bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser Writing of High Purity Gold Lines
Authors: Jubber M. , Wilson J.I.B. , Davidson J.L. , John P. , Roberts P.G.
Published: March 2011

Gold tracks have been deposited on thermally oxidised and single crystal silicon, gold and nichrome coated silicon wafers by pyrolytic decomposition of gaseous alkyl (triethyl phosphine) gold(I) complexes using focussed 514 nm radiation from an argon ion laser. The precursors, RAu(I)Et3P, R = CH3, C2H5 are low melting point crystalline solids with relatively high vapour pressures (∼5 mtorr). They are representative of a class of compounds being evaluated for laser deposition of gold. Differential scanning calorimetry, DSC, shows that the thermal decomposition of MeAu(I)Et3P in the solid state is a two-stage process. The decomposition temperature is 63 ± 1°C. Tracks were deposited at laser scan speeds up to 35 μm s−1 with a beam diameter (1/e2) at the focus of ∼12 μm. SIMS, EDX and laser ionisation microprobe analysis, LIMA, were used to determine the chemical composition of the tracks. The purity of >98% is consistent with the measured resistivities (4.2 μΩ cm) at room temperature compared to bulk gold (∼2 μΩ cm). These resistivities were achieved without post deposition annealing. Stylus profilimetry and SEM data showed the lines produced from MeAu(I)Et3P have a virtually rectangular cross-section. Together with the absence of the ubiquitous λ-ripples, this feature suggests that deposition is more rapid on the gold surface than on the SiO2 substrate. Laser power thresholds are lower for silicon substrates coated with thin (5 - 10°A) films of gold or nichrome.
Krf Excimer Laser Deposition of Titanium from Tici4
Authors: Izquierdo R. , Lavoie C. , Meunier M.
Published: March 2011

We have investigated the deposition of titanium lines from TiCl4 induced by KrF excimer laser (248 nm). Substrates are primarily LiNbO3, for the possible formation of Ti:LiNbO3 optical waveguides, as well as silicon and glass. Titanium lines contain [Cl] < 2 at% and are typically 200 to 1000 Angstroms thick with a width ranging from 3 to 20 μm. Results suggest that the process is controlled by photochemistry of TiCl4 but it is difficult at this point to assert which of the gas or adsorbed layer is the primary source of thin film growth.
Laser-Induced Local Decomposition of Adsorbed Tungsten Fluorine Molecules for Metal Deposition on Silicon
Authors: Auvert Geoffroy , Pauleau Yves , Tonneau Didier
Published: March 2011

Decomposition of tungsten hexafluoride on silicon substrates under CW argon laser irradiation in the visible domain has been extensively studied in presence of various buffer or reactive gases. The decomposition rate is found to be limited either by a mass transport phenomena or by a thermally activated process. It has been found that no photolytic decomposition can be invoked as the limiting step in the decomposition rate. Depending on the partial pressure of added hydrogen, irradiation results in a local deposition of tungsten, having good electrical properties. In the high pressure domain, deposition kinetics are consistent with mechanisms invoked in conventional chemical vapor deposition reactors. A different mechanism appearing in a lower hydrogen pressure domain will be tentatively interpreted in correlation with the laser-induced temperature.
The Role of Adsorption and Vapor Pressure in Focused Ion Beam Induced Deposition of Carbon Films
Authors: Kirch S.J. , Seeger D.E.
Published: March 2011

Focused ion beam induced deposition of carbon from various organic molecules was studiedfor a range of temperatures and pressures. To study the effects of vapor pressure, deposition from styrene was compared to deposition from 2-chloro and 2-bromo styrene. To study the effects of the double bond on the vinyl substituent, deposition from ethyl benzeneand 2-bromo ethyl benzene was compared to deposition from the 2-X-styrene materials. Foreach material, deposition yield is found to scale with vapor pressure as a function of temperature over the range studied (0 - 25 C). This behavior shows that physical adsorption plays the key role in determining deposition properties. The importance of the doublebond observed in previous work is simply a manifestation of enhanced physical adsorptiondue to the presence of this double bond.
Mechanism of Chromium Deposition from Cr(CO)6 by Uv Laser Light
Authors: Nowak R. , Hess P.
Published: March 2011

The mechanism of metal film deposition from carbonyls as precursors is discussed in detail. It is shown that different species produced by UV laser irradiation in the gas phase contribute to film growth. Highly reactive species such as metal atoms may be important during the nucleation phase, whereas more stable carbonyls are responsible for the main growth process. This indicates that the main decarbonylation effect occurs at the surface. The higher level of impurity incorporation in chromium films in comparison with nickel films is explained by the relative position of the Fermi level in the d-band of Ni and Cr with respect to the 2π* level of CO, which favors CO bond dissociation in the case of chromium.
Selective Epitaxy of AlxGa1−x as and AlxGal−x as Based Structures
Authors: Goorsky M.S. , Kuech T.F. , Potemski R.
Published: March 2011

Selective epitaxy of AlxGa1−x As by MOVPE was accomplished using diethyl gallium chloride and diethyl aluminum chloride as the metalorganic precursors. Selective epitaxy was achieved for Al containing compounds under certain growth conditions, but AlAs growth was not selective. Quantum wells were selectively grown on masked substrates and unpatterned GaAs wafers; QW luminescence was observed from all samples. Additionally, near gap luminescence was observed from AlxGa1−x, As heterostructures over the entire 550 °C - 850 °C growth temperature range. The ternary alloy composition was found to be a strong function of the gas phase composition and growth temperature. A simple thermodynamic model explained the dependence of growth rate and composition on these parameters.
Optimized Molecular Beam Epitaxy Structures for GaAs on Silicon Photodetectors
Authors: Christou A. , Papanicolaou N.A. , Anderson G.W.
Published: March 2011

