bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and Properties of Inversion Domain Boundaries in β-Sic
Authors: Lambrecht W. R. L. , Lee C. H. , Segall B.
Published: March 2011

The structure of inversion domain boundaries in β-SiC (i.e. boundaries between domains with inverted Si and C positions) is investigated by means of a Keating model. For the (110) boundary, the relaxation of the C-C and Si-Si bonds towards the ideal bond lengths which occur in the diamond structure can basically be achieved by a rotation of neighboring Si-C bonds. For the (001) boundary, it is achieved by varying the spacing between the domains. The electronic properties and total energy of formation of the relaxed (110) boundary are studied by means of linear muffin-tin orbital calculations. The interface localized states in the semiconducting gap are mainly due to the Si-Si bonds and lead to a semimetallic situation near the interface.
The Application of Glancing Angle Exafs to Study the Structure of Platinum-Nickel Multilayers
Authors: Lamble G.M. , Heald S.M. , Clemens B.M.
Published: March 2011

Recent reports have correlated the mechanical properties of multilayers with a structural expansion of the constituents. Whether this expansion is an interface or bulk effect remains in dispute. We apply the technique of glancing angle EXAFS to obtain information about the local structure and multilayer composition and use these results to shed light on certain aspects of this controversy. The experiments were performed on platinum-nickel multilayers of varying bilayer thickness. Measurements were made by fluorescence detection of EXAFS beyond both the Pt LIII and the Ni K edges. Considerable interlayer mixing is evident, as is the presence of order within the interface. We additionally find that the bulk metallic character is retained within the layers.
Atomic Scale Structure of Twin Boundary In Y-Ba-Cu-O Superconductors
Authors: Zhu Yimei , Suenaga M. , Xu Youwen , Kawasaki M.
Published: March 2011

High resolution electron microscopy of the twin boundary layers in YBa2(Cu1-xMx)3O7–8 for x=0 and 0.02 and M=Zn, Fe and Al showed that the boundary widths are ∼1 nm for the pure and the Zn substituted YBa2Cu3O7, 2.5∼3 nm for the Fe and Al substituted oxide. It was found that the lattice plane is shifted across the twin boundary by (1/3 ∼ 1/2)·2d(110) along the boundary. The broadening of the layer for the cases of Fe and Al is also thought to be associated with a reduction of the twin boundary energy, which also leads to an increased twin density.
Photoemission Characterization of Thin Film Nucleation on Inert Substrates
Authors: Haugstad G. , Raisanen A. , Caprile C. , Yu X. , Franciosi A.
Published: March 2011

Synchrotron radiation photoemission was used to characterize Sm and Mn thin film nucleation and growth on solid Xe substrates, in the 3×1014 - 2×1016 atoms/cm2 coverage range. Film growth is well approximated by a model in which the nucleation site density remains constant and hemi-ellipsoidal particles increase in size until coalescence is achieved. Site density and average cluster size are determined from the coverage-dependence of metal and Xe photoemission intensities. Size estimates are confirmed by experimental fingerprints of coalescence.
The Initial Stages of MBE Growth of InSb on GaAs(100) - A High Misfit Heterointerface
Authors: Kiely C.J. , Rockett A. , Chyi J-I. , Morkoc H.
Published: March 2011

The initial stages of heteroepitaxy of InSb on GaAs(100) grown by MBE have been studied by transmission electron microscopy. Three dimensional InSb island growth occurs in which the majority of the 14.6% misfit strain is accommodated by a square array of a/2<011= edge-type misfit dislocations. The implications of each island having a well defined defect array before coalescence into a continuous epilayer are discussed. Some 600-type a/2<101= interfacial defects and associated threading dislocations are also observed in coalesced films and possible reasons for their existence are explained. A strong asymmetrical distribution of planar defects in the InSb islands is observed and the origin of the asymmetry is discussed. Finally some evidence for local intermixing in the vicinity of the interface is presented.
Large Area Silicon Avalanche Photodiodes: Photomultiplier Tube Alternate
Authors: Reiff G. , Squillante M.R. , Serreze H.B. , Entine G. , Huth Gerald C.
Published: March 2011

Silicon avalanche photodiodes have recently been shown to be a potential replacement for vacuum tube photomultipliers in many nuclear scintillation detector applications. The large active area, low noise, and ease of use of these solid-state photomultipliers makes them ideally suited to scintillation detector applications where overall size and ruggedness are a major concern. Historically, avalanche photodiodes have been limited for use in this capacity by small active areas, low internal gains, and poor optical sensitivity at the wavelengths at which most solid scintillator materials emit. Recent advances as the result of research aimed directly at the solution to these problems however, have successfully demonstrated one inch active area silicon avalanche photodiodes which produce a FWHM resolution of 9.5% for Cs137 at room temperature when coupled to a 1″ × 1″ NaI(Tl) scintillation crystal. Improvements to both material quality and device structure have advanced the state-of-the-art to make silicon avalanche photodiodes a viable alternative in scintillation gamma spectroscopy as well as for large area optical, beta, and low energy x-ray detectors.
Thick Surface Barrier Detectors Made of Ultra-High Purity P-Type Si Single Crystal
Authors: Shiraishi F. , Takami Y. , Hosoe M. , Ohsawa Y. , Sato H.
Published: March 2011

The detector material used in this experimments is Ultra-High Purity p-type Si crystal. The material was single-crystalized through floating zone process from poly-crystal grown by thermal decomposition of highly refined mono-silane gas which had been purified by molecular sieves of specially prepared Zeolite powder.

