bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ideal Crystal Growth from Kink Sites and Fractional-Layer Growth on GaAs Vicinal Substrate by MOCVD
Authors: Fukui Takashi , Saito Hisao 
Published: March 2011

ABSTRACT(AIAs)1/2(GaAs)1/2 fractional-layer superlattices (FLSs) are grown on (001) vicinal substrates by metalorganic chemical vapor deposition. Various kinds of GaAs substrates are used. When the substrate is misoriented to [110] direction by 1.92° and [110] by 0.10°, uniform superlattice periods in a large surface area are observed with a bright field transmission electron microscope (TEM). The results suggest ideal crystal growth from kink sites during MOCVD growth, and the distances between the kink sites are equal.On a substrate misoriented to [110] by 1.90°, the superlattice periods exhibit an undulation. This shows that kink flow mode growth is not dominant in the [110] direction. On a substrate misoriented to [010[ by 2.0°, no superlattice periods were observed. From the above results, we discuss the growth mechanisms.Polarization dependent photolumlnescence and optical absorption spectra of FLS were also observed. Electron wave interference devices with lateral periodic potential were fabricated.
In-situ Measurement of GaAs Optical Constants and Surface Quality, as Functions of Temperature
Authors: Yao Huade , Snyder Paul G. 
Published: March 2011

ABSTRACTIn-situ spectroscopic ellipsometry (SE) was applied to monitor GaAs (100) surface changes induced at elevated temperatures inside an ultrahigh vacuum (UHV) chamber (<1×10−9 torr base pressure, without As overpressure). The real time data showed clearly the evolution of the native-oxide desorption at ∼577°C, on a molecular-beam-epitaxy (MBE)-grown GaAs (100) surface. In addition, surface degradation was found before and after the oxide desorption. A clean and smooth surface was obtained from an arsenic-capped, MBE-grown GaAs sample, after the arsenic coating was evaporated at ∼350 °C inside the UHV. Pseudodielectric functions <ε>GaAs, from 1.6 eV to 4.5 eV, were obtained through the SE measurements, from this oxide-free surface, at temperatures ranging from room temperature (RT) to ∼610 °C. These <ε> data were used as reference data to develop an algorithm for determining surface temperatures from in-situ SE measurements, thus turning the SE instrument into a sensitive optical thermometer.
Studies of Oxide Desorption From GaAs by Diffuse Electron Scatfering and Optical Reflectivity
Authors: Buuren T. Van , Tiedje T. , Weilmeier M. K. , Colbow K. M. , Mackenzie J. A. 
Published: March 2011

ABSTRACTWe have determined that the temperature for desorption of gallium oude from GaAs increases linearly with oxide thickness, for oxide layers between about 6Å and 26Å thick. Different thicknesses of oxide layers were created by varying the exposure time of the GaAs wafers to a low pressure oxygen plasma. In addition, we show by diffuse light scattering that highly polished GaAs substrates roughen during the oxide desorption. These results are interpreted in terms of a model in which the oxide evaporates inhomogeneously. The oxide desorption was also studied by monitoring the secondary electrons produced by the high energy electrons from the RHEED gun. After the gallium oxide desorption there is a reversible, order of magnitude, increase in the number of secondary electrons produced. We interpret this result as evidence for the formation of microscopic gallium droplets on the GaAs surface.
LPE Growth of Doped Sige Layers Using Multicomponent Phase Diagrams Calculations
Authors: Fleurial J.-P. , Borshchevsky A. , Irvine D. 
Published: March 2011

ABSTRACTHeavy doping of n-type Si-Ge alloys is necessary for improving their high temperature thermoelectric properties. Because of the limited solid solubility of the best dopant available, phosphorus, simultaneous additions of gallium were started several years ago. The substantially higher carrier concentration values obtained in such super-saturated, hot-pressed SiGe/GaP materials point to significant changes in dopant solid solubilities. To better understand the behavior of these alloys, investigation of homogeneous single crystalline materials were needed. As a near-thermodynamic equilibrium technique with processing temperatures well below the melting point of these materials, liquid-phase epitaxy (LPE) was particularly suited to the study of the mechanisms of multidoping. Based on successful crystal growth of Si1-xGex thin films using metals such as Ga, In, Sn and Bi for solvents, several experiments were designed to grow multi-doped SiGe layers with III-V dopant combinations. Knowledge of ternary and quaternary phase diagrams is essential to develop the LPE process. Ternary Si-Ge-M systems computations in good agreement with experimental determinations were used to calculate some of the necessary multicomponent phase diagrams and assess the strength of the various III–V interactions.
Electrical Characterization of Sige Thin Films
Authors: Mccormack J. A. , Fleurial J.-P. 
Published: March 2011

