bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Substrate Misorientation on Facet Formation in Selective Area Metalorganic Chemical Vapor Deposition
Authors: Shin Hyunchol , Kwon Young-Se 
Published: April 2011

AbstractWe have investigated the influence of substrate misorientation on facet formation in selective area metalorganic chemical vapor deposition (MOCVD) on GaAs (001) vicinal substrates. Macroscopic steps several hundred angstroms high were generated on the epitaxial layer over triangular voids where the voids were formed using the conditions of the reverse–mesa–shaped facets. AFM observations revealed that the macroscopic steps were formed by the combined effects of the growth rate enhancement and the development of the exact (001) crystallographic surface. Through removing the growth rate enhancement effect from the experiment results, it could be expected that the exact (001) surface developed only on the side for which the (001) surface was exposed because the surface energy of a low index plane was lower than that of a misoriented high index plane.
Microstructure of Compositionally Modulated InAlAs
Authors: Twesten R. D. , Millunchick J. Mirecki , Ahrenkielt S. P. , Zhangt Yong , Lee S. R. , Follstaedt D. M. , Mascarenhast A. , Jones E. D. 
Published: April 2011

AbstractWe have observed spontaneous, lateral composition modulation in tensile InAlAs alloy films grown as short-period superlattices on InP (001). We have analyzed these films using transmission electron microscopy, x-ray reciprocal space mapping, and polarized photoluminescence spectroscopy. We find the growth front is nonplanar, exhibiting ∼2nm deep cusps aligned with the In-rich regions of the compositionally modulated films. In addition to the measured 15nm wavelength modulation in the [110] direction, a modulation of 30nm wavelength is seen in the orthogonal [110] direction. The photoluminescence from the modulated layer is strongly polarized and red shifted by 0.22eV.
Thin Film Growth as a Result of Cluster-Surface Collisions: Computational Simulations
Authors: Qi L. , Sinnott S. B. 
Published: April 2011

AbstractMolecular dynamics simulations have been performed to investigate the chemical and structural processes which occur when molecular clusters of acetylene impact a non-rigid, hydrogenterminated diamond (111) surface at incident hyperthermal kinetic energies. The atoms are characterized by a realistic many-body empirical potential for hydrocarbon systems. The goal is to study the initial stages of thin film growth following impact. Important processes observed during the simulations include polymerization of the cluster molecules, and adsorption (tethering) of some polymer chains to the surface in the initial stages of thin film growth. Further simulations will be necessary to fully determine the characteristics of the film.
STM and X-Ray Diffraction Temperature-Dependent Growth Study of SrRuO3 PLD Thin Films
Authors: Hawley M. E. , Jia Q. X. , Brown G. W. 
Published: April 2011

AbstractSrRuO3 (SRO) has recently found a number of applications in different fields, e. g. as a buffer layer for the growth of high temperature superconductor (HTS) YBa2Cu3O7-x films and as a bottom electrode for ferroelectric or high dielectric constant thin film capacitors and nonvolatile data storage. The growth of high crystallinity SRO films with good structural and electrical properties is the prerequisite for each of these applications. In this paper we describe the affect of one growth parameter, temperature (T), on the crystalline quality, epitaxial substrate relationship and resulting electrical properties. SRO films were deposited on LaAlO3 single crystal substrates by pulsed laser deposition at substrate temperatures (Ts) ranging from room temperature (RT) up to 800° C with a nominal film thickness of 150 nm range. The resulting films were characterized by x-ray diffraction, 4-point transport, and STM.The films' microstructures, as revealed by STM, evolved from polygranular at RT to a layered plate-like structure at higher deposition temperatures, Ts. Increasing Ts was marked first by increasing grain size, then a stronger orientational relationship between film and substrate, finally followed by the development of increased connectivity between grains to an extended island or condensed layered state. The transition from polygranular to layered structure occurred at Ts > 650° C. Increased conductivity paralleled the changes in microstructure. The surfaces of all of the films were relatively smooth; the oriented films are suitable for use as conductive templates in multilayer structures.
Laser Assisted Molecular Beam Deposition of Si, C and Sic Films
Authors: DeLeon R. L. , Sun L. , Rexer E. , Charlebois J. , Garvey J. F. , Forsythe E. W. , Tompa G. S. 
Published: April 2011