The resisitivity at room temperature is normally above 30 kΩ.cm, and the value of the highest grade ones exceeds 100kΩ.cm which corresponds to the Boron concentration of 1.5×l011 B/cm3.

The potentiality of this material for detector use was investigated through Surface Barrier Detector fabrication. Detectors of above 4 mm thick and of excellent characteristics both at room temperature and at liq. N2 temperature could readily be fabricated. Owing to tie extremely high resisitivity, detectors can be made either partially depleted or totally depleted simply by properly selecting the wafer resisitivity and the thickness.

In detector fabrication, the proper surface chemical treatment is very important, and seriously affects the leakage current and breakdown characteristics.

Ultra-High Purity Si is promising as new detector material and has good potentiality to replace Si(Li) as followings:

1) simple and easy detector fabrication,

2) potentiality of thick detector fabrication (∼1cm),

3) no precipitation problem of Li ions, and

4) feasibility of thick ⊿E detector with thin entrance window on both faces.
Characterization of Single Crystal Mercuric Iodide (HgI2) Using Thick Detector Structures
Authors: Beyerle A. , Hull K. , Markakis J. , Schnepple W. , Van Den Berg L.
Published: March 2011

Single crystal sections of HgI2 (about 1 cm thick) have been evaluated for charge carrier transport properties. Using these thick detector structures, surface effects produced during fabrication are reduced, enhancing the bulk property characteristics. The standard time-of-flight method was used to determine electron and hole mobilities. Lifetime measurements for electrons and holes were made by direct observation of the carrier decay where crystal transit times were long compared to lifetimes. Nonlinear charge carrier velocities have been observed during mobility measurements. These nonlinearities impair a partial charge collection technique [1,2,3] for spectra generation taken with thick detectors while having a lesser effect on the standard full charge collection approach. Partial charge collection methods have produced greater peak efficiencies than full charge collection, and investigations of crystal properties are being used to enhance this method.
State-of-the-Art X-Ray Detectors Fabricated on PCG Grown Mercuric Iodide Platelets.
Authors: Squillante M. R. , Lis S. , Hazlett T. , Entine G.
Published: March 2011

Recent developments on HgI2 detectors fabricated from platelets grown by the Polymer Controller Growth (PCG) technique have resulted in a better understanding of this remarkable process and provide increased hope for the future of room temperature operable, high resolution x-ray detectors. The benefits of PCG are higher purity using reagent grade materials, better control of stoichiometry, rapid growth, and simplified fabrication. This latter benefit is even more significant when the extreme fragility of HgI2 crystals is considered. The problems of device resolution crystal stability and uniformity, and control ot platelet growth were investigated under a NASA funded program. HgI2 devices fabricated from PCG platelets gave room temperature energy resolutions under 400 eV (FWHM) for the 5.9 eV Mn x-ray. Models for the polymer assisted transport are discussed along with an analysis of spectra obtained from PCG grown devices. Reproducibility has been demonstrated both for platelet growth and device performance.
Ohmic and Rectifying Contacts on High Resistivity P-Type Cadmium Telluride
Authors: Musa A. , Ponpon J.P. , Hage-Ali M.
Published: March 2011

Ohmic and rectifying contacts on high resistivity etched P-type cadmium telluride have been studied in order to produce diode structures.For this,we have first investigated the properties of gold contacts obtained by chemical reactions of CdTe dippedin gold chloride.Both electrical characterization and structure have been analyzed as a function of the experimental conditions of the contact deposition.The results can be interpreted in terms of a current flow enhanced by tunnelling through the Au-CdTe junction and related to the structure of the interface a few tens of nanometer below the gold contact. In addition,several rectifying contacts have been investigated , in order to achieve a structure having low leakage current.
Growth of Thin Nickel Silicide Layers on Clean B-Doped Si(111) Surfaces at Room Temperature
Authors: Luo L. , Smith G. A. , Gibson W. M.
Published: March 2011

The initial growth stages of Ni on clean B-doped Si(111) were studied at room temperature using high energy Ion channeling and Monte Carlo computer simulations of the Ni/Si interface. The results suggest that the first monolayer of Ni atoms diffuse to reaction sites in the fourth layer of the Si(111) substrate where nickel suicide growth begins. Further Ni deposition (up to ~ 3 ML) leads to the growth of NiSi2 which is thought to be a diffusion barrier that terminates further formation of NiSi2 at room temperature.
Preferential Growth of CoSi2 in Co/Si Solid State Interaction by Rapid Thermal Annealing
Authors: Liu Ping , Hong Feng , Li Bing-Zong , Sheng Xiao-Liang
Published: March 2011

The CoSi2 thin film growth by Co/Si solid state interaction was investigated. The electrical and crystal properties of the films formed on (111) and (100) Si substrates were characterized after a rapid thermal annealing. A strong preferential CoSi2 (111) orientation grain growth was observed on (111)Si substrate. The formed CoSi2 film was highly conductive with a resistivity of 15.5 µΩ · cm.
Silicide Formation and Thermal Stability of Ni/Si/GaAs Interface
Authors: Yamamoto Y. , Ishibashi K. , Suzuki S. , Shim T.E.
Published: March 2011

The suicide formation and thermal stability of the Ni/Si/GaAs structures have been investigated. Vacuum deposited Ni and Si onto a (100) GaAs were annealed at temperatures between 500 °C and 650 °C. In the case that the relative amount of Ni and Si was unity, a stoichiometric NiSi was formed and silicide/GaAs interface was quite stable. The Stoichiometric NiSi did not decompose into NiSi2 and Ni at a temperature of 650 °C. When Ni was in excess in amount for the formation of stoichiometric nickel suicides, free Ni atoms were generated, resulting in unstable interfaces.
Ordered Ternary Alloys by Atomic Layer Epitaxy
Authors: Mcdermott B.T. , Reid K.G. , Dip A. , El-Masry N.A. , Bed Air S.M. , Duncan W. , Yin X. , Pollak F.H.
Published: March 2011