Two dimensional growth of GaAs on silicon has been achieved by modulation molecular beam epitaxy (where the arsenic beam is pulsed) with laser assistance at 308 nm (LAMBE). Photoconductive, low doping concentration layers were utilized for metal-semiconductormetal photodetectors which were evaluated at 840 nm.
Atomic Structure of Dislocations and Interfaces in Semiconductor Heterostructures
Authors: Nandedkar A. S. , Sharan S. , Narayan J.
Published: March 2011

We have studied and analyzed critical thickness required for the formation of misfit dislocations in semiconductor heterostructures. The present analysis has been carried out assuming that the nucleation of a misfit dislocation is controlled by the activation energy. The energy of the cohernt interface and the misfit dislocation configuration has been evaluated using a discrete dislocation analysis. Further, atomic structures of coherent and semicoherent interfaces containing misfit dislocations of the type a/2<110={111} ↑ <110= (600 dislocation), a/2<110={001} ↑ <110= (90° dislocation) and a/6<112={111} ↑ <110= (90° partial dislocation) in Ge/Si system were simulated. The total energy, consisting of both core and elastic energy components, was calculated using Stillinger-Weber interatomic potentials. The results show that the energy is a strong function of the nature of dislocations. A 60° dislocation is found to exist in undissociated form in shuffle configuration, but the core contains a dangling bond at the interface. The core of a 90° dislocation reconstructs at the Ge/Si interface with no dangling bonds. The calculated atomic configurations of dislocations and interfaces are found to be in good agreement with high resolution transmission electron microscopy observations.
Atomic Scale Study of Cosi/Si (111) and CoSi2/Si (111) Interfaces
Authors: Catana A. , Heintze M. , Schmid P.E. , Stadelmann P.
Published: March 2011

High Resolution Electron Microscopy (HREM) was used to study microstructural changes related to the CoSi/Si-CoSi/CoSi2/Si-CoSi2/Si transformations. CoSi is found to grow epitaxially on Si with [111]Si // [111]CoSi and < 110 >Si // < 112 >CoSi. Two CoSi non-equivalent orientations (rotated by 180° around the substrate normal) can occur in this plane. They can be clearly distinguished by HRTEM on cross-sections ( electron beam along [110]Si). At about 500°C CoSi transforms to CoSi2. Experimental results show that the type B orientation relationship satisfying [110]Si // [112]CoSi is preserved after the initial stage of CoSi2 formation. At this stage an epitaxial CoSi/CoSi2/Si(111) system is obtained. The atomic scale investigation of the CoSi2/Si interface shows that a 7-fold coordination of the cobalt atoms is observed in both type A and type B epitaxies.
Microstructural Aspects of Nickel Silicide Formation in Evaporated Nickel-Silicon Multilayer Thin Films
Authors: Holloway Karen , Clevenger Larry
Published: March 2011

The early stages of the nucleation and growth of nickel silicides in Ni-Si multilayers evaporated onto oxide-stripped <100> Si substrates and annealed at 150 °C have been studied by cross-section transmission electron microscopy (TEM). Observed differences in the interaction of evaporated Ni with amorphous silicon and single crystal <100> Si have been explained by thermodynamic modeling of the Ni-Si system. The as-deposited films show a 3 nm amorphous Ni-Si intermixed layer at all Ni-Si interfaces, including that with the single-crystal Si substrate. Crystalline Ni2Si formed in all annealed films, consuming the elemental Ni layers. The amorphous alloy layer grows concurrently with Ni2Si during the reaction with a-Si; however, there is no amorphous phase present at the Ni2Si - <100> Si interface. Thermodynamic calculations show that at 150 °C metastable equilibrium might be expected between a-Si, the amorphous phase, and Ni2Si; but not between Ni2Si, the amorphous phase, and crystalline Si. The composition of the amorphous phase is very close to a-Ni50Si50. After a 6 hour anneal at 150 °C, crystalline NiSi forms between the a-Si and the Ni2Si layers by crystallization of the amorphous phase. Further annealing is necessary to form NiSi at the <100> Si - Ni2Si interfaces.
Stranski-Krastanov Growth of Ni on Si(111) at Room Temperature
Authors: Butler J. R. , Bennett P. A.
Published: March 2011

We introduce quantitative Auger lineshape analysis methods to study the room temperature reaction of nickel on Si(111). We show that coexisting phases may be separated by numerically fitting the composite lineshapes using a linear combination of single phase “fingerprint” spectra, obtained by scraping bulk compounds in situ. The reaction proceeds in three stages. For nickel coverage below 1 Å, the growth is layerwise, forming NiSi2. For nickel coverage from 3 to 12 Å, islands of Ni2Si are formed. For nickel coverage above 12 Å, islands of pure nickel are formed. The overlayer reactions appear to be a kinetically limited form of Stranski-Krastanov growth, with multiple compound formation.
X-Ray Absorption Studies of Titanium Silicide Formation at the Interface of Ti Deposited on Si
Authors: Aldrich D.B. , Fiordalice R.W. , Jeon H. , Islam Q. , Nemanich R.J. , Sayers D.E.
Published: March 2011

Near edge X-ray absorption spectra (XANES) have been obtained from the Ti K-edge for several series of titanium silicide samples produced by different techniques. Samples were fabricated by depositing Ti on silicon wafers and subsequently annealing them up to temperatures from 100°C to 900°C in UHV, vacuum furnace, or in a Rapid Thermal Annealing system. Measurements were done in the fluorescence and total electron yield modes. The XANES measurements were correlated with Raman scattering measurements. The XANES data of several reference compounds were obtained, and the data showed a high sensitivity to changes in the film structure. Ti metallic bonding and Ti-Si bonds can be distinguished and their evolution as a function of annealing is related to previous results. For the samples with increased impurities, Ti regions were stable at higher temperatures. The XANES spectra of samples annealed under N2 indicate the formation of a surface nitride.
An NMR Study of Hydrogen in Si02 Films on Silicon
Authors: Levy David H. , Gleason K. K.
Published: March 2011

