bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quasi-Equilibrium Nucleation and Growth of Diamond and Cubic Boron-Nitride
Authors: Bar-Yam Y. , Lei T. , Moustakas T. D. , Allan D. C. , Teter M. P. 
Published: March 2011

ABSTRACTMaterial growth is an inherently non-equilibrium process. However, thermodynamic considerations often provide important insight into material growth, the structure of grown materials, and process control parameters. In essence, thermodynamic considerations are important when activated processes are either slow or fast on the time scale of the growth. Activated kinetic processes are important when their time scale is the same as that of growth. Realistic ab-initio calculations of material structure and dynamics can provide a microscopic understanding of both thermodynamics and the kinetics of material growth. The primary focus of this article is a recently proposed defect-assisted multiple-regrowth stabilization of cubic phases. in this theory the incorporation of vacancies at the growth face changes the relative binding energy of cubic versus hexagonal phases so that diamond and cubic boron nitride can nucleate and grow. This theory predicts that diamond nucleation and growth is enhanced under electron rich or positive ion conditions. Experimental results on growth of both diamond and cubic boron nitride that motivate and support theoretical predictions are described. Cubic boron-nitride grows under off-stoichiometric conditions. The nucleation rate of diamond is increased by many orders of magnitude when a flux of electrons impinges upon the surface. Raman line broadening and ESR measurements indicate the presence of significant concentrations of point defects. Predictions and experimental evidence for both n and p type doping will be discussed. Ab-initio calculations of key kinetic processes and thermodynamic quantities for diamond and boron nitride growth are described.
Interstitial Impurities in Wurtzite Vs. Zincblende Semiconductors: The Case of H In SiC
Authors: Roberson M. A. , Estreicher S. K. 
Published: March 2011

ABSTRACTMost compound semiconductors crystallize in the zincblende or the wurtzite structures. In both cases, all the host atoms are tetrahedrally coordinated. However, the two lattices have no high symmetry interstitial sites in common. As a result, the stability, lowest-energy configuration, electronic structures, and barriers for diffusion of interstitial impurities are in general very different. This situation is illustrated here in the case of interstitial H in 3C (zincblende) and 2H (wurtzite) SiC. The results can be used to obtain the properties of H in other hexagonal polytypes, in particular 6H-SiC.
Diamond Growth from Sputtered Atomic Carbon and Hydrogen Gas
Authors: Kelly Michael A. , Kapoor Sanjiv , Olson Darin S. , Hagstrom Stig B. 
Published: March 2011

ABSTRACTDiamond thin films were grown on a scratched silicon crystal surface by a novel CVD technique. The heated substrate, mounted on a rotating platform, was exposed to a bombardment of sputtered carbon atoms, from a graphite target in a helium plasma, and subsequently bombarded by atomic hydrogen generated by a hot tungsten filament. The resulting diamond films were characterized by Raman spectroscopy and SEM. The SEM images indicate highly faceted diamond crystals and the Raman spectra show a single narrow peak characteristic of pure diamond with no graphitic component. The effective growth rate is about 0.5 microns per hour of exposure time. The novel sequential CVD reactor is described and possible growth mechanisms are discussed.
Preparation and Characterization of 3C-SiC Heteroepitaxial Layers on Si(111)
Authors: Yamanaka Mitsugu , Ikoma Keiko 
Published: March 2011

ABSTRACT3C-SiC layers were grown on Si(111) substrates by chemical vapor deposition (CVD) using SiH4-CH3CI-H2 gas mixture. 3C-SiC(111) heteroepitaxial layers were obtained with smooth surfaces and reduced warpage. All the epilayers were n- type, and the carrier density and Hall mobility were 2.1×1016∼2.8×1017 cm-3 and 120∼180 cm2/Vs at room temperature, respectively. Temperature dependences of the electrical properties of the self-supported 3C-SiC(111) epilayers were measured between 15 and 300 K for the first time. 3C-SiC(111) epilayers showed a similar temperature dependence of carrier density to 3C-SiC(001) heteroepitaxial layer. Hall mobility was maximum (∼360 cm2/Vs) around 100 K.
Hetero-Epitaxial Growth of SiC Films by CVD from Silane, Methane, Propane, and Hydrogen Mixtures
Authors: Bahavar B. , Chaudhiy M. I. , McCluskey R. J. 
Published: March 2011