We report on the successful growth of GalnP on GaAs substrate by Atomic Layer Epitaxy using organometallic and hydride sources. Growth was achieved by sequential exposure of the substrate to TMGa, PH3, TEIn and PH3. X-ray diffraction showed compositional lattice-matching optimally at 550°C with arbitrary choices of the mole fractions of the precursors in the gas phase. TEM also confirmed the highest ordering at this growth temperature on (100) substrates. Uniformity was excellent using Atomic Layer Epitaxy. Growth on (111)A GaAs substrates produced no evidence of the ordered CuPt phase present on (100) substrates.
Dislocation Density Reduction in GaAs Epilayers on Si Using Strained Layer Superlattices
Authors: Sharan S. , Narayan J. , Fan J. C. C.
Published: March 2011

Defects such as dislocations and interfaces play a crucial role in the performance of heterostracture devices. The full potential of GaAs on Si heterostructures can only be realized by controlling the defect density. The reduction of threading dislocations by the use of strained layer superlattices has been studied in these heterostructures. Several superlattice structures have been used to reduce the density of threading dislocations in the GaAs epilayer. The use of strained layer superlattices in conjunction with rapid thermal annealing was most effective in reducing threading dislocation density. Transmission electron microscopy has been used to study the dislocation density reduction and the interaction of threading dislocations with the strained layers. A model has been developed based on energy considerations to determine the critical thickness required for the bending of threading dislocations.
A Tem Investigation of the Initial Stages of InSb Growth on GaAs (001) by Molecular Beam Epitaxy
Authors: Zhang X. , Staton-Bevan A.E. , Pashley D.W.
Published: March 2011

This investigation focuses attention on the very early stages of MBE growth of InSb on GaAs (001). Both conventional and high resolution TEM have been used for a study of InSb layers varying between 5 and 300 monolayers in average thickness. The observations provide conclusive evidence of 3D nucleation and island growth. Complete lattice relaxation is brought about by a network of 1/2 <110> Lomer dislocations at the InSb/GaAs interface and there is strong evidence for the presence of an additional sphalerite interfacial phase. Threading dislocations and planar defects in the InSb epilayer are mainly introduced during island coalescence.
Heteroepitaxial Growth of InP on GaAs with Interface Layer Grown by Flow-Rate Modulation Epitaxy
Authors: Chen W. K. , Chen J. F. , Chen J. C. , Kim H.M. , Anthony L. , Wie C. R. , Liu P. L.
Published: March 2011

We have grown and characterized heteroepitaxial films of InP on GaAs. We demonstrate that by using flow-rate modulation epitaxy to grow the interface layer in a two-step process, we can improve the quality of heteroepitaxy films. The full-widths-at-half-maximum of the x-ray rocking curve and the 10-K photoluminescence spectrum for a 6.2-μm-thick InP/GaAs are 144 arcsec and 1.28 meV, respectively.
Metalorganic Chemical Vapor Deposition of InP by Pulsing Precursors
Authors: Chen W. K. , Chen J. C. , Anthony L. , Liu P. L.
Published: March 2011

We have grown InP by supplying precursors alternately into the reactor of a metalorganic chemical vapor deposition system. Epitaxial growth has been obtained with a substrate temperature as low as 330 °C. The growth process is mass-transport-limited in the temperature range of 420 to 580 °C. It is kinetic-controlled below 400 °C. At 340 °C, we have achieved monolayer growth in each cycle, i.e., atomic layer epitaxy.
Determination of 3-Dimensional Defect Structures in Gallium Arsenide Epilayers on Silicon Using White Beam Synchrotron Radiation Topography in both Transmission and Grazing Bragg-Laue Geometry.
Authors: Dudley M. , Yao G.-D. , Wu J. , Liu H.-Y. , Kao Y.C.
Published: March 2011

White beam synchrotron topography in both transmission and grazing Bragg-Laue geometries has been used to reveal the 3-dimensional defect structure in MBE grown GaAs epilayers on Si. Defects observed and characterized include substrate threading dislocations and interfacial dislocations. Dislocation line direction and Burgers vector analysis was performed on transmission topographs. The relationship between substrate threading dislocations and interfacial dislocations was established. In the grazing Bragg-Laue case, manipulation of geometry enabled depth profiling of defect structures in the epilayer. The position of the interfacial dislocations was verified by correlating penetration depth analysis with the visibility of the dislocations under different diffraction conditions.

This technique affords a rapid and non-destructive way of quantitatively characterizing processing induced damage in such systems.
Selective Area Growth of GaAs on Si by Electron-Cyclotron-Resonance Plasma-Excited Molecular-Beam-Epitaxy (ECR-MBE)
Authors: Shibata Tomohiro , Kondo Naoto , Nanishi Yasushi , Fujimoto Masatomo
Published: March 2011

Successful selective area growth of GaAs on Si following low-temperature plasma cleaning of the Si surface is carried out by ECR plasma-excited MBE. Both cleaning and selective area growth are carried out at 630° C. GaAs selectively grows only in Si windows patterned in the SiN mask. Neither deposition on the SiN mask nor anomalous growth at the mask edge is observed. GaAs thickness is independent of the SiN mask width, which implies that the plasma-enhanced desorption of migrating atoms from the SiN mask is essential in this selective area growth. Furthermore, results for the helium-diluted arsine imply that the plasma-enhanced desorption is mainly caused by physical bombardment.
Raman Study of MOMBE and Plasma-MOVPE Grown III-V Layers on Si(100).
Authors: Geurts J. , Finders J. , Münder H. , Kamp M. , Oehlers M. , Loth H. , Musolf J. , Leiber J. , Brauers A. , Weyers M. , Balk P.
Published: March 2011