We have used solid state nuclear magnetic resonance (NMR) spectroscopy to study both “wet” and “dry” thermally grown films of SiO2 on silicon substrates. For the 5000 § wet film, grown at 1050 °C we observed a single Lorentzian line of 6 kHz HWHM (half width at half maximum). For the 500 § dry film, we observed a convolution of two lines: a) a Lorentzian of 4 kHz HWHM and b) a Gaussian of 20 kHz HWHM. The hydrogen distributions in both oxides are interpreted as a function of these lines.
Onset of GaAs Homoepitaxy and Heteroepitaxy
Authors: Biegelsen D K. , Bringans R. D. , Northrup J. E. , Swartz L.-E.
Published: March 2011

We present scanning tunneling microscopy images and atomic models for a variety of GaAs(100) reconstructed surfaces. For homoepitaxial material we show the sequence of phases from c(4×4) through c(8×2) as the As surface concentration is reduced. For the heteroepitaxial GaAs/Si(100) growth we show the first two stages of film development, namely, Si(100):As-(1×2) monolayer coverage followed by adsorption of a submonolayer of Ga dimers. The next stages of film development are discussed.
Low Energy Electron Microscopy of Surface Processes on Clean Si(111) and Si (100)
Authors: Bauer E. , Mundschau M. , Swiech W. , Telieps W.
Published: March 2011

Low energy electron microscopy (LEEM) is briefly introduced and its application to the study of surface defects, surface phase transitions on Si(111), crystal growth and sublimation on Si(100) is illustrated.
The Atomic Geometry of the Reconstructed (001) Surface of the Rutile Phase of SnO2
Authors: Duke Charles B. , Thompson Michael R.
Published: March 2011

The tight-binding total energy formalism developed for tetrahedrally coordinated compound semiconductors has been extended to rutile-structure oxides and applied to calculate the surface atomic geometry and electronic structure of SnO2 (001). Two stable structures, separated by an energy barrier, are found. The first consists of slightly relaxed surface geometry with the top layer oxygen atoms relaxed outward by approximately 0.12A, and cations inward by 0.25A. The second geometry is a more massively reconstructed surface in which the four-coordinate surface Sn atoms attain highly distorted tetrahedral coordination.
Interfacial Superstructures Studied by Grazing Incidence X-Ray Diffraction
Authors: Akimoto Koichi , Mizuki Jun'Ichiro , Hirosawa Ichiro , Matsui Junji
Published: March 2011

Surface superstructures (reconstructed structures) have been observed by many authors. However, it is not easy to confirm that a superstructure does exist at an interface between two solid layers. The present paper reports a direct observation, by a grazing incidence x-ray diffraction technique with use of synchrotron radiation, of superstructures at the interface. Firstly, the boron-induced R30° reconstruction at the Si interface has been investigated. At the a Si/Si(111) interface, boron atoms at 1/3 ML are substituted for silicon atoms, thus forming a R30° lattice. Even at the interface between a solid phase epitaxial Si(111) layer and a Si(111) substrate, the boron-induced R30° reconstruction has been also observed. Secondly, SiO2/Si(100)-2×l interfacial superstructures have been investigated. Interfacial superstructures have been only observed in the samples of which SiO2 layers have been deposited with a molecular beam deposition method. Finally, the interfaces of MOCVD-grown AIN/GaAs(100) have been shown to have 1×4 and 1×6 superstructures.
Bismuth Overlayer Formation on GaAs(110)
Authors: Chang S.-L. , Guo T. , Ford W.K. , Bowler A. , Hood E.S.
Published: March 2011

The temperature and coverage dependent ordering of bismuth overlayers on GaAs(110) is examined using low energy electron diffraction (LEED). Sixth order electron diffraction profiles associated with overlayer ordering are observed at coverages of 0.7, 1.0, and 1.5 monolayers (ML) and for temperatures ranging from -110 C to 200 C. The full-width at half-maxima (FWHM) of the sixth-order spots are examined. Profile analysis reveals narrowing widths with increasing annealing temperature, indicating an improvement of the long-range ordering of the overlayers. Differences in inter- and intrachain ordering are observed, analyzed, and discussed.
Nanolayer Reactions in Aluminum-Metal Interfaces
Authors: Barrera E. V. , Ruckman M. W. , Heald S. M.
Published: March 2011

Surface extended x-ray absorption fine structure (SEXAFS) measurements on the nanometer level were made for AI/M interfaces where M was Cu or Ni. The samples were studied immediately after deposition and after heat treatments. Significant differences in interface reactions were observed depending on deposition direction (Cu on Al or Al on Cu) and the amount of mixing was also related to whether M was Cu or Ni. The SEXAFS measurements revealed that there were no detectable amounts of C or O present. One percent Zn was observed to be in the Al layers. The results obtained from the as-deposited interfaces correlate well with data obtained from buried interfaces of like element combinations.
Measurement of the Relative Position of Adjacent Crystals and the Modelling of Interfacial Structure
Authors: El-Eraki M.H.I. , Kiely C.J. , Pond R.C.
Published: March 2011