AbstractLaser Assisted Molecular Beam Deposition (LAMBD) utilizes a train of gas pulses to precisely control the flux of species generated by laser ablation. We have used the LAMBD technique to ablate Si, C or SiC and grow films on a variety of substrates. These films were deposited as a function of a variety of source growth parameters. Source emission spectra of the Si ablation showed atomic Si and Si+; C ablation showed C atoms. Flux control was implemented by a variation of the laser pulse energy. Flux rates were determined by ablation target mass differences. The films have been analyzed by Raman scattering, SEM, EDX, FTIR, ESCA and surface profile measurements to determine the film structure and composition. These results demonstrate the potential of using LAMBD sources as a means of depositing a variety of high quality single and multiple component films.
Influence of Hcl and H2 on the Heteroepitaxial Growth of 3C-SiC Films on Si(100) Via Low-Temperature Chemical Vapor Deposition
Authors: Edgar J. H. , Gao Y. 
Published: April 2011

AbstractThe roles of HCl and H2 on the low temperature epitaxial growth of 3C-SiC on Si (100) in the SiH4-C2H-HCl-H2 system were examined. At a deposition temperature of 1000 °C with pure H2 as the carrier gas, the deposition rate decreased by approximately 70%, and the structure of the films changed from randomly oriented polycrystals, to textured polycrystals, to single crystals as the Cl/Si gas input ratio was increased from 0 to 40. Without any HCl present, the deposition rate did not change when the H2 carrier gas was replaced with up to 75% He. With a Cl/Si input ratio of 40, the growth rate decreased by approximately 70% as the He fraction was increased to 75%. Films deposited without HCl became more textured as H2 was replaced with He, and single crystal films were produce with a 75% He - 25% H2 mixture as the carrier gas. In contrast, with an input Cl/Si ratio of 40, all films were single crystal, but the rocking curve FWHM increased as H2 was replaced with He.
Nanostructure Study of Ti/TiN Multilayers: Effect of the Deposition Temperature
Authors: Labdi S. , Sant C. , Hennet L. , Houdy Ph. 
Published: April 2011

AbstractIn this paper, we report on the growth and the study of Ti/TiN nanometric multilayers. The preparation of these films has been carried out by high vacuum diode r.f. sputtering. Growth was in-situ monitored by kinetic ellipsometry. Deposition temperature was kept to room and low temperature (-120°C) respectively in order to modify the interface properties and consequently to understand the effect of the interfaces on the film's mechanical properties.The thickness of each layer was varied from 1 nm to 10 nm and alternately repeated in order to obtain a total thickness of 200 nm. After deposition, films were characterized by means of X-ray diffraction and grazing X-ray reflectometry for structural determination. This study shows that the TiN-Ti boundary is composed of TiNx, with x going from the nominal nitrogen concentration of the TiN layer to 0. This can be due either to a surface reaction of the incident titanium during the Ti sequence with the nitrogen present at the film surface or to a reaction of nitrogen with the target surface during the TiN sequence.
Competitive Motions of Grain-Boundary and Free Surface in Selecting Thin Film Morphology
Authors: Sun B. , Suo Z. , Yang W. 
Published: April 2011

AbstractDuring annealing of a polycrystalline thin film, grain-boundaries and film surfaces move. If the grain-boundaries move faster, the grains having the lowest free energy grow at the expense of others, resulting in a continuous film with large grains. If the film surfaces move faster, they groove along their junctions with the grain-boundaries, breaking the film to islands. This paper describes analytic solutions for steady surface motions, and discusses the morphology selection.
Experimental Variables Effecting Chain Growth in Conductive Adhesives
Authors: Hefner Rebecca E. , Palmer Mark A. 
Published: April 2011

AbstractChains of conductive particles within a polymer matrix can be used in place of solder joints in electronics manufacturing. Such materials can be made such that electrical conduction occurs in only one direction. Fabricating such an electrical contact requires that the conducting particles be aligned and touching, thus providing a continuous path. This can be done by applying an electric field to a mixture containing conducting particles in a polymer. Preliminary work will be presented assessing the effect of electric field strength (applied voltage), viscosity (temperature), frequency (DC and AC) on the kinetics of chain formation. A designed experiment showed only viscosity or temperature to be statistically significant. However, it is believed that voltage and frequency are factors which will effect the chain kinetics. Specifically it is proposed that there is an optimal combination of frequency and voltage for chain formation. Based on these results a more systematic study has been proposed.
Vibrational Analysis of a Stearic Acid Adlayer Adsorbed on a Silver Flake Substrate
Authors: Miragliotta Joseph , Benson Richard C. , Phillips Terry E. 
Published: April 2011