The crystalline quality of the transition region between buffer layer and epilayer in MOMBE (metalorganic molecular beam epitaxy) and plasma-MOVPE (metalorganic vapour phase epitaxy) grown GaAs layers on Si(100) is analysed by Raman scattering with variation of the penetration depth and besides bevel polishing or step etching. The region with considerable lattice imperfections is essentially confined to the original buffer layer.
The Nucleation and Growth of Germanium on (1102) Sapphire Deposited by Molecular Beam Epitaxy
Authors: Godbey David J. , Twigg Mark E.
Published: March 2011

Single crystal undoped germanium has been grown successfully for the first time on (1102) sapphire [1,2]. Germanium was found to grow (110) with an in plane registry of Ge(111)/Al203(1012) [1]. When a 2μm germanium film was grown on (1102) sapphire at 800°C and after a substrate preanneal of 1400°C, the X-ray line width of the Ge(220) reflection was measured to be 230 arcseconds [2]. Strain was observed only in germanium films that were thinner than 40 nm [2].
Magnetic Properties of Al/Tb-Fe-Co Multilayer Thin Films
Authors: Barnard J.A. , Yan B.D. , Kim M.H. , Warren G.W.
Published: March 2011

A series of periodic multilayer Al/Tb-Fe-Co thin films have been prepared by dc-magnetron sputtering. The films are of the form (xA/yB)n, where x and y are the thicknesses of the A and B layers respectively, and n is the number of bilayer units. Individual layers are from 2-40nm thick. The magnetic properties of the films have been measured as a function of Al and Tb-Fe-Co layer thicknesses by vibrating sample magnetometry (VSM). An homogeneous film of the Tb-Fe-Co alloy was grown under identical conditions and found to have in-plane easy magnetization. Pronounced interfacial and/or reduced dimension effects have been found in the multilayer systems. These include evidence for a “dead layer” in the interface regions (~2nm thick) and reversal of the direction of easy magnetization from in-plane (in the homogeneous thin film samples) to strongly perpendicular in the multilayer configuration.
Time Resolved Measurements of Radiative Recombination in GaAs/AIGaAs Heterostructures
Authors: Bergman J.P. , Zhao Q.X. , Holtz P.-O. , Monemar B. , Sundaram M. , Merz J.L. , Gossard A.C.
Published: March 2011

The radiative recombination of two-dimensional (2D) carriers in an n-channel GaAs/AIGaAs heterojunction has been studied with time resolved photoluminescence (PL). Two bands related to the recombination of 2D carriers, the so called H-band 1 (HB1) and H-band 2 (HB2), are observed in PL. The spectral shape and position is strongly dependent on the sample and the experimental conditions. The H-bands are e.g. found to shift within a large energy range with the excitation intensity. We report here on the dependence of the decay times of the H-bands on their spectral position. The results are consistent with a recombination process involving 2D electrons, confined in the interface notch, and three-dimensional (3D) holes either from the valence band (HB1) or from neutral acceptors (HB2) in the active GaAs layer. The decay times of HB1 are found to vary in the range of 2-100 ns, while the corresponding decay times of HB2 are in the range of 100 ns - 10 µs.
Dislocation Behaviour in GexSi1-x Epilayers on (001)Si
Authors: Kvam Eric P. , Maher D.M. , Humphreys C.J.
Published: March 2011

We have observed that the nature of misfit dislocations introduced near the critical thickness in GexSi1-x alloys on (001)Si changes markedly in the region 0.4 ≤ x ≤ 0.5. At or below the lower end of this compositional range, the observed microstructure is comprised almost entirely of 60° type dislocations, while at the high end, the dislocation structure is almost entirely Lomer edge type. Concurrent with this change, the dislocation density at the top of the epilayer varies by a factor of about 60X. Similarly, several other observables (e.g. dislocation length and spacing) also change appreciably.

Part of the reason for the morphological variation seems to be a change in the source for dislocation introduction, in conjunction with a change in glide behaviour of dislocations as a function of film thickness. Evidence will be presented that indicates strain, as well as thickness, has a critical value for some dislocation introduction mechanisms, and that these together determine the resulting microstructure.

Furthermore, it appears unlikely that the edge-type Lomer dislocations which appear at about x = 0.5 are either introduced directly, by climb, or grown in, as in the three-dimensional island growth and coalescence which occurs when x approaches unity. Instead, a two-step mechanism involving glissile dislocations is proposed and discussed.
Spatially Indirect Optical Transitions in Semiconductor Multiple Quantum Wires
Authors: Weiner J. S. , Danan G. , Pinczuk A. , Valladares J. , Pfeiffer L. N. , West K.
Published: March 2011

In optical experiments with laterally patterned modulation-doped GaAs/AlGaAs quantum wells we observe spatially separate confinement of electrons and holes to one-dimensional quantum wires. We determine the one-dimensional subband spacing and Fermi energy from inelastic light scattering and photoluminescence spectra. From these measurements we directly determine the one-dimensional electron density.
Lattice Mismatch Effects in GaAsP/GaAs and GaAs/GaAsP/GaAs Heterostructures
Authors: Choi Y.W. , Wie C.R. , Vernon S.M.
Published: March 2011