Various techniques using transmission electron microscopy for determining the relative position of two crystals separated by an interface are reviewed briefly. Measurements obtained by these means can be used to identify unrelaxed interfacial configurations. The modelling of relaxed configurations based on these unrelaxed candidate structures requires additional information from experimental techniques such as electron diffraction and high resolution microscopy, or theoretical investigation by computer simulation. This procedure is illustrated for a selection of grain and interphase boundaries. {211} grain boundaries between twin related crystals of Al and Ge, and interfaces in NiSi2:Si, CoSi2:Si and AI:GaAs epitaxial systems, are discussed.
A Preliminary Observation on AgGaSe2 as a Nuclear Radiation Detector
Authors: Sakai Eiji , Horinaka Hiromichi , Sonomura Hajimu , Miyauchi Takeshi
Published: March 2011

An about 108 ohm-cm AgGaSe2 crystal of 0.5 mm × 4 mm × 4 mm was polished and contacts were made by evaporating 130 μg/cm2 gold of 3 mm diameter on the two faces of the crystal. The detector was tested using 5.5 MeV alpha-particles at room temperature. Noise increased above an applied bias voltage of 80 V. For + 50 V applied on the electrode opposite to the particle incident electrode, i.e., for electron traversal mode, the preamplifier output pulses showed a risetime of 20 μs and an amplitude of about one-tenth of that obtained from a silicon surface-barrier detector whereas the silicon detector showed a risetime of 0.07 μs. For - 50 V applied on the same electrode, i.e., for hole traversal mode, no pulses were observed.
Fabrication of Ultra High Purity Silicon Single Crystals
Authors: Itoh D. , Kawamoto S. , Miki S. , Namba I. , Yatsurugi Y.
Published: March 2011

High resistivity silicon single crystals for radiation detectors were grown by the floating-zone (FZ) method with and without one-pass zone refining of ultra pure starting material obtained by the decomposition of monosilane gas. In this method, boron is removed from monosilane during gas generation. The main residual impurity is phosphorus from phosphine which is removed with zeolite A after distillation of monosilane. Photoluminescence analysis and an improved 4-point probe resistivity measuring method were used to evaluate the material.
Scintillator Material Growth
Authors: Nestor O. H.
Published: March 2011

Selected aspects of NaI(Tl), Bi4Ge3O12 and CdWO4 growth are addressed. Purity and growth control, dopant level effects, specific imperfections and plastic deformation in large scale commercial production are considered.
Cadmium Telluride Detectors and Applications
Authors: Siffert Paul
Published: March 2011

The current possibilities as well as the limitations today of cadmium telluride photon counters and spectrometers are reviewed. The various types of detectors are considered together with their main characteristics. These detectors are compared with mercuric iodide counters and possible applications of these devices are explained.
The Relaxation of InxGa1-xAs/GaAs Strained Multilayers
Authors: Paine David C. , Howard David J. , Luo Dawei , Sacks Robert N. , Eschrich Timothy C.
Published: March 2011

In this paper we report on the kinetics of strain relaxation in GaAs/InxGa1-xAs/GaAs/AlAs (0.05<x<0.22) layers grown by MBE on GaAs at 520°C. We have characterized the density of dislocations present due to strain relaxation during both film growth and processing by using a large area thinning technique which enables the observation of approximately 2 mm2 areas by plan-view TEM. The thickness of the InxGa1-xAs layers studied was 36.4 nm and four compositions were chosen so that the critical thickness predicted by strain energy considerations was exceeded. Due, however, to sluggish dislocation nucleation and glide kinetics at the deposition temperature, the as-grown misfit dislocation densities were well below the predicted level for fully relaxed films. We have studied the rate at which these metastable strained films relax as a function of post-growth annealing time and temperature.
Surface Cross-Hatched Morphology on Strained III-V Semiconductor Heterostructures
Authors: Chang Kevin H. , Gibala Ronald , Srolovitz David J. , Bhattacharya Pallab K. , Mansfield John F.
Published: March 2011

The correlation between surface cross-hatched morphology and interfacial misfit dislocations in strained III-V semiconductor heteroepitaxy has been studied. The surface pattern is clearly seen on samples grown at high temperature (520°C) and with lattice mismatch f < 2%. A poorly defined cross-hatched morphology is found on layers grown at low temperature (400°C). For f > 2%, a rough textured surface morphology is observed in place of cross hatching. Few threading dislocations are observed in the strained layer when cross hatch develops. Cross hatch occurs after most interfacial misfit dislocations are generated. The results suggest that surface cross hatch is directly related to the generation and glide of interfacial misfit dislocations.
Thermal Stability of Strained InGaAs/GaAs Single Quantum Wells
Authors: Elman B. , Koteles Emil S. , Melman P. , Armiento C.A. , Jagannath C.
Published: March 2011

We present a study of the structural stability of InGaAs/GaAs strained single quantum wells (SQW) grown with a variety of indium compositions and with well widths close to critical thickness values. The samples were grown by molecular beam epitaxy and were subjected to furnace annealing as well as ion implantation followed by rapid thermal annealing. Changes in low temperature photoluminescence linewidths were used to evaluate the stability of strained SQWs. We observed both strain relief, in wide SQWs and strain recovery, in higher indium composition narrow quantum wells which were partially relaxed (low dislocation density) as-grown.
Thermal Disordering of Modulation Doped AlAs/GaAs Superlattice
Authors: Hara Kunihiko , Ito Hiroshi , Ohmi Shinya , Suzuki Takamasa
Published: March 2011

Interdif fusion of Al and Ga in a Si modulation doped AlAs/GaAs superlattice was studied by photoluminescence technique. The diffusion coefficient of Al and Ga in the modulation doped superlattice is 1/3 to 1/2 of that of uniformly doped superlattice with the same average Si concentration. The dependence of the diffusion coefficient on the average Si concentration is similar to that of uniform doping.
Analysis of Strain Relaxation in Au/Ni Multilayers by X-Ray Diffraction
Authors: Chaudhuri J. , Gondhalekar V. , Shah S. , Jankowski A.F.
Published: March 2011