ABSTRACTAn apparatus for measuring electrical resistivity and Hall coefficient on both thin films and bulk material over a temperature range of 300K to 1300K has been built. A unique alumina fixture, with four molybdenum probes, allows arbitrarily shaped samples, up to 2.5 cm diameter, to be measured using van der Pauw's method. The system is fully automated and is constructed with commercially available components. Measurements of the electrical properties of doped and undoped Si-Ge thin films, grown by liquid phase epitaxy reported here, are to illustrate the capabilities of the apparatus.
Electronic Structure of Ru2 Si3
Authors: Pecheur P. , Toussaint G. 
Published: March 2011

ABSTRACTThe electronic structure of Ru2Si3 has been calculated with the empirical tight binding method and the recursion procedure. The calculation strongly indicates that there exists a gap in the structure, which makes Ru2Si3 semiconducting, as found experimentally and explains the stability of the chimney-ladder phases for a valence electron concentration per transition metal atom smaller than 14.
From Garbage to Perfection: A Structural - Chemical view of Thermoelectric Materials
Authors: Tuomi Donald 
Published: March 2011

ABSTRACTThe development of growing markets for thermoelectric devices strongly depends upon improving the performance of the Peltier effect alloys. Breaking out of the specialty niches requires doubling present figures of merit, Z, of commercial alloys though each incremental gain potentially opens additional specialty niches.The alloys are polycomponent, heavily doped, N and P type semiconductors. Optimization to the highest Z's requires controlling bulk phase interactions of phase diagram, compositional, crystal growth, and processing variables influencing the imperfection structures impacting on alloy quality. From the first, the system complexity reeds recognition so the performance optimizing variables become clearly identified. This is crucial to commercial production.The (BiSb)2 (TeSe)3 provide both N and P type alloy model systems useful in understanding 1he general challenge of performance optimization. Illustrations of the imperfection structural chemical limitations on attainable performance by varied technologies are given.In seeking other superior performance alloys the experimental designs for exploratory research need immediately to address the identification of the dominating imperfection variables in order to recognize quickly the potentials present.
Film Materials on the Base of Bi2Te3 and Microbattaries of Them
Authors: Anatychuk Lukyan I. , Pazinkov Valeri V. 
Published: March 2011

ABSTRACTAs, both numerous investigations and practical applications testify, thermobatteries based on film material possess such principal advanteges as high technology and possibility of thermobattery with a great number of legs manufacture-They have also two main drawbacks: relatively small time stability and low efficiency due to shunting of substrate on which thermobattery is formed.
Thin Film Ruthenium Oxide - Iridium Oxide Thermocouples
Authors: Kreider Kenneth G. 
Published: March 2011

ABSTRACTRuthenium oxide and iridium oxide have outstanding resistance to corrosion. These oxides are also excellent electrical conductors and have been used as biochemical charge injection electrodes. Their unique electrical and electrochemical properties have also led to their consideration as high temperature pH electrodes. Thin films are the most useful form for these applications as they permit the miniaturization of fast response sensors and electrodes.This study was used to characterize the thermoelectric and electrical conductance parameters of ruthenium and iridium oxide sputtered thin films. The electric and thermoelectric properties of the thin films were found to be sensitive to the annealing temperature of the sputtered oxides. The properties of the film are related to the microstructure, stoichiometry and crystal structure as determined by x-ray diffraction. Heat treatments were used to stabilize the thermoelectric response and the thermal coefficient of resistivity.
Formation of Silicon-on-Insulator Films from Powders
Authors: Gadepally Kamesh V. , Hawk Roger M. , Brown William D. 
Published: March 2011

ABSTRACTSilicon powders have been successfully deposited by a corona discharge assisted electrostatic process on insulating, semiconducting, and conducting substrates. Subsequently, the deposits were heat treated and films have been formed. We present data pertatining to silicon films on insulators. The insulating surfaces used were sapphire, SiO2 on Si, and Si3N4 on Si. The electrical, chemical, and physical characteristics of these films are presented along with the time and temperature effects on the film formation. The impact of the above method with emphasis to the microelectronics industry will be discussed.
The Research and Development of Silicon-Germanium Thermoelements for Power Generation
Authors: Rosi Fred D. 
Published: March 2011