Structural and electrical characteristics of the GaAs1-xPx / GaAs and GaAs/GaAs1-xPx/GaAs (x=0.02, 0.05, 0.08, 0.16 and 0.32) hetero-epitaxial systems have been investigated using X-ray rocking curve technique, Optical Beam Induced Current imaging, Nomarski Micrograph, and I-V-T and C-V measurements. The rocking curve Full Width Half Maximum of the GaAs1-xPx epilayer increased sharply at x=0.16 due to a decreased layer thickness and increased in-plane mismatch. The cross-hatched line density in the OBIC image and Nomarski Micrograph increases as the lattice mismatch increases. The epilayer surface morphology is dependent on the layer thickness. The forward I-V characteristics of Au-GaAsP/GaAs and Au-GaAs/GaAsP/GaAs Schottky diodes showed an increased tunneling current for an the increased lattice mismatch. For GaAsP/GaAs structure with a higher phosphorus composition, Fermi-level pinning caused by misfit dislocation was observed. Au-GaAs/GaAsP/GaAs Schottky diodes show an excess current at the low temperature, high field range which, we believe, is due to defect related tunneling.
A Stable n-Channel Indium Phosphide Field-Effect Transistor with an Amorphous Hydrogenated Silicon Gate
Authors: Roditi E. , Iliadis A.A. , Christou A.
Published: March 2011

InP field-effect transistors fabricated with an amorphous hydrogenated Si (a-Si:H) gate resulted in metal-insulator-like FET characteristics with no observable current drift and a transconductance of 30–38 mS/mm. The high stability of this gate system is attributed to the low temperature of deposition and the hydrogen passivation of the InP surface.
Effects of Oxygen on Diamond Growth
Authors: Harris Stephen J. , Weiner Anita M.
Published: March 2011

In situ mass spectral measurements of the gas composition at the substrate surface were made during filament-assisted diamond growth. The input gases were various mixtures of CH4, O2, and H2chosen in order to discern the effects of oxygen addition on diamond formation and growth. The gas phase chemistry was modeled as a 1-dimensional flow reactor, and the measured and calculated species mole fractions were in good agreement. The model was then used to estimate mole fractions of several atomic and radical species which could not be measured. We find that addition of O2has only a small effect on the radical mole fractions. However, O2can reduce the effective initial hydrocarbon mole fraction, which is important because higher quality diamond is grown at lower initial hydrocarbon mole fraction. Most importantly, perhaps, O2addition leads to the formation of sufficient gas phase OH to remove non-diamond (pyrolytic) carbon from the film. Thus, O2addition allows diamond films to be grown under composition and temperature conditions which otherwise would produce largely non-diamond carbon.
Oxygen Effect in Diamond Deposition at Low Temperatures
Authors: Liou Y. , Inspektor A. , Weimer R. , Knight D. , Messier R.
Published: March 2011

Diamond thin films were deposited on different substrates at low temperatures (lowest temperature∼ 300°C, estimated) in a microwave plasma enhanced chemical vapor deposition (MPCVD) system. The deposited films were amorphous carbon or diamond films depending on the different gas mixtures used. The growth rate of diamond thin films was decreased by adding oxygen to the gas mixture. The addition of oxygen to the gas mixtures was found to be important for diamond growth at low temperatures. Different concentrations of oxygen have been added into the gas mixture. Without oxygen, the deposited films were white soots and easily scratched off. Increasing the oxygen input improved the quality of the Raman peaks and increased the film transpancy. The diamond films were also characterized by scanning electron microscopy (SEM).
Bias Controlled Hot Filament Chemical Vapor Deposition of Diamond Thin Film on Various Substrates
Authors: Lee Y. H. , Ma G.-H. , Bachmann K. J. , Glass J. T.
Published: March 2011

The growth of diamond films on Si(001), polycrystalline Ni, Mo, Ta, and W substrates by biased controlled chemical vapor deposition is discussed. Biasing effects were examined using the Si(001) substrates. The film quality as judged by Raman spectroscopy and scanning electron microscopy depended strongly on the biasing conditions. Under low current reverse bias conditions, highly faceted cubooctahedral polycrystalline diamond growth exhibiting a single sharp Raman line at 1332 cm-1 was obtained. Transmission electron microscopy indicated that these films contained relatively low defect densities and no significant interfacial layers. Biasing into high current conditions which created a plasma resulted in multiply twinned, microcrystalline growth incorporating sp2 bonded carbon into the diamond film. Such films were found to contain very high defect densities and a relatively thick interfacial layer. An investigation of the effects of substrate material was also conducted. Films grown on Si, Ni and W exhibited the best quality. The relationship between this quality and substrate properties such as surface energy and lattice parameter is discussed.
Importance of Filament Reactivity for CVD Diamond Growth
Authors: Sommer M. , Smith F. W.
Published: March 2011

The behavior of tungsten filaments heated up to 2500°C in mixtures of CH4 or C2 H2 and H2 at P = 9 and 25 Torr is analyzed. It has been found that the filament resistance R, spectral emissivity ?, power consumption, and CH4 and C2H2 partial pressures depend critically onl the filament temperature as well as the reactant CH4/ H2 or C2H2/ H2 fraction. We interpret these results on the basis of a thermodynamic model which predicts that transitions between deposition and etching of solid carbon occur on the filament surface at high temperatures. The implications of these results for diamond CVD are discussed. Evidence for gas phase reactions is also presen ted.
Free Standing CVD Diamond Shapes and Coatings
Authors: Patterson Donald E. , Hauge Robert H. , Margrave John L.
Published: March 2011