The strain distribution within individual layers in Au/Ni multilayer systems was obtained by an iterative fitting of the experimental x-ray diffraction pattern with a kinematic model. The depth profile of strain in the modulation direction was obtained for these metallic multilayers with repeat periodicities ranging from 1.19 nm to 4.26 nm. It was found that the role of interfacial coherency and strengthening is of great importance in understanding the origin of the supermodulus effect in metallic multilayers.
Epitaxial growth of Cr [001] on LiF [001]
Authors: Mattson J. , Brodsky M. B. , Ketterson J. , You H.
Published: March 2011

We report X-ray diffraction and in-situ RHEED( Reflection High Energy Electron Diffraction) measurements on Cr thin films deposited on LiF[001] single crystal substrates for thicknesses up to 300 nm and for substrate temperatures from 30 to 450°C. From these measurements we determine the range of deposition conditions necessary for epitaxial growth and the stress in these films as a function of film thickness.
Evolution of Stress During Heteroepitaxial Growth of NiSi2 on (001) and (111) Silicon Substrates
Authors: Ho H. L. , Bauer C. L. , Mahajan S.
Published: March 2011

Thin film stresses accompanying the nucleation and growth of NiSi2, resulting from the interaction of polycrystalline nickel films with (001) and (111) silicon substrates, have been measured at an annealing temperature of 825° C. Results Indicate a significantly larger stress reduction during the formation of NiSi2 on (111) silicon ( ~ 200 MPa) whereas the stress reduction is comparatively small (50–100 MPa) for the formation of NiSi2 on (001) silicon. TEM studies reveal that for NiSi2 on (111) silicon, two sets of dislocations in edge or mixed orientation are initially produced - one set consisting of Shockleys spaced 25Onm and a second set consisting of 5Onm spaced Shockleys; dislocations and their Burgers vector lie in the growth interface. For NiSi2 on (001) silicon, dislocations are rarely observed, however, a large concentration of ledges or facets are observed in an orthogonal network lying at the NiSi2 - (001)Si interface.

It is argued thai the observed stress reduction of NiSi2 on (111)Si is due to concurrent dislocation multiplication and interfacial glide of the Shockley partials. Larger compressive stresses of NiSi2 on (111) silicon at the annealing temperature is attributed to the accumulation of the edge type Shockleys present in the NiSi2 phase. In contrast, the negligible decrease in stress during the formation of NiSi2 on (001) silicon is believed to result from the presence of sessile misfit compensating ledges which lie at the NiSi2-Si interface.
Formation of High-Quality Si/CoSi2/Si Double Hetero-Structures by Self-Aligned and Two-Step Molecular Beam Epitaxy
Authors: Miyao Masanobu , Ohshima Takashi , Nakamura Nobuo , Nakagawa Kiyokazu
Published: March 2011

The formation and application of Si/CoSi2/Si double heterostructures are comprehensively studied. A high-quality double heterostructure is formed by two-step molecular beam epitaxy of the Si over layer, i.e., low -temperature growth followed by high-temperature growth. The interfaces between CoSi2 and Si observed by cross-sectional transmission microscopy are atomically abrupt and smooth. In addition, a new fine patterning method of CoSi2 films using self-aligned and selective growth is developed. Finally, permeable base transistors (PBT) with high performance (gm=50 mS /mm) are fabricated using these new techniques.
Fundamental Issues in Heteroepitaxy (Condensed from the Doe Panel Report)
Authors: Peercy P. S.
Published: March 2011

The Department of Energy’s Council on Materials Science convened a Panel charged with assessing the present scientific understanding of epitaxial growth and identifying fruitful research opportunities in this area. The Panel, chaired by Paul S. Peercy, a member of the Department of Energy’s Council on Materials Science and of the Solid State Sciences Committee, was composed of scientists in materials science, physics, and chemistry from academia, government labs and industry. Panel members were: Ernst G. Bauer, Brian W. Dodson, Daniel J. Ehrlich, Leonard C. Feldman, C. Peter Flynn, Michael W. Geis, James P. Harbison, Richard J. Matyi, Pierre M. Petroff, Paul S. Peercy, Julia M. Phillips, Gerald B. Stringfellow and Andrew Zangwill. The Panel met in January, 1989; its activities were supported by the Materials Sciences Division of Basic Energy Sciences. Deliberations emphasized artificially structured materials and resulted in a Panel Report which has been submitted to the Journal of Materials Research. With permission from the Department of Energy, this article excerpts from the report.
Ge Transport and Epitaxy on [111] Si in the Ge/Pd2Si/Si System
Authors: Hong Q. Z. , Zhu J. G. , Xia W. , Mayer J. W.
Published: March 2011

Solid phase epitaxy in the amorphous(a)-Ge/Pd2Si/Si system has been investigated in the temperature range of 600 to 750 °C. The top Ge started to migrate into the suicide layer at 600 °C. After longer time annealing the mixed Ge released from the suicide matrix and formed a laterally uniform epitaxial Ge70Si30 layer on the [111] Si substrate. A minimum yield of 0.1 was achieved for a 800 Å-thick Ge70Ge30 layer.
Characterization of ErAs/GaAs and GaAs/ErAs/GaAs Structures
Authors: Zhu Jane G. , Palmstrøm Chris J. , Mounier Suzanne , Barry Carter C.
Published: March 2011