ABSTRACTEpitaxial silicon carbide films have been produced on Si (100) substrates by CVD with 90% of the carbon supplied by methane and 10% by propane as compared to 100% by propane (or 100% by any carbon source more reactive than methane). This implies a methane to propane mole ratio of thirty. Among possible carbon gases, methane is the purest coimnercially available hydrocarbon source, But methane has not been commonly used for growth of silicon carbide due to its low chemical reactivity. Our process demonstrates the feasibility of achieving high SiC growth rates while using a carbon source that is predominantly methane. We have established that silicon carbide films grown at 1350 °C in a CVD reactor using the above carbon source ratio results in quality single crystalline films at similar growth rates and lower carrier concentrations than fikus grown from propane and silane.The main tools used to characterize the grown films are X-ray and electron diffraction, optical microscopy, surface profilometry, Hall mobility measurements, and thickness measurements.
Electrical and Chemical Characterization of Contacts to Silicon Carbide
Authors: Petit Jeremy B. , Zeller Mary V. 
Published: March 2011

ABSTRACTChemical and electrical studies were performed to determine the characteristics of contacts to 6H-SiC. Both elemental metals (Ni, Mo) and suicides (MoSi2, TaSi2, TiSi2) were studied. Chemical analysis by Auger Electron Spectroscopy (AES) was performed to examine interface reactions caused by heat treatment. Electrical measurements (current-voltage and capacitance-voltage) were made during annealing sequences to determine the rectifying or ohmic characteristics of the contacts. Where possible, barrier height and contact resistance values were calculated.
The CVD Diamond Nucleation Mechanism on Si Overlaid with sp2 Carbon
Authors: Pehrsson Pehr E. , Glesener John , Morrish Arthur A. 
Published: March 2011

ABSTRACTRudder et al. [1] observed heavy (>109 cm-2) diamond nucleation on unscratched Si wafers overlaid with carbon fibers during CVD growth. We demonstrate that the nucleation occurs on the edges of etch pits and carbon-rich particles resulting from reaction between the fibers and the substrate. Both the etch pits and the particles satisfy what we consider to be two necessary conditions for ‘spontaneous’ nucleation; a carbon-saturated surface and high energy sites (unsatisfied valencies) at edges and steps.
The Effects of Substrate Bias and Si Doping on the Properties of Rf Sputtered Bn Films
Authors: Banerjee P.K. , Kim J.S. , Chatterjee B. , Platek M. , Mitra S.S. 
Published: March 2011

ABSTRACTThe effect of substrate bias on the properties of rf sputtered boron nitride films on Si and GaAs substrate were investigated. IR transmission and reflectivity of films with different substrate bias were measured with Perkin Elmer 983 IR spectroscopy. From the IR reflectivity data, transverse optical mode(TO) and longitudinal optical mode(LO) frequencies were derived by fitting Kramer-Kronig model. Absorption coefficient was determined from IR transmission data. The resultant TO and LO modes showed that substrate bias caused broadening of reststrahlen band of rf sputtered boron nitride. We also tried to dope boron nitride films with silicon by alternate sputtering of BN and Si targets controlling sputtering time of each target followed by annealing. Electrical resistivity was measured over the temperature range between 175 K to 370 K for both intrinsic and Si-doped boron nitride films. Intrinsic rf sputtered boron nitride showed Little change in resistivity (109 Ω cm - 1011 Ω cm ) over the temperature range studied. While Si doped BN showed linear change in resistivity with increasing temperature and its activation energy was about 0.22 eV. The effect of substrate bias was also investigated by monitoring the XPS core level spectra of both Bis and N Is peaks, respectively. Substrate bias caused the shift of both B ls and N ls peak to higher binding energy. The effect of substrate bias on refractive index was also studied.
Electrical and Optical Properties of Oxygenated Microcrystalline Silicon (mc-Si:O:H)
Authors: Faraji M. , Gokhale Sunil , Chaudhari S. M. , Takwale M. G. , Ghaisas S. V. 
Published: March 2011

ABSTRACTHydrogenated microcrystalline silicon with oxygen(mc-Si:O:H) is grown using radio frequency glow discharge method. Oxygen is introduced during growth by varying it's partial pressure in the growth chamber. The crystalline volume fraction ‘f’ and the crystallite size ‘δ’ are found to vary with the oxygen content. Results indicate that oxygen can etch the silicon surface when present in low amount while it forms a-SiO2-x with increasing contents. Optical absorption studies in the range of 2 to 3 eV suggest that the absorption coefficient ‘α’ lies in between the values of c-Si and a-Si:H.being closer to a-Si:H. The Hall mobility measurements for these samples indicate that for optimum oxygen contents the mobility as high as 35 cm2 V-1 sec-1 can be obtained. Results on I-V characteristics for p-i-n structure are presented.
Phase Mapping Sputter Deposited Wide Band-Gap Metal Oxides
Authors: Aita C.R. , Lee R.C. , Kwok C.-K. , Kolawa E.A. 
Published: March 2011