The success of the emerging CVD diamond film industry will depend to a great extent on how well these films can be put to practical applications. Our research is presently focusing on the development of methods for the growth of large thin wall diamond shapes which can be subsequently strongly bonded to other support materials. The shapes such as cylinders, hemispheres, etc. will be designed to take advantage of diamond's superior hardness and thermal conductivity. As these diamond shapes also promise low friction and long wearing surfaces, they have potential uses as bearing surfaces as well as very scratch resistant covers for mirrors and lenses. Our primary research objectives will be concerned with: 1. The development of various apparatus to grow selected shapes of CVD diamond. 2. The development of techniques to transfer and bond the films onto materials other than the original substrates. 3. The physical and chemical characterization of the diamond films, composites, and final products.
KrF Laser-Induced Chemical Vapor Deposition of Diamond
Authors: Tyndall George W. , Hacker Nigel P.
Published: March 2011

A KrF* (248 nm) laser-based process for the deposition of carbon films containing a large fraction of diamond is reported. The experiment consists of focusing the pulsed laser beam at normal incidence onto the surface of a low temperature (20° - 150° C) silicon substrate in the presence of acetic or malonic acid vapor. The process does not require the presence of hydrogen, although an inert buffer gas, e. g. argon, is usually employed. Deposition rates of approximately 1 μm - hour−1 are obtained, and the presence of diamond in the deposited film is inferred from Raman Spectroscopy and Auger Electron Spectroscopy.
Nuclear Magnetic Resonance Spectroscopy in the Study of Diamond Thin Films
Authors: McNamara Karen Mary , Gleason K. K. , Geis M. W.
Published: March 2011

Nuclear magnetic resonance spectroscopy has been used to study diamond thin films grown in a low-pressure hot-filament reactor from 13C-labeled acetone. Film quality is assessed, and the origin of deposited carbon determined. Carbon atoms from both bonding environments in the acetone molecule deposit to form only sp3-bonded material. The relative rate of incorporation of these carbon atoms is determined. Experimental results and equilibrium calculations demonstrate that CO acts as a precursor for diamond growth in the absence of heterogeneous kinetics.
Photoluminescence Spectroscopy of Diamond Films
Authors: Freitas J. A. , Butler J. E. , Bishop S. G. , Carrington W. A. , Strom U.
Published: March 2011

Photoluminescence spectroscopy has been used to characterize polycrystalline diamond films prepared by filament assisted chemical deposition and by combustion (in an oxygenacetylene flame) techniques. The luminescence spectra of the chemical vapor deposited films are dominated by a defect band possibly associated with a neutral vacancy with a strong zero phonon line at 1.68 eV and weak phonon replicas at lower energies. The combustion films exhibit two additional luminescence bands with zero phonon lines at 1.95 and 2.16 eV. The 1.95 eV band has been tentatively assigned to a nitrogen-vacancy pair. We have also observed a strong dependence of the PL spectra radially across a given combustion film and associated this with details of the flame chemistry.
Laser Emission from Natural Diamonds
Authors: Santos Lucilia , Pereira Estela
Published: March 2011

The red luminescence band which is a strong broad band that occurs in natural diamonds, showing a zero phonon line at 2.145 eV and a coupling to a nearly localized phonon of 30 meV with a Huang-Rhys factor of 10, and a constant intensity up to room temperature, is shown to present tunable stimulated emission at room temperature. The stability of the band towards strong pumping conditions is discussed. Another strong luminescent band (S3) is shown to present excited state absorption.
Electrical Properties of Thin Film and Bulk Diamond Treated in Hydrogen Plasma
Authors: Albin Sacharia , Watkins Linwood
Published: March 2011

Current-voltage characteristics of type Ia synthetic diamond, type IIb natural diamond and free-standing diamond films were measured before and after hydrogenation. The diamond films were polycrystalline, deposited on sacrificial silicon substrates using a microwave chemical vapor deposition process. On hydrogenation, all the samples showed several orders of magnitude increase in conductivity. Hydrogenation was carried out under controlled conditions to study the changes in the I-V characteristics of the samples. The concentration of electrically active hydrogen was determined from the I-V data. Hydrogen passivation of deep traps in diamond is clearly demonstrated.
Doping of Diamond by Co-Implantation with Dopant Atoms and Carbon
Authors: Sandhu G. S. , Kao C. T. , Swanson M. L.
Published: March 2011

We have investigated the challenging problem of doping diamonds, by co-implanting boron, nitrogen or phosphorus together with carbon into natural insulating type -a1 diamonds. All the implantations were done at liquid nitrogen temperature and then the samples were rapidly heated to 1100 °C. Unlike the previous attempts to dope diamond by room temperature or high temperature ion implantations, this method is expected to yield a higher doping efficiency for the implanted atoms. We have characterized the implanted diamonds with electrical and electron spin resonance (EPR) measurements. Boron doped samples showed low electrical resistivities and the EPR signal showed a strong dependence on the boron fluence, indicating a high substitutional fraction of boron atoms. The samples in which nitrogen and phosphorus were co-implanted with carbon showed lower resistivities compared with samples implanted with carbon only. Preliminary thermo-emf measurements indicated n-type conduction in these samples.
Electronic Properties of Diamond/Nickel and Diamond/Boron Nitride Interfaces
Authors: Pickett Warren E. , Erwin Steven C.
Published: March 2011