A series of ErAs/GaAs and GaAs/ErAs/GaAs epilayers have been grown on (100) GaAs substrates by molecular-beam epitaxy. Misfit dislocations at the ErAs/GaAs interface have been analyzed using the weak-beam technique of transmission electron microscopy. The microstructure of GaAs/ErAs/GaAs layers have been characterized using conventional and high-resolution electron microscopy. Twinning inside the upper GaAs layer is the major defect. Although the desired epitactic (100) GaAs on (100) ErAs does dominate, small grains of GaAs with (111) or {122} orientations have been observed at the GaAs/ErAs heterojunction.
Epitaxial growth of Matched Metallic ErP0.6 As0.4 layers on GaAs
Authors: Guivarc'h A. , Le Corre A. , Caulet J. , Guenais B. , Minier M. , Ropars G. , Badoz P.A. , Duboz J.Y.
Published: March 2011

Successful growth of (001 )ErP0.6As0.4 single crystal film on (001) GaAs has been demonstrated. The epitaxial metallic layers reproducibly showed lattice mismatch below 5 10-4. This is, to our knowledge, the first report of a stable, epitaxial and lattice-matched metal/compound semiconductor heterostructure. The ErP0.6As0.4/n-GaAs diodes yielded excellent I-V characteristics with an ideality factor of 1.1 and barrier height of 0.88 eV. For a 240 A-thick film, metallic behavior was observed with resistivities of 25 and 86 µΩcm at 1.5 K and room temperature, respectively. As the other Er compounds ErP, ErAs, ErSb and ErSi2, ErP0.6As0.4 presents an abrupt drop in resistivity in the vicinity of the liquid helium temperature, due to a paramagnetic to antiferromagnetic phase transition.
Strained InGaAs/GaAs quantum wells with a 1.3 µm bandedge at room temperature
Authors: Melman P. , Elman B. , Jagannath C. , Koteles Emil S. , Silletti A.
Published: March 2011

The fabrication of long wavelength opto-electronic devices on GaAs substrates is an attractive method for the monolithic integration of optical and electronic devices on a single chip for applications in telecommunications. InGaAs strained layer quantum wells provide one way of engineering the bandgap needed for 1.3 µm devices at room temperature. We have grown and characterized quantum well structures with bandgap of .96 eV using a novel technique, called spatial strain separation, to avoid the stringent limitation of critical thickness which limits the achievable bandgap in this material system. Moreover we have studied the stability of such structures with respect to thermal processing, including oven and rapid thermal annealing. We have observed no degradation of the quantum wells after thermal annealing as judged from the PL spectra shown here.
Pulsed Laser Atom Probe Analysis of III-V Compound Semiconductor Epilayers.
Authors: Mackenzie Ross A. D. , Alex Liddle J. , Grovenor Chris R. M. , Cerezo Alfred
Published: March 2011

The pulsed laser atom probe has been used to characterise the fine scale chemistry of a range of III-V ternary and quaternary compound semiconductors (GaInAs, AlInAs, GaAlInAs) grown, using MOCVD techniques, on indium phosphide substrates. It has been observed that there are fine scale chemical fluctuations in some specimens on a scale of typically 10–20 nm. The fluctuations appear to be a result of localized clustering of the group III components in the epilayer. In quaternary material there is evidence for different degrees of clustering for different components. It is suggested that this compositional fluctuation is a consequence of clustering occuring above a miscibility gap. The existence of a TEM contrast mechanism inherent to the material has the effect of making TEM an unreliable indicator of fine scale compositional variations in these systems.
Electrical Properties of Mesa Diodes on Epitaxial GaAs/Si
Authors: Jiao K.L. , Soltyka A.J. , Anderson W.A. , Vernon S.M.
Published: March 2011

Deep level transient spectroscopy (DLTS), current-voltage- temperature (I-V-T), capacitance-voltage-temperature (C-V-T), C-T and photoreflectance spectroscopy (PRS) were used to compare the electrical properties of GaAs p-n junctions epitaxially grown by MOCVD on GaAs and Si substrates. EL2 was detected for both GaAs/GaAs and GaAs/Si structures. For GaAs/Si, a continuous distribution of trap levels was also observed which could be ascribed to misfit defects. I-V-T data revealed the saturation current of GaAs/Si diodes to be four orders in amplitude higher than for GaAs/GaAs ones. Different temperature dependences were found in saturation current density, barrier height and capacitance between the two structures. A multistep tunneling model is utilized in explaining the results for GaAs/Si. C-T measurements indicated the free carriers not to be frozen-out for GaAs/Si at the freeze-out temperature of GaAs/GaAs. A defect- induced bandgap tailing effect might be responsible for this effect, verified by PRS tests.
Metastable Electronic Effects in Amorphous Semiconductor Superlattices
Authors: Kakalios J.
Published: March 2011

This paper reviews some of the novel electronic effects observed in amorphous semiconductor superlattices. Quantum size effects have been reported in compositionally modulated amorphous semiconductors based upon optical absorption and tunneling studies. However, the quantum well effects are in direct conflict with transport data estimates of the inelastic scattering length. In doping modulated amorphous semiconductors, a large persistent photoconductivity PPC is observed, which cannot be explained by the field separation model alone, but rather requires the presence of a defect which undergoes a large lattice relaxation upon trapping a charge (similar to the DX center). Studies of npnp amorphous silicon multilayers have enabled a microscopic determination of the process responsible for PPC.
Structural Properties and Thermal Evolution of Fe/Ti Multilayers
Authors: Rodmacq B. , Hillairet J. , Laugier J. , Chamberod A.
Published: March 2011

