-soaked in situ using HeNe laser light to simulate AM1 illumination. An increase in subbandgap absorption occurred predominantly near energies of 1.2eV. A simple model was developed in which a density of states function is hypothesized and the resulting optical absorption at subgap energies is calculated. The measured absorption could be well matched in all cases by assuming a single peak of defect states at or slightly below the Fermi level. Further, the observed changes in optical absorption due to degradation could be modeled by increasing the density of the single peak of defect states and moving the Fermi level towards the valence band.
Amorphous Silicon-Carbide Multilayered Visible-Light Emitting Diode
Authors: Kruangam Dusit , Deguchi Masahiro , Hattori Yutaka , Toyama Toshihiko , Okamoto Hiroaki , Hamakawa Yoshihiro 
Published: March 2011

AbstractA series of systematic trials to improve the light emission efficiency has been made on thin film visible a-SiC LEDs. A wide variety of the approaches, such as a superlattice structure, p-i-n/p-i-n tandem structure, an efficient injection electrode with a wide-gap layer etc., have been done. From the results, two practically available new technologies for bright LEDs have been developed, that is; a) a hot carrier injection structure by inserting a highly- resistive layer between p-and i- or i- and n-layers and b) a wide-gap highly-conductive p-type injector layer prepared by ECR (Electron Cyclotron Resonance) CVD deposition. With these trials, the brightness of yellow LEDs have been increased by more than one order of magnitude to be about 5cd/m2