We present self-consistent local density functional calculations of the electronic structure and bonding characteristics of an ideal diamond/Ni (001) interface and an unrelaxed diamond/BN (110) interface. At this stage the small lattice mismatches are not taken into account. Results include predictions of the band line-ups across the interfaces: the Schottky barrier height in the former case and the valence and conduction band discontinuities in the latter case.
Low Temperature Selective Growth Of β -SiC Using SiH2 Cl2/C3H8/HCl/H2 Gas System
Authors: Ohshita Y.
Published: March 2011

β -SiC is grown on a Si(100) substrate by chemical vapor deposition method under reduced pressure using SiH2 Cl2/C3H8/HCl/H2 gas system. The addition of HCI to SiH2 Cl2/C3H8/HCl/H2 gas system makes it possible to obtain a stoichiometric β -SiC film with a mirror surface at low growth temperature of 900°C. Moreover, β -SiC selective growth on Si(100) surface, with no nucleation on SiO2 surface, is achieved. According to the increase of the HCI flow rate, the density of SiC nucleation on SiO2 surface is greatly decreased. Perfect selective β -SiC film is obtained for HCI concentrations greater than 1.2%.
Ohmic Contacts on β-SiC
Authors: Chaudhry M. I. , Berry W. B. , Zeller M. V.
Published: March 2011

We report on ohmic contacts on β-SiC. The contacts were formed using Ni, NiCr, W, Ti, Wsi2 and TiSi2. Contact resistance measurement and Auger Electron Spectroscopy (AES) were used to study annealing effects on contact materials. Auger analysis of Ni-SiC system indicates that during heat treatment, Ni reacts with Si to form silicide. Similar results are found for NiCr-SiC contacts.

Minimum contact resistance of tungsten and titanium on SiC is measured to be 6.l×10−3 ohm/cm2 and 7.6×10−3 ohm/cm2, respectively. High temperature annealing deteriorates both contacts although for titanium contacts the resistance increases less dramatically as compared to tungsten contacts. The silicides of tungsten and titanium yield lower contact resistance than metallic W and Ti contacts. The contact resistance for Wsi2 and TiSi2 after heat treatment decreases to 3.0×10−4 ohm/cm2 and 1.1×10−4 ohm/cm2, respectively.
Growth of High-Resistivity Wurtzite and Zincblende Structure Single Crystal Gan by Reactive-Ion Molecular Beam Epitaxy
Authors: Powell R. C. , Tomasch G. A. , Kim Y.-W. , Thornton J. A. , Greene J. E.
Published: March 2011

Epitaxial GaN films have been grown at temperatures between 600 and 900 °C by reactive-ion molecular-beam epitaxy. Ga was provided by evaporation from an effusion cell while nitrogen was supplied from a low-energy, single-grid, ion source. The average energy per accelerated N incident at the growing film surface was ≈ 19 eV. Films deposited on Al2O3(0112) and MgO(100)l×l substrates had wurtzite (a-GaN) and metastable zincblende (α-GaN) structures, respectively. The lattice constants were a = 0.3192 nm and c = 0.5196 nm for α;-GaN and a = 0.4531 nm for β -GaN. The room-temperature optical bandgap Eg of zincblende GaN, 3.30 eV, was found to be 0.11 eV lower than that of the hexagonal polymorph α-GaN. All films were n-type with electron carrier concentrations which decreased from 4×1018 to 8×1013 cm−3 with increasing incident N2+/Ga flux ratios between 0.63 and 3.9. Resistivities <106Ω-cm were achieved.
Structural Defects in GaN Epilayers Grown by Gas Source Molecular Beam Epitaxy
Authors: Sitar Z. , Paisley M. J. , Yan B. , Davis R. F.
Published: March 2011

Single crystal cubic or hexagonal GaN thin films have been grown on various substrates, using a modified gas source MBE technique. A standard effusion cell was employed for the evaporation of gallium. A compact electron cyclotron resonance plasma source was used to activate the nitrogen prior to deposition. The films were examined by transmission electron microscopy. The major defects in the wurtzite GaN were double positioning boundaries, inversion domain boundaries, and dislocations. The zinc-blende GaN showed microtwins, stacking faults, and dislocations. The connection between the observed structural defects and the poor electrical properties of GaN is noted.
Vibrational Spectroscopy of Boron Nitride at High Temperatures and Pressures
Authors: Exarhos Gregory Y. , Hess Nancy J.
Published: March 2011

Raman scattering measurements are used to distinguish between amorphous and crystalline phases in sputter deposited boron nitride coatings and bulk materials. Changes in vibrational line frequency and linewidth can be attributed to differences in particle size or inherent strain which can be quantified from pressure-dependent measurements of the bulk material. The response of the Raman-allowed E2g modes (hexagonal phase) to temperature is described by a forced dampeg harmonic oscillator model from which the intra- and interplanar lattice thermal expansion can be estimated.
The Preparation of III-V Semiconductors in Aqueous Solution
Authors: Cumberbatch Toby J. , Putnis Andrew
Published: March 2011

Indium arsenide colloids have been prepared by passing arsine through an aqueous solution of the metal nitrate. Similar experiments with gallium solutions produced an extremely fine precipitate which has been tentatively identified as amorphous gallium arsenide. Attempts to precipitate aluminium arsenide from aqueous solutions or mixed organic solvent systems were unsuccessful. The materials were characterised by transmission electron microscopy, X-ray powder diffraction and and optical absorption spectroscopy.
Fractal-Like Structures Present in Hydrogenated Amorphous and Microcrystalline Silicon
Authors: Geerts M.J. , van Oort R.C. , van den Heuvel J.C.
Published: March 2011

In hydrogenated amorphous silicon NMR studies indicate a twophase structural inhomogenity. Hydrogenated microcrystalline films consist of small crystals with a typical size of 100 Å, embedded in an amorphous web. A hydrogen rf plasma is able to etch both type of films, but with different etch rates. The more crystalline parts of a film are etched more slowly, which makes hydrogen plasma etching a technique that can reveal structural inhomogenities and differences in structural disorder as present, both in amorphous and in microcrystalline silicon films.