X-ray diffraction, electrical resistivity and dimensional variation measurements have been performed in order to characterise the structural and transport properties of Fe/Ti multilayers both in the as-prepared state and during thermal annealing. For small periods, the multilayers consist of hep Ti and amorphous iron-rich layers. Increasing the period leads to the crystallisation of the Fe-rich layers, which correlates with a sudden decrease of the electrical resistivity. Depending on the period (that is on the initial structure of the layers), very different types of evolution are observed upon annealing, corresponding to either interdiffusion or preferential diffusion of one of the species.
Magnetic Aftereffect in Compositionally-Modulated Ni/Cu Multilayers Prepared by Electrodeposition and by Sputtering
Authors: Bennett L.H. , Swartzendruber L.J. , Atzmony U. , Lashmore D.S. , Abdul-Razzaq W.
Published: March 2011

A relaxation of the magnetization following a rapid change in the magnetic field has been found in a compositionally-modulated Ni/Cu multilayer produced by sputtering. This finding demonstrates that the relaxation previously found in compositionally-modulated alloys produced by electrodeposition is a property of the material and not an artifact of the electrodeposition process.
Characterization of Modulation Doped Pseudomorphic AlGaAs/InGaAs/GaAs Hemt Structures by Electron Beam Electroreflectance and Photoluminescence
Authors: Herman M. H. , Ward I. D. , Kopf R. F. , Pearton S. J. , Jones E. D.
Published: March 2011

We have investigated the optical transitions present in MBE-grown modulation doped pseudomorphic AlxGa1-xAs/InyGa1-yAs/ GaAs HEMT structures of 120Å InGaAs thickness, y values 0 to 0.28, and x values 0.20 to 0.30. From both 300K electron beam electroreflectance (EBER) and 4K photoluminescence (PL) measurements we observe transitions from the InGaAs strained quantum well layer. The intensity and lineshape of the InGaAs transition in both optical spectra are affected by processing temperatures, and provides an indication of the quality of the HEMT.

In addition to strong, sharp features arising from the GaAs substrate and the superlattice buffer, the EBER data shows important characteristics of the AlGaAs layer which are unavailable from the PL. The latter include the presence of Franz-Keldysh oscillations, from which the crystal quality, composition, and electric field strength within the AlGaAs can be assessed. Specifically, when the growth temperatures are excessive, the disappearance of the Franz-Keldysh oscillations appears to be associated with outdiffusion of In from the strained layer, and consequent deterioration of active device performance.
Electric Field Effects on the Optical Properties of InxGa1-xAs/GaAs Strained Quantum Wells and Superlattices
Authors: Gibb K. , Lacelle C. , Roth A.P. , Soucail B. , Dupuis N. , Voisin P. , Hua B.Y. , Fortin E.
Published: March 2011

We have used photoluminescence excitation and photocurrent spectroscopy to investigate the electronic properties of InxGa1-xAs/GaAs strained layer quantum wells and superlattices. In quantum wells, sharp excitonic transitions between discrete energy levels are observed both in excitation and near flatband photocurrent spectra whereas superlattices show heavy-hole to conduction miniband transitions at the Brillouin mini-zone centre and edge, directly giving the electron miniband width. Applying a longitudinal electric field to the quantum wells produces a red shift of the excitons due to the quantum confined Stark effect, while in superlattices, photocurrent spectra at finite applied electric fields show for the first time in this system, the effects of Wannier-Stark quantization. The analysis of the spectra provides a precise determination of the band offset.
Hot-Carrier Effects on Optical Properties of GaAs/AlxGai1-xAs Quantum Wells
Authors: Chen W.M. , Holtz P.O. , Monemar B. , Sundaram M. , Merz J.L. , Gossard A.C.
Published: March 2011

We report on a study of hot-carrier effects on optical properties of GaAs/AlxGa1-xAs quantum wells, by photoluminescence (PL) spectroscopy in the presence of a microwave (MW) field. Both doped and undoped, multiple quantum wells (MQWs) and single quantum wells (SQWs), grown by molecular beam epitaxy (MBE), show a profound enhancement of free exciton (FE) and bound exciton (BE) (for the doped wells) PL emissions with MW irradiation. This is attributed to effects of hot-carriers induced by the MW electric field. The mechanism responsible for the strong enhancement in PL intensity of the QWs in the presence of hot-carriers is studied, and is discussed in terms of an enhanced carrier trapping by the QWs as a consequence of the MW-induced heating of the photo-excited free carriers in the AlxGa1-xAs barriers.
Anisotropic Transport in InGaAs/GaAs Heterostructures Grown by Movpe
Authors: Sun Qing , Morris D. , Lacelle C. , Roth A.P.
Published: March 2011

Anisotropic electron transport has been observed in InxGa1-xAs/GaAs heterostructures grown by MOVPE on (001) and intentionally misoriented GaAs substrates. The low field electron mobilities in two perpendicular directions are found to be higher in the [110] direction than in the [110] direction. The ratio of µ[110]/µ[110] derived from Hall measurements is related to the degree of substrate misorientation as well as epilayer composition. Finally, the photoluminescence spectra are polarized along orthogonal <110> directions. These anisotropic properties are directly related to the anisotropy of [110] and [110] dislocations due to lattice mismatch between the substrates and the layers.
Application of GaAs-AlGaAs Superlattice Structure for Fabricating High Breakdown Voltage Power MISFET
Authors: Liu W.C. , Lour W.S. , Wang R.L. , Sun C.Y. , Hsu W.C.
Published: March 2011

A new power MISFET with undoped GaAs-Al0.3Ga0.7As superlattice gate “insulator” and buffer structure has been fabricated successfully. The superlattice gate “insulator” exhibits a much higher gate breakdown voltage( >35V) with very low prebreakdown leakage current and a lower gate capacitance (C ). Due to the existence of gate “insulator”, a higher carrier concentration can be employed in the active channel which improves the output drain current capability and transconductance. If the gate length is reduced to 1 um, a higher transconductance up to 330 mS/mm can be expected.