AbstractA surface vibrational study of a stearic acid/silver (Ag) flake system is reported. The chemical nature of this interfacial system was examined with surface enhanced Raman scattering (SERS) as a function of sample temperature. The SERS spectrum from the room temperature flake exhibited vibrational peaks that were attributed to a carboxylate species bound to the Ag substrate through the oxygen atoms in the terminal end group. The surface species remained stable to temperatures up to 150 °C, above which a partial decomposition to an amorphous carbon layer was observed. In addition to the Raman studies, an IR‐visible sum‐frequency (SFG) measurement from a stearic acid/smooth Ag substrate proved a useful probe of the C‐H stretches in the terminal methyl group of the molecule. The SFG signal from the asymmetric C‐H stretch in the methyl group exhibited a temperature dependence that was similar to the SERS response from the surface carboxylate group, namely, a marked and irreversible decrease in signal levels for temperatures above 150 °C.
Mechanical Deformation Modeling of Diamond/Gaas Structures
Authors: Strifas Nickolaos , Christou Aris 
Published: April 2011

AbstractIn this study a finite strain elastic-plastic finite element analysis is performed on diamond/GaAs structures. A series of models based upon the principal of superposition are proposed to investigate the mechanical deformation and thermal stress behavior of the diamond/gas structure due to coefficients of thermal expansions (CTE) mismatches. The interfacial shear and peeling stresses in multilayered stacks subjected to uniform temperature variation are studied. Finite strain elastic – plastic analysis is performed on a crack which lies on the interface between the diamond and gas materials. The ductile fracture from the tip of the interface crack, the stress and strain fields and distribution of microvoid volume fraction are analyzed.
A Novel, Low-Cost C-C Composite Heat Sink Material
Authors: Kowbel W. , Chellappa V. , Withers J.C. 
Published: April 2011

AbstractRapid advances in high power electronics packaging require the development of new heat sink materials. Advanced composites designed to provide thermal expansion control as well as improved thermal conductivity have the potential to provide benefits in the removal of excess heat from electronic devices. Carbon-carbon (C-C) composits are under consideration for several military and space electronic applications including SEM-E electronic boxes. The high cost of C-C composits has greatly hindered their wide spread commercialization. A new manufacturing process has been developed to produce high thermal conductivity (over 400 W/mK) C-C composites at greatly reduced cost (less than $50/lb). This new material has potential applications as both a heat sink and a substrate. Dielectric coatings such as A1N and diamond were applied to this new type of heat sink material. Processing, as well as mechanical and thermal properties of this new class of heat sink material will be presented.
Characterization of Metal/A1xIn1-xN Interface Thermal Stability and Electrical Properties
Authors: Qiu Guohua , Chen Fen , Olowolafe J. O. , Swann C. P. , Unruh K. M. , Holmes D. S. 
Published: April 2011

ABSTRACTThe interfaces between metals and semiconductors are very crucial to the performance and reliability of solid-state devices. At the moment information on the interfaces between metals and group III-nitride semiconductors are very rare. In this study, linear I-V characteristics of titanium and aluminum to A1xIn1-xN of three different composition (x=0.18, 0.50,0.85) were obtained exhibiting ohmic characteristics. Specific contact resistance of these metals to A1.18In.82N and Al.5In.5N was measured by transmission line measurement. Interdiffusion between the metals and the semiconductors, induced by annealing in N2 ambient, was determined using RBS and thermal stability was evaluated.
On the Epitaxy of Metal Films on GaN
Authors: Liu Q.Z. , Smith K.V. , Yu E.T. , Lau S.S. , Perkins N.R. , Kuech T.F. 
Published: April 2011

ABSTRACTA variety of metal films deposited at room temperature have been found to grow epitaxially under conventional vacuum conditions on GaN grown by metalorganic vapor phase epitaxy on sapphire substrates. The metal films have been characterized by X-ray diffraction using a thin-film Read camera and by MeV ion channeling measurements. Lattice mismatch between the epitaxial metals and the GaN basal planes ranges from ∼ 0.2% to ∼ 22%, and does not appear to be the determining factor in the epitaxy reported here. Surface structure of the epitaxial metal films has been studied by atomic force microscopy and found to differ considerably from that of nonepitaxial metal films grown on similar GaN substrates.
Influence of Surface Defects on the Characteristics of GaN Schottky Diodes
Authors: Duboz J-Y. , Binet F. , Laurent N. , Rosencher E. , Scholz F. , Harle V. , Briot O. , Gil B. , Aulombard R. L. 
Published: April 2011