ABSTRACTReactive sputter deposition is a widely-used process for growing films of high melting point materials near room temperature and desirable metastable structures not attainable in material grown under conditions of thermodynamic equilibrium. Both categories include wide band-gap metal oxides. A first step towards reproducible growth is to develop a “phase map” for the metal-oxygen system of interest. The map graphically relates independent sputter deposition process parameters, the growth environment, and the metallurgical phase(s) formed in the film. This paper shows how phase maps are constructed and used to observe general trends in oxide phase formation sequence, with examples from the Nb-O, Y-O, and Zr-O systems.
Influence of Substrate Temperature on Tin Oxide Thin Films Deposited by Electron Beam Evaporation Technique
Authors: Rozati S. M. , Mirzapour S. , Takwale M. G. , Marathe B. R. , Bhide V. G. 
Published: March 2011

ABSTRACTTransparent conducting tin oxide films were prepared by an electron beam evaporation technique. As-deposited films were amorphous or polycrystalline depending on the substrate temperature and the time of deposition. In order to get transparent and conducting thin films of SnO2, as-deposited films were subjected to further heat-treatment in air at 650°C for 2 hours. Physical properties of as-deposited and annealed films are discussed with reference to substrate temperature and deposition time.
Effects of Contact Materials on the Thermally Stimulated Current Spectra of Mercuric Iodide
Authors: Bao X. J. , Schlesinger T. E. , James R. B. , Cheng A. Y. , Ortale C. , Van Den Berg L. 
Published: March 2011

ABSTRACTMercuric iodide (HgI2) single crystals deposited with transparent indium-tin-oxide (ITO), and semitransparent gold and nickel contacts were investigated by thermally stimulated current spectroscopy (TSC). The differences in the TSC spectra from these samples indicate that the defect structure in HgI2 may be modified by the contact material. These defects act as carrier traps and have strong implications in the application of HgI2 nuclear detectors. A method of numerical analysis was developed to extract information such as carrier trap activation energy, capture cross-section, and trap concentration-lifetime product from the TSC measurements.
Optical and Magnetic Resonance Investigations of Mercuric Iodide Crystals
Authors: Meyer B.K. , Hofmann D.M. , Eckstein J. , Benz K.W. 
Published: March 2011

ABSTRACTThe optical properties of the red modification of mercuric iodide (HgJ2) were studied by optical absorption, magnetic circular dichroism, photoluminescence and optically detected magnetic resonance investigations. The experiments demonstrate the involvment of acceptors with energy levels at Ev + 0.14 ± 0.01 eV and 0.15 ± 0.01 eV in the absorption and recombination at 2.2 eV. The g - values are 0.85 and 0.74, respectively.
Pzt Interaction with Metal and Oxides Studied by Rutherford Backscattering Spectrometry
Authors: Revesz Peter , Li Jian , Szabo Nicholas , Mayer James W. , Caudillo David , Myers Edward R. 
Published: March 2011

AbstractAnnealing behavior in oxygen ambients of the of the ferroelectric PZT on Hf and Zr electrodes has been studied in the temperature range of 500-800°C using the 3.045MeV O16(∝,∝)O16 resonance in backscattering spectrometry. Internal oxidation of the buried metal electrode was observed. Oxygen concentration of the PZT film decreases with increasing temperature. Pb loss of the PZT film occurred above 700°C.
Polarity and Area Dependence of Reliability Characteristics of Sputitered and Sol-Gel Derived Thin Plzt Films for Dram Applications
Authors: Sudhama C. , Kim J. , Chikarmane V. , Lee J. C. , Tasch A. F. , Myers E. R. , Novak S. 
Published: March 2011

AbstractThe reliability properties of sputtered and sol-gel derived lanthanum doped lead-zirconatetitanate (Pb1-xLax(Zr,Ti)O3) have been studied for DRAM applications. A strong polarity dependence for times-to-breakdown (tbd) and significant space charge effects are observed under constant voltage stressing, and are understood to be related to the movement of oxygen vacancies in the d.c. field. The equilibrium current density attained during d.c. stressing appears to be Schottky emission limited. The endurance of lanthanum doped films to high voltage d.c. stressing improves with increasing lanthanum content and a linear extrapolation of log(tbd) with reciprocal electric field indicates a lifetime of ∼10 years. The low-voltage polarizability of fresh sputtered films depends strongly on the polarity; a.c. stressing leads to hysteresis relaxation. The asymmetry in the response to a.c. stressing is possibly due to the structural asymmetry of the device. Neither tbd nor the fatigue-rate seem to depend on the capacitor area for the areas studied.
PbTiO3 Films Deposited by an Alternating Dual-Target Ion Beam Sputtering Technique
Authors: Cole B.E. , Horning R.D. , Kruse P.W. 
Published: March 2011