ABSTRACTOn the 25th of August 1989, radio signals from the unmanned Voyager II spacecraft produced high resolution radio displays of the planet Neptune and its moon, Triton, on the monitors of Caltech's Jet Propulsion Laboratory. Thus ended the 12-year NASA Voyager I and II missions to the giant outer planets of our solar systems. Somewhat overlooked in the excitement over the impressive scientific findings from Voyager's epic planetary encounters was the power system aboard the spacecraft for data collection and signal transmission. This was the multi-hundred watt, radioisotope fueled thermoelectric generator using thermocouple modules made of Si-Ge alloys. The first section of this paper presents a historical review of the research program at the RCA Laboratories in Princeton, N.J. during the 4-year period required for the conception and development of Si-Ge thermoelements for power generation. This includes RCA's strategy in thermoelectric materials research from the viewpoint of device principles and requirements, scientific issues relating to the growth and thermoelectric characterization of Si-Ce alloys, and device feasibility studies. The performance of Si-Ge thermoelements in the power source of several space missions is also discussed. Finally, a perspective is presented on the research management of this remarkably successful program. The second section of the paper describes the results of more recent research on the thermoelectric properties of hot-pressed, sintered Si-Ge alloys and, in particular, the effects of grain size and additions of GaP. In the final section, consideration is given to future areas of research based, in part, on the results of the earlier studies of Si-Ge technology for thermoelectric power generation.
Composite Thermoelectrics - Exact Results and Calculational Methods
Authors: Bergman David J. , Levy Ohad 
Published: March 2011

ABSTRACTA theoretical study of composite thermoelectric media has resulted in the development of a number of simple approximations, as well as some exact results. The latter include exact upper and lower bounds on the bulk effective thermoelectric transport coefficients of the composite and upper bounds on the bulk effective thermoelectric quality factor Ze. In particular, as a result of some exact theorems and computer simulations we conclude that Ze can never be greater than the largest value of Z in the different components that make up the composite.
On the Thermoelectric Power in Ultrathin Films of A3IIB2V Semiconductors Under Magnetic Quantization
Authors: Ghatak Kamakhya P. , De Badal 
Published: March 2011

ABSTRACTAn attempt is made to study the thermoelectric power in ultrathin films of semiconductors under magnetic quantization by including all types of aniso tropies in the energy spectrum within the domain of theory, and taking n-Cd3As2 as an example. It is found that, the magne to-thermopower decreases with increasing surface electron concentration and also changes in an oscillatory manner with film thickness respectively. The theoretical results are in agreement with the experimental observations as reported elsewhere.
Uv-Curable Epoxy Based Second Order Nonlinear Optical Material
Authors: Jeng Ru Jong , Chen Yong Ming , Mandal Braja K. , Kumar Jayant , Tripathy Sukant K. 
Published: March 2011

ABSTRACTEpoxy based material incorporating 4-(4'-nitrophenylazo) phenylamine has been synthesized and subsequently functionalized with cinnamoyl groups. These materials can be easily solution-processed into thin films by spin-coating. The uncrosslinked polymer has excellent thermal and linear optical properties. Glass transition temperature of 115°C and degradation temperature (air) of 278°C were recorded.This material exhibits large second order nonlinear optical (NLO) effects subsequent to poling. In a poled film sample, second harmonic generation coefficient, d33, of 34 pm/V was observed at 1.06 μm. Crosslinking is brought about by exposure to UV radiation at 254 nm wavelength. In a poled and crosslinked film sample, a d33 of 22 pm/V was observed. This d33 value is less than the d33 value of the poled and uncrosslinked film sample due to photo-induced cis-trans isomerization and partial degradation of the NLO chromophores. Nevertheless, the poled and crosslinked film shows a much more stable second order response at ambient conditions compared to the poled film which has not been crosslinked.
Lattice Bending in Poly(Diacetylene) Droplets Near Surfaces
Authors: Wilson Patricia M. , Martin David C. 
Published: March 2011