The insertion of superlattice buffer structure, between active channel and buffer layer offers an excellent carrier confinement barrier and gives an interface degraded region smaller than 40A. In addition, the superlattice buffer structure can getter greatly deep level impurities and defects from substrate or buffer layer. In summary, the proposed MISFET structure is suitable for high power, high frequency and low noise applications.
Theory and Experiment: Defect Stabilization of Diamond Films Through Multiple-Regrowth
Authors: Bar-Yam Y. , Moustakas T. D.
Published: March 2011

The growth of diamond is now known to occur by chemical vapor deposition at low pressure even though diamond is thermodynamically unstable to graphite under these conditions. A new quasi-equilibrium theory is discussed which describes how the rapid multiple regrowth of layers with a large concentration of vacancies may stabilize nucleation and growth of diamond. Accurate theoretical calculations show that vacancies raise the energy of graphite more than diamond thus reversing the usual energy balance and leading to the growth of diamond films. One prediction of this theory is that electron rich conditions enhance both growth and nucleation. Experiments display the enhanced growth and nucleation. Raman measurements on diamond films also suggest the presence of a large concentration of defects in the resulting films.
Effect of Doping with Nitrogen and Boron on Cathodoluminescence of CVD-Diamond
Authors: Yokota Y. , Kawarada H. , Hiraki A.
Published: March 2011

We have investigated cathodoluminescence (CL) of nitrogen- and boron-doped CVD diamonds compared with type Ib and undoped CVD diamonds. The CL spectrum of nitrogen-doped CVD diamond shows some luminescent centers, which are not observed in undoped one. Especially 2.15 eV (575 nm) and 1.67 eV (GRl) centers are prominent. CVD diamond doped with both nitrogen and boron shows a similar CL spectrum to boron-doped CVD diamond at lower concentration of nitrogen, and shows a spectrum composed of the centers obtained by nitrogen-doping and by boron-doping at higher concentration of nitrogen. Highenergy electron irradiation to nitrogen-doped CVD diamond produces an intense luminescent center having a zero-phonon line at 3.19 eV, and the following annealing make the emission of 2.15 eV center much more intense.
Electrical Properties of Homoepitaxial Diamond Films
Authors: Gildenblat G. Sh. , Grot S. A. , Hatfield C. W. , Wronski C. R. , Badzian A. R. , Badzian T. , Messier R.
Published: March 2011

We describe the electrical characteristics of boron doped homoepitaxial diamond films fabricated using a plasma assisted CVD process, formation of ohmic contacts, high temperature (580°C) Schottky diodes, and a rudimentary diamond MESFET. We also report reversible changes of the conductive state of the diamond surface by various surface treatments for both natural and thin-film diamonds.
Electrical Contacts to Polycrystalline B Doped Diamond Films
Authors: Nishimura K. , Das K. , Iwase M. , Glass J. T. , Kobashi K.
Published: March 2011

B doped diamond films were synthesized by microwave plasma CVD and electrical contacts were fabricated by R F sputtering. Rc was obtained for Pt, Ni, TaSi2, and Al asdeposited contacts at room temperature. Pt gave the minimum Rc and Al gave the maximum Rc of the metals investigated on films containing a carrier concentration of 5 × 1018/cm3. The minimum Rc, 8.6 × 10−4 Ω cm 2, was obtained on heavily B doped diamond films with a carrier concentration of 2.7 × 1020/cm3. After nnealing at 400 °C, the Rc of Pt contacts on B doped diamond films with a resistivity of 2×104 Ω1 cm decreased by approximately one order of magnitude.
Blue like Diamond Light Emitting Devices to be Massproduced
Authors: Kadono M. , Hayashi S. , Hirose N. , Itoh K. , Inushima T. , Yamazaki S.
Published: March 2011

Recently, there has been considerable interest in electronic device applications of diamond thin films. The chemical properties of diamond is stable. So diamond thin films become very useful if they are used for electronic devices. We consider diamond thin films as blue like emitting devices because diamond has a wide band gap(about 5.5eV). Some light emitting devices have been known [1]. First of all we have been trying to deposit diamond thin films on the large areas. If they deposit on the large areas, light emitting devices may be massproduced.
Doping Effect in Hydrogenated Amorphous Carbon Thin Films by Ion Implantation
Authors: Wong S. P. , Peng Shaoqi
Published: March 2011

Hydrogenated amorphous carbon (a-C:H) thin films have been prepared by rf glow discharge decomposition of C6H5CH3gas at 13.6 MHz. Multi-energy boron or phosphorus implantation into these films has been performed to achieve a relatively flat impurity profile and the doping effect as a function of implanted impurity concentration has been studied. It is found that there are critical values of the implanted boron and phosphorus concentration below which there is no significant change observed in the electrical conductivity activation energy Ea, and the room temperature conductivity σRTincreases only slightly with the impurity concentration. When the critics values are reached, there are first an abrupt decrease in Eaand an abrupt increase in σRT. Then Eadecreases and σRTincreases gradually with further increase in impurity concentraton. The values of the critical concentrations are also found to be dependent on the substrate temperature during deposition. The critical concentrations are lower for lower deposition substrate temperatures. Preliminary results on the comparison between the doping effects by B+and BF2implantation show that the doping efficienty by BF2implantation is much higher.
Optical Band Gap of Diamond-Like Carbon Films as a Function of RF Substrate Bias
Authors: Pastel P. W. , Varhue W. J.
Published: March 2011

Diamond-like carbon films have been deposited with a low temperature 2.45 GHz electron cyclotron resonance plasma enhanced chemical vapor deposition system. The bombarding ion energy was independently controlled with a RF bias to the substrate. The production rate of reactant species and the impinging ion energy are decoupled with this system. The optical band gap decreased from 2.7 to 1.2 eV as substrate bias was increased from 0 to -140 V.