AbstractThin films, 0.2 μm to 2 μm thick, of ferroelectric PbTiO3 have been deposit ed on Pt coated Si wafers using a novel dual target ion beam sputtering technique. The sputtering targets of PbO and Ti are shuttled back and forth into a Xe ion beam, depositing very thin (10 - 15 Å) alternating layers of PbO and TiO2. The substrate is heated in situ, allowing interdiffusion of the thin layers into a homogeneous PbTiO3 film. Film composition can be controlled accurately and repeatably by controlling the ratio of the sputtering times from each target. Structural characteristics were analyzed by x-ray diffraction, Rutherford backscattering as a function of the sputtering time ratio and the deposition temperature on Pt and Si3N4 coated Si substrates. The stoichiometric PbTiO3 films have a tetragonal perovskite structure with a slight c-axis preference. Capacitor structures show ferroelectric hysterisis loops, dielectric constants of 100-250, loss tangents between 0.002 and 0.04 and a pyroelectric coefficient greater than 5 x 10−8 C/cm2 °C.
Plasma Enhanced Mocvd of BaTiO3 Films
Authors: Buskirk Peter C. Van , Gardiner Robin , Kirlin Peter S. , Krupanidhi Salora , Nutt Steven 
Published: March 2011

AbstractBulk BaTiO3 has a large linear electro-optic coefficient and a very high dielectric constant. We report results obtained for two different MOCVD processes designed to deposit BaTiO3 films with properties suitable for nonlinear electro-optic or high charge storage applications. Epitaxial BaTiO3 films have been grown on NdGaO3 [100] substrates using a high temperature thermal process; the substrate temperature was 1000°C and the total pressure was 4 torr. Selected area electron diffraction (SAED) measurements indicate highly textured, single phase films on the NdGaO3 substrate which are predominantly [100] oriented. Fine grained polycrystalline films have been grown on Pt at 600°C by plasma-enhanced metalorganic chemical vapor deposition (PEMOCVD). Specular IR reflectance was used to determine the concentration of BaCO3 in the film, which was significantly reduced by the plasma. The polycrystalline films had dielectric constants as large as 300 and resistivities exceeding 5 x 108 Ω-cm at room temperature.
Synthetic Routes to Perovskite Phase Mixed Metal Oxides
Authors: Chandler Clive D. , Hampden-Smith Mark J. , Brinker Jeffrey 
Published: March 2011

AbstractWe are developing strategies to form single-component precursors to perovskite phase mixed metal oxides where the stoichiometry of the precursor is fixed at the molecular level to be that of the final desired phase. These strategies ean be applied to the formation of perovskite phase thin films. Two such methods are described herein, relying on ester elimination and alcohol elimination reactions. We have found the reaction between lead(II) acetate and titanium(IV) isopropoxide in ethanol results in ligand redistribution at room temperature. Reactions between (β-diketonate)2M(OR)2 where M = Ti, Zr and Sn and lead(II) acetate do not result in any detectable ester elimination under the reaction conditions employed, and this approach was not successful. Alcohol elimination experiments have been explored as an alternative strategy using a bifunctional glycolate ligand. Lead carbonate reacted with glycolic acid to form the corresponding lead glycolate complex Pb(O2CCH2OH)2. This compound reacted with (β-diketonate)2M(OR)2, M = Ti and Sn, to eliminate two equivalents of alcohol and form the corresponding single component (β-diketonate)2M(OCH2CO2)2Pb complexes. These complexes start to thermally decompose at 150°C and loss of weight is complete by 450°C to yield a product whose weight loss corresponds to the formation of PbTiO3 for M = Ti. Bulk thermolysis of a sample of (dpm)2Ti(OCH2CO2)2Pb at 400°C resulted in formation of crystalline perovskite phase lead titanate together with PbO, massicot and α-PbO phases.
Fabrication of Sol-Gel Derived Ferroelectric Plzt (9/65/35) Optical Waveguides
Authors: Baude P.F. , Ye C. , Tamagawa T. , Polla D.L. 
Published: March 2011