ABSTRACTDroplets of l, 6-di(N-carbazolyl)-2, 4 hexadiyne (DCHD) diacetylene were prepared by room temperature evaporation of dilute (0.01 wt %) solution of the monomer in chloroform on amorphous carbon-coated mica substrates. HREM and SAED examination revealed small crystallographically textured droplets (∼1 μm diameter) with cracks parallel to the [001] chain direction. The droplet geometry allowed us to investigate the structure of the polymer near edges both parallel and perpendicular to the chain axis. It was found that the curvature of the droplet edge caused a local bending of the polymer crystal lattice. The direct imaging of the molecular organization near the droplet surface allowed an investigation of the mechanisms of lattice bending via the formation of edge dislocations. An understanding of these defects is important in determining how they relate to the optical properties of poly(diacetylenes).
Nonlinear Optical Material Fabrication via Sol-Gel Processing
Authors: Kim Jongsung , Plawsky Joel L. 
Published: March 2011

ABSTRACTNonlinear optical materials which are highly transparent and show large second harmonic generation coefficients were fabricated via the sol-gel process. Nonlinear chromophores were directly incorporated into the silica network by polymerizing chromophore containing organo silanes such as N-[3-(Triethoxysilyl)propyl]-2, 4-dinitrophenylamine (TDP) and 3-(4-Formyl phenoxy)propyl trimethoxy silane (FPT).
Epitaxial Growth of Organic Nonlinear Optical Materials
Authors: Hattori Y. , Mizoguchi A. , Ogaki Y. , Nishimtjra A. 
Published: March 2011

ABSTRACTAs an orientation control technique for organic materials, epitaxial growth on crystal substrates was studied for DBNA, a derivative of p-nitroani1 ine, and polydiacetylene(PDA)-3BCMU using Vacuum Deposition and Molecular Beam Epitaxy(MBE).The thin film of DBNA was epitaxially grown on a KCl(001) surface by Vacuum Deposition. Molecular orientation to the substrate (parallel or normal) was controlled by MBE. PDA-3BCMTJ thin films were prepared by UV light irradiation of DA-3BCMU(monomer) thin films which were epitaxially grown on a KCl(001) surface, x(3) values of this oriented thin film were larger than those of unoriented spin-casted thin film.
Cubic Nonlinear Optical Properties of Thin Films of a Series of Aromatic Schiff Base Polymers
Authors: Yang Chen-Jen , Jenekhe Samson A. , Vanherzeele Herman , Meth Jeffrey S. 
Published: March 2011

ABSTRACTThe third-order nonlinear optical properties of a series of homopolymers and a random copolymer of conjugated aromatic Schiff base polymers have been investigated by picosecond third harmonic generation spectroscopy in the wavelength range 0.9–2.4 um. The off-resonant χ(3)(-3ω;ω, ω, ω) value at 2.4 μm was found to be 1.6×10−12esu for the parent polymer (PPI). 2, 5-Dimethoxy and 2, 5-dihydroxy substitutions or random colpolymerization was found to enhance the nonresonant optical nonlinearity of PPI by a factor of 1.5–4.5. 2-Methyl substitution lowered the χ(3) value. The three-photon resonance enhanced χ(3) of the polymers was in the range l.l×10−11 to 5.2×l0−11 esu. A three-level essential states model was found to describe the observed χ(3) spectra and the resulting fitting parameters were used to explain the observed trends in structure - χ(3) relationships.
Benzthiazole and Thiophene Capped Polyenes for Nonlinear Optical Applications: Single Crystal, Semi-empirical and A b Initio Results
Authors: Yeates A. T. , Dudis D. S. , Resch T. , Fratini A. V. 
Published: March 2011

ABSTRACTThe molecule 2-(2-benzthiazolyl)-1-(2-thienyl)ethene has been studied by x-ray crystallography and has been found to be in the planar conformation with the double bonds in the trans configuration (from the N=C of the benzthiazole to the first double bond in the thiophene). Semi-empirical calculations show this configuration to be the least stable one by 1.5 Kcal/mole. To determine whether this discrepancy is due to crystal packing forces or a deficiency in the semi-empirical methodologies employed, ab initio Hartree-Fock calculations at the RHF/6–31G* level were performed on the four possible planar conformations. A comparison of the AM1 and the Hartree-Fock calculations indicates that while AM1 reproduces the trend in the energy components well, the trend in the total energy is not reproduced well. Comparisons with the experimental structure are also made. Analysis of the second hyperpolarizability indicates an enhancement of the NLO properties of this molecule over that of the uncapped polyenes.
Mechanisms of the Nonlinear Optical Response in Tetraras(Cumylphenoxy)Phthalocyanines
Authors: Flom Steven R. , Shirk James S. , Lindle J. R. , Bartoli F. J. , Kafafi Zakya H. , Pong R. G. S. , Snow Arthur W. 
Published: March 2011