ABSTRACTWe have studied the fabrication of Pt/Au Schottky diodes on n-type GaN. We show that the electrical characteristics of the diodes are strongly dependent on the surface chemical treatment before the metal deposition. Lowest leakage currents were obtained by the use of a HC1 solution. We also show that annealing the diode at a moderate temperature (400°C) leads to reduced reverse currents. In order to explain these results, we measured the density of deep levels in the Schottky diode depletion region before and after the annealing process. We did not observe any significant difference in the bulk density of defects due to the anneal. We also studied the temperature dependence of the reverse currents and found a low activation energy. Our results are interpreted in terms of electrical defects at the metal-GaN surface.
MOCVD Growth of GaN Films on Lattice-Matched Oxide Substrates
Authors: Kryliouk O. M. , Dann T. W. , Anderson T. J. , Maruska H. P. , Zhu L. D. , Daly J. T. , Lin M. , Norris P. , Chai H. T. , Kisker D. W. , Li J. H. , Jones K. S. 
Published: April 2011

ABSTRACTThe use of the nearly lattice-matched oxide substrates LiGaO2 and LiAlO2 has been explored for growth of GaN by MOCVD. As compared to the quality of films grown on sapphire, only growth on LiGaO2 yielded good quality films, and required use of nitrogen as the carrier gas. Furthermore, high structural quality films were grown on LiGaO2 at temperatures as low as 850°C. Dislocation densities estimated from cross-sectional TEM micrographs were found to be as low as 107 cm-2 . HRTEM studies revealed deformations at the surface of the LiGaO2 adjacent to deposited GaN films, indicating possible interracial reactions which may affect the film properties. The GaN film orientations corresponded directly to the substrate orientation, viz., ({0001}/{001} and {1102}/{101}).
Growth of GaN by Sublimation Technique and Homoepitaxial Growth by MOCVD
Authors: Sakai Shiro , Kurai Satoshi , Nishino Katsushi , Wada Koichi , Sato Hisao , Naoi Yoshiki 
Published: April 2011

ABSTRACTThe growth of bulk GaN by sublimation method and a homoepitaxial growth by MOCVD are reported. A photo-pumped stimulated emission is obtained from a homoepitaxial layer. The source powder used as a source in the sublimation method is investigated in detail, and it is shown that the powder contains many kinds of compounds consisting mainly of gallium, nitrogen and hydrogen. Growth nucleation control is performed by partly covering an MOCVD-GaN or a scratched-sapphire (0001) by Si02. Hexagonal columns of the size of about 200 μm in diameter and about 200 μm in height are selectively and uniformly grown at the window sites. This technique enables the device processing of crystallites and also helps to increase crystal size by increasing growth time, since it prevents the nucleation of new crystallites which work as sink of the growing species.
Reactive MBE Growth of GaN and GaN:H on GaN/SiC Substrates
Authors: Johnson M. A. L. , Yu Zhonghai , Boney C. , Hughes W. C. , Cook J. W. , Schetzina J. F. , Zhao H. , Skromme B. J. , Edmond J. A. 
Published: April 2011

ABSTRACTReactive N and H, created using rf plasma sources, were used to grow undoped GaN along with p-type GaN:Mg and p-type GaN:Mg:H thin films. By comparing the optical emission spectra from several rf sources with observed GaN grow rates, we deduce that nitrogen atoms and I stpositive series nitrogen molecules (3.95 eV binding energy) are the reactive species responsible for GaN film growth. A Mg ground state acceptor binding energy of about 224 meV was determined from low temperature photoluminescence (PL) experiments for both p-type GaN:Mg and p-type GaN:Mg:H films.
Metalorganic vapor phase epitaxial growth of GaInN/GaN hetero structures and quantum wells
Authors: Scholz F. , HÄrle V. , Steuber F. , Sohmer A. , Bolay H. , Syganow V. , DÖrnen A. , Im J.-S. , Hangleiter A. , Duboz J-Y. , Galtier P. , Rosencher E. , Ambacher O. , Brunner D. , Lakner H. 
Published: April 2011