AbstractCrack free transparent ferroelectric PLZT (9/65/35) thin films were deposited on silicon substrates using the sol-gel deposition technique. An intermediate layer of PLT was used to improve the PLZT's optical quality and to reduce the amount of film cracking. Wet chemical, plasma and reactive ion etching are investigated as means of realizing the necessary waveguide structures. Waveguiding is observed in 2-4mm long PLZT (9/65/35) fabricated by reactive ion beam etching.
Effects of Stoichiometry on Pzt Thin Film Capacitor Properties
Authors: Bernstein S.D. , Kisler Yanina , Wahl J. M. , Bernacki S. E. , Collins S. R. 
Published: March 2011

AbstractThe effects of excess Pb and Zr/Ti ratio on crystallization behavior and ferroelectric properties of sol-gel derived films were studied. Excess Pb was found to reduce the crystallization temperature. Films with good ferroelectric properties (remanent polarization greater than 8 μC/cm2 ) were achieved after 550 °C, 5 minute crystallization. The difference in the magnitude of the charge in response to switching and non-switching pulses was greater than 1 μC/cm2 after 1011 fatigue cycles for many of the films. The arnount of charge remaining after fatigue was found to be dependent on the initial charge. Reducing the partial pressure of oxygen during crystallization affected both the remanent polarization and fatigue behavior. The fatigue rate was relatively independent of composition and crystallization temperature.
Hydrothermal Synthesis of Barium Titanate Thin Films on Titanium Metal Substrates
Authors: Bacsa R. , Ravindranathan P. , Dougherty J.P. 
Published: March 2011

AbstractWell crystallized polycrystalline films of cubic BaTiO3 have been synthesized on Ti metal substrates by the hydrothermal reaction of Ti metal with Ba(OH) 2 in the temperature range 80°C-200°C. The films have been synthesized on Ti foil and also on Ti sputtered Si and polymer substrates. The crystallinity, microstructure and electrical properties depend critically on the nature of the substrate.
Ferroelectric Switching in Lead Zirconatelead Zinc Niobate Thin Films
Authors: Udayakumar K. R. , Schuele P. J. , Chen J. , Brooks K. G. , Cross L. E. 
Published: March 2011

AbstractThin films of PbZrO3-Pb(Zn0.33Nb0.67)03, with PZN contents of 8- 12%, were fabricated through the sol-gel spin-on technique. The structural, low frequency capacitive, and polarization reversal characteristics were investigated as a function of composition in this solid solution system. The switching of ferroelectric polarization was tested by a sequence of square wave pulses consisting of two positive pulses followed by two negative pulses. Compositions with higher PZN contents are promising for switching applications; the films were typically characterized by a switched charge of 4-14 μC/cm2, coercive field of around 30 kV/cm, and relative permittivity of 400-800.
Epitaxial Growth of Ferroelectric Thin Films on GaAs with MgO Buffer Layers by Pulsed Laser Deposition
Authors: Nashimoto K. , Fork D. K. , Ponce F. A. , Geballe T. H. 
Published: March 2011

AbstractEpitaxial growth of ferroelectric thin films on GaAs (100) by pulsed laser deposition was examined for integrated electro-optic device applications. To promote epitaxy of ferroelectrics and prevent interdiffusion, we have deposited several types of buffer layers. CeO2 reacted strongly with GaAs. Although Y203 9% stabilized-ZrO2 films showed epitaxial growth, YSZ reacted with GaAs at 780°C. MgO grew epitaxially and was stable even at 780°C. HRTEM observation showed a sharp interface between MgO and GaAs. BaTiO3 and SrTiO3 deposited on MgO/GaAs structures showed epitaxial growth. In-plane orientation was BaTiO3 [100
// MgO [100] // GaAs [100]. Epitaxial BaTiO3 films were c-axis oriented tetragonal phase and showed ferroelectric hysteresis.
Texturing and Dielectric Properties of Laser Deposited BaTiO3 Thin Films Grown on Heated Substrates
Authors: Vaudin M.D. , Cook L.P. , Wong-Ng W. , Schenck P.K. , Brody P.S. , Rod B.J. , Bennett K.W. 
Published: March 2011

AbstractThin films of BaTiO3 were deposited on platinum-coated silicon substrates using pulsed laser deposition and characterized using electron microscopy, powder x-ray diffraction and electrical measurements. The microstructure consisted of columnar BaTiO3 grains oriented normal to the substrate. Two preferred orientations were observed, with either the (001) or (111) planes of BaTiO3 being parallel to the substrate. The electrical properties of two films were measured and it was found that the (111) film was ferroelectric and the (001) film was not. Possible reasons for this are discussed.