ABSTRACTThe third order nonlinear optical (NLO) response of metal free tetrakis(cumylphenoxy)-phthalocyanine, (H2Pc(CP)4) was investigated at 597 nm, near resonance with the strong Q band. The second hyperpolarizability, γ, and the figure of merit, χ(3)/α, measured with a 1.2 ps pulse. was approximately independent of concentration between a 4.6×10−4 M solution and a neat thin film. The decay of the nonlinear response, however, depended substantially on the concentration and physical state of the material.
Third- and Fifth-Order Optical Properties of Transition Metal Complexes of Benzenedithiol at 1.064 μm
Authors: Lindle J. R. , Weisbecker C. S. , Bartoli F. J. , Pong R. G. S. , Kafafi Z. H. 
Published: March 2011

ABSTRACTTime-resolved degenerate four-wave-mixing studies have been conducted on solutions of transition-metal complexes of benzenedithiol using a 35 ps Nd:YAG laser operating at 1.064 μm. The nonlinear optical properties of the first-row Co(d7), Ni(d8), and Cu(d9) and the d8 group Ni and P t transition metal complexes are discussed.
Excited State Enhancement Mechanism for Nonresonant Nonlinear Optical Processes
Authors: Heflem J. R. , Zhou Q. L. , Rodenberger D. C. , Cai Y. M. , Garito A. F. 
Published: March 2011

ABSTRACTA general enhancement mechanism is discussed for nonlinear optical processes originating from real population of electronic excited states. Enhancement of greater than two orders of magnitude of nonresonant third harmonic generation from an optically pumped s1 electronic excited state is experimentally observed in a conjugated disc-like metallophthalocyanine.
C60 with Metalloporphyrins
Authors: Penicaud Alain , Hsu John , Reed Christopher 
Published: March 2011

ABSTRACTCrII(OEP) (OEP: Dianion of octaethylporphyrin) quantitatively reacts with C60 in a THF-toluene (THF: tetrahydrofurane) mixture to give purple-black crystals of formula Cr(OEP)(C60)(THF)x. ESR and SQUID measurements show this compound to be a salt better described as [Cr(OEP)(THF)2+][(C60)−].THF(x-2). ESR spectra in frozen 2-Me-THF show an anisotropie signal centered at g = 1.998.
Superconductive Properties of CsxRbyC60 (33K) - Isotope Effect -
Authors: Ebbesen T. W. , Tanigaki K. , Saito S. , Mizuki J. , Tsai J. S. , Kubo Y. , Kuroshima S. 
Published: March 2011

ABSTRACTThe surprisingly high Tc for the superconductivity of alkali doped C60 has spurred wide interest in understanding its mechanism [1–7]. We first report the superconductive properties of CsxRbyC60 which has a Tc as high as 33 K when x=2 and y=1 in the feed [4, 5]. SQUID measurements show that in this material the coherence length is 45 A and the penetration depth about 1, 800 A [5]. It has now been proven that the observed increase in the Tc with the size of the alkali dopant is due to the increase in the lattice constant [6]. This is most likely due to the changes in the density of states at the Fermi level. The other important parameter according to BSC theory is the phonon which mediates the electron-electron coupling. In the second part of this paper we present recent results which show that the Tc is indeed strongly influenced by this parameter [7]. The isotope effect is unexpectedly strong on the Tc.
ESR Studies of the Anion Radicals of the Fullerene: C60n- (n = 1, 2, and 3).
Authors: Dubois Dominique , Thomas Jones M. , Kadish Karl M. 
Published: March 2011

ABSTRACTThe results of ESR studies on several anion radicals of the fullerene C60, C60n-(n = 1, 2, and 3), in the solvents benzonitrile, dichloromethane, pyridine and tetrahydrofuran containing 0.1 M TBAClO4 are reported and discussed. The samples are prepared by electrochemical reduction techniques which allow the preparation of samples which contain, quantitatively, the desired anionie species. The results of ESR spectral studies on the anions in frozen solutions as a function of temperature are presented. The ESR lineshapes and linewidths are dependent upon the solvent and the temperature. The g-values are weakly dependent upon temperature. The results obtained from this study are presented and discussed in terms of the unique physical structure and properties of C60.