Amorphous and microcrystalline films were etched and fractal-like structures were visible when using a SEM at a magnification of 20000 times. In microcrystalline films the fractals form a closed network. The number and typical size of the fractals present in amorphous films can be influenced by the conditions during the deposition.
Picosecond Photomodulation Study of Nanocrystalline Hydrogenated Silicon
Authors: Wraback M. , Chen Lingrong , Tauc J. , Vardeny Z.
Published: March 2011

We have extended our photomodulation studies of nc-Si:H to the picosecond time domain. We measured the decays of photoinduced reflectivity with 100fs temporal resolution as a function of light intensity. Comparison with the data obtained on a-Si:H and c-Si indicates that ultrafast trapping and recombination processes are mainly the properties of the amorphous phase. It has also been observed that nc-Si:H is unstable under high illumination.
Raman Scattering from Microcrystalline Films: Considerations of Composite Structures with Different Optical Absorption Properties
Authors: Nemanich R.J. , Buehler E.C. , LeGrice Y.M. , Shroder R.E. , Parsons G.N. , Wang C. , Lucovsky G. , Boyce J.B.
Published: March 2011

Raman scattering measurements are used to characterize the components of microcrystalline Si and carbon films. A model is described which addresses the properties of Raman scattering from composites of materials of different optical absorption. The analysis shows that the observed spectra are dependent on both the percentage of the components and on the domain size of the more highly absorbing domains. Carbon films produced by different enhanced CVD techniques show both sp2 (graphite) and sp3 (diamond) regions. Silicon films prepared by excimer laser exposure of hydrogenated a-Si and by magnetron sputtering showed features due to both microcrystalline and amorphous regions. The experimental results reflect the length scales of the domains and vibrational excitations.
Role of Surface and Growth-Zone Reactions in the Formation Process of µc-Si:H
Authors: Matsuda A. , Goto T.
Published: March 2011

The role of the surface reaction is discussed in the formation process of µc-Si:H in comparison to that of a-Si:H. It is suggested that the responsible radicals for the formation of µc-Si:H are SiH3 as same in the case of a-Si:H depositions. On the top film-growing surface, a lot of H atoms reach the surface during the course of the μc-Si:H growth giving rise to the change in the surface condition, i. e. the loss probability of SiH3 radicals is increased. At the same time, a full H-coverage of the surface is expected which enhances the surface diffusion of SiH3 radicals, leading to the appearance of a gc nucleus. Moreover, it is speculated that the reaction in the growth zone is not necessary for the nucleation process in µc-Si:H.
The Effect of Hydrogen on the Structure of Amorphous and Microcrystalline Sic Prepared by the Polymer Route
Authors: Chu C-J , Ting S-J. , Bobonneau F. , Mackenzie J.D.
Published: March 2011

Amorphous SiC:H thin films have been deposited on different substrates using metal-organic polymer solutions. The structure of the amorphous phase has been proposed as the rings of Si and C atoms with various sizes. Microcrystalline phase can be produced when fired at temperatures higher than 1000°C. 13C MAS-NMR shows the evidence of the C=C-double bonds. ESR results show the major defects in this material are C-dangling bonds. As predict, defects can be decreased by heat treatment in H2 atmosphere.
Selective Deposition of N+ Doped MC-SI:H:F by Rf Plasma Cvd on Si and S1O2 Substrates
Authors: Baert K. , Deschepper P. , Pattyn H. , Nijs J. , Mertens R.
Published: March 2011

μc-Si:H:F can be deposited by if plasma-CVD of fluorinated gas sources like SiF4 and SiH2F2, mixed with H2 and/or SiH4. However, this growth process is usually not selective: the layers are deposited on SiO2 as well as on Si substrates. In this paper, selective growth from SiF4 + SiH4 is reported. N+ Si layers were deposited on <100> Si and poly-Si with a conductivity up to 300 resp. 100 S/cm. The selective growth process was applied for Source and Drain regions of poly-Si thin film transistors on insulating substrate.
Development of the Very thin Microcrystalline N-Layer and its Application to the Stacked Solar Cell
Authors: Nakabeppu F. , Ishimura T. , Kumagai K. , Fukui K.
Published: March 2011

In order to improve the efficiency of the amorphous silicon stacked solar cells, we have developed the preparation method of highly conductive very thin microcrystalline silicon n-layers. We have found that the addition of a small amount of Ar gas to deposition gases is effective to make microcrystallite size small. The obtained thin films were characterized by conductivity measurement, R-HEED observation and TEM observation.

This newly developed thin microcrystalline n-layers have been applied to the stacked solar cells. Increase of Jsc by 5-6% has been achieved because of the reduction of light absorption loss in n-layer without decrease of Voc and FF.
Microcrystalline Silicon Films Produced by RF Magnetron Sputtering and the Effect of Diffrent Ambients on their Conductivity
Authors: Berjee Ratnabali , Bandyopadhyay A. K. , Sharma S. N. , Patabyal A. K. , Barua A.K.
Published: March 2011

Results on characterisation of undoped, μc-Si:H films prepared by rf magnetron sputtering technique are presented. Highly conducting films (10−3 Δ−cm−1) were obtained at fairly low rf power density (l.2W/cm2). Critical parameters for obtaining microcrystalline phase were identified. The effect of humid ambient on film properties was looked into.