ABSTRACTGaInN/GaN heterostructures and quantum wells have been grown by low pressure metalorganic vapor phase epitaxy on sapphire using an AIN nucleation layer. We found a significant In incorporation only for growth temperatures of 700°C, although still very high In/Ga ratios in the gas phase had to be adjusted. The In content could be increased by reducing the H2/N2 flow ratio in the main carrier gas. GaInN layers typically show two lines in low temperature photoluminescence which are identified as excitonic-like (high energy peak) and impurity-related-like (low energy) by time-resolved spectroscopy. Quantum wells with a thickness between 8 and 0.5 nm showed only one emission line. The peak of the thinnest wells shows excitonic-like behaviour, whereas we found a smooth transition to an impurity-related-like type with increasing thickness. By scanning transmission electron microscopy studies we found indications for composition fluctuations in these thicker quantum wells which may cause localization effects for the excitons and thus be responsible for the observed optical spectra.
Selected Energy Epitaxy of Gallium Nitride
Authors: Chilukuri R. K. , Zhang Suian , Chen E. , Davis R. F. , Lamb H. H. 
Published: April 2011

ABSTRACTA new apparatus for III-V nitride growth by selected energy epitaxy (SEE) is described. The multi-chamber system comprises a doubly differentially pumped molecular beam source, UHV-compatible growth chamber, x-ray photoelectron spectroscopy (XPS) chamber, UHV transfer line, and loadlock. The growth chamber is equipped for in situ quadrupole mass spectrometry and reflection high-energy electron diffraction (RHEED). Preliminary results of GaN SEE using hyperthermal beams of trimethylgallium (TMG) and ammonia (NH3) are presented.
Mechanisms of Strain Reduction in GaN and AlGaN/GaN Epitaxial Layers
Authors: GfrÖrer O. , Schlüsener T. , Härle V. , Scholz F. , Hangleiter A. 
Published: April 2011

ABSTRACTWe have investigated Al0.12Ga0.88N layers with and without a 1 µm GaN buffer, grown on the c-face of α – Al2O3 substrate with an intermediate AlN nucleation layer grown by LP-MOVPE. We used spatially resolved cathodoluminescence spectroscopy at a temperature of 8K to investigate the strain and the homogeneity of composition that can be determined from the energy of the luminescence peak. The larger thermal expansion coefficient of the sapphire in comparison to the nitrides leads to a biaxial compressive strain of the upper GaN layer when cooling down from growth temperature. For AlGaN layers directly grown on the nucleation layer this cannot be confirmed. The layer stays relaxed and fluctuations in the aluminium composition of 0.4% can be observed. When growing an intermediate GaN buffer, the AlGaN layer gets tensilely strained. This strain is of elastic nature and microcracks can be observed preferentially at the edges due to the smaller lattice constant of AlGaN in comparison to GaN. Even detaching of the AlGaN layers grown on the buffer can be observed. In the regions without cracks the layers are quite homogeneous. A deformation potential of (19±4)eV was estimated for Al0.12Ga0.88N.
N-K-Edge EXAFS Study of Epitaxial GaN Films
Authors: Katsikini M. , Paloura E. C. , Fieber-Erdmann M. , Moustakas T. D. , Amano H. , Akasaki I. 
Published: April 2011

ABSTRACTX-ray absorption measurements at the N and O-K-edges are used to study the local microstructure in cubic and hexagonal GaN films grown by ECR-MBE and HVPE. A distortion in the local microstructure is identified in the 1st nearest neighbor (nn) shell, consisting of Ga atoms, in both the cubic and hexagonal samples. Two N-Ga distances are identified, R1 and R2, where R1 is the expected distance of 1.95Å while R2=R1+0.25Å. The same distortion is detected in the next nn shell containing Ga atoms, where the two distances are 3.7Å and 4.1Å. All the reported distance variations are larger than the error-bar. The nitrogen 2nd nn neighbor is found at the expected distance of 3.12Å while N deficiency is not detected. Finally, the O-Ga distance is found equal to 1.60Å and therefore it can be proposed that the oxygen atom occupies interstitial positions.
High Resolution X-ray Diffraction of GaN Grown on Sapphire Substrates
Authors: Saxler A. , Capano M. A. , Mitchel W. C. , Kung P. , Zhang X. , Walker D. , Razeghi M. 
Published: April 2011

ABSTRACTX-ray rocking curves are frequently used to assess the structural quality of GaN thin films. In order to understand the information given by the line shape, we need to know the primary mechanism by which the curves are broadened. The GaN films used in this study were grown by low pressure metalorganic chemical vapor deposition (MOCVD) on (00•1) sapphire substrates. GaN films with both broad and very narrow (open detector linewidth of 40 arcseconds for the (00•2) GaN reflection) rocking curves are examined in this work. Reciprocal space maps of both symmetric and asymmetric reciprocal lattice points are used to determine that the cause of the broadening of GaN rocking curves is a limited in-plane coherence length.