bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ion Damage Studies in GaAs/Al0.6Ga0.4As/GaAs Heterostructures
Authors: Turkot B.A. , Forbes D.V. , Xiao H. , Robertson I.M. , Coleman J.J. , Kirk M.A. , Rehn L. E. , Baldo P. 
Published: March 2011

ABSTRACTThe development of the damage structure produced in (100) GaAs/Al0.6Ga0.4As/GaAs by 1 MeV Kr+ ion irradiation at 77 and 293 K has been investigated by RBS channeling and cross-sectional high-resolution TEM techniques. Following an implantation to a dose of 1014 ions cm-2 at 77 K, RBS channeling spectra indicate that the Al0.6Ga0.4 layer contained a high defect density and was possibly amorphous. Warming to room temperature resulted in a change in the channeling spectrum, which indicated that the damage in the Al0.6Ga0.4As layer had partially recovered. The degree of recovery was greatest at the GaAs/ Al0.6Ga0.4As interface, and decreased with increasing depth. TEM observations show the damage in the Al0.6Ga0.4As to be comprised of planar defects, the density of which increases with depth, and an amorphous layer at the bottom interface. This difference in the damage distribution is consistent with the asymmetry in the channeling spectrum. A model based on the depth variation of cascade density is proposed to account for the observations.
Stresses in Ion Assisted Deposited Oxide Thih Films
Authors: Ghanashyam Krishna M. , Al Robaee Mansour , Kanakaraju S. , Narasimha Rao K. , Mohan S. 
Published: March 2011

ABSTRACTThin films of Ceria, Titania and Ziroonia have been prepared using Ion Assisted Deposition(IAD). The energy of ions was varied between 0 and 1 keV and current densities up to 220 μA/cm were used. It was found that the stress behaviour is dependent on ion species, i.e. Argon or Oxygen, ion energy and current density and substrate temperature apart from the material. While oeria files showed tensile stresses under the influence of argon ion bombardment at ambient temperature, they showed a sharp transition from tensile to compressive stress with increase in substrate temperature. When bombarded with oxygen ions they showed a transition from tensile to compressive stress with increase in energy. The titania films deposited with oxygen ions, on the other hand showed purely tensile stresses. Zirconia films deposited with oxygen ions, however, showed a transition from tensile to compressive stress.
PTCDA Films Deposited by Ionized Beam Method
Authors: Usui Hiroaki , Kashihara Kiyoshi , Tanaka Kuniaki , Miyata Seizo 
Published: March 2011

ABSTRACTThin films of 3,4,9,10-perylenetetracarboxylic-dianhydride (PTCDA) were deposited by an ionized beam method. The molecular orientation and chemical structure of the films were studied in connection with ionization and ion acceleration conditions. At a low ionization condition, the molecules are oriented in parallel with the substrate, and the crystallinity was improved by an appropriate ion acceleration. At higher ionization conditions, on the other hand, ion acceleration resulted in a loss of crystallinity. Deposited molecules undergo chemical change in such a condition, leading to dissociation of dianhydride groups.
Nucleation and Growth of Cubic Boron Nitride Films Produced by Ion-Assisted Pulsed Laser Deposition
Authors: Friedmann T. A. , Medlin D. L. , Mirkarimi P. B. , McCarty K. F. , Klaus E. J. , Boehme D. R. , Johnsen H. A. , Mills M. J. , Ottesen D. K. , Barbour J. C. 
Published: March 2011

ABSTRACTWe are studying the boron nitride system by using a pulsed excimer laser to ablate from hexagonal BN (hBN) targets to form cubic BN (cBN) films. We are depositing BN films on heated (25 - 800°C) Si (100) surfaces and are using a broad-beam ion source operated with Ar and N2 source gasses to produce BN films with a high percentage of sp3-bonded cBN. In order to understand and optimize the growth and nucleation of cBN films, parametric studies of the growth parameters have been performed. The best films to date show >85% sp3-bonded BN as determined from Fourier-transform infrared (FTIR) reflection spectroscopy. High resolution transmission electron microscopy (TEM) and selected area electron diffraction confirm the presence of cBN in these samples. The films are polycrystalline and show grain sizes up to 30- 40 nm. We find from both the FTIR and TEM analyses that the cBN content in these films evolves with growth time. Initially, the films are deposited as hBN and the cBN nucleates on this hBN underlayer. Importantly, the position of the cBN IR phonon also changes with growth time. Initially this mode appears near 1130 cm-1 and the position decreases with growth time to a constant value of 1085 cm-1. Since in bulk cBN this IR mode appears at 1065 cm-1, a large compressive stress induced by the ion bombardment is suggested. In addition, we report on the variation in cBN percentage with temperature.
Ion-Irradiation-Induced Densification of Zirconia Sol -Gel Thin Films
Authors: Levine Timothy E. , Giannelis Emmanuel P. , Kodali Padma , Tesmer Joseph , Nastasi Michael , Mayer James W. 
Published: March 2011

ABSTRACTWe have investigated the densification behavior of sol-gel zirconia films resulting from ion irradiation. Three sets of films were implanted with neon, krypton, or xenon. The ion energies were chosen to yield approximately constant energy loss through the film and the doses were chosen to yield similar nuclear energy deposition. Ion irradiation of the sol-gel films resulted in carbon and hydrogen loss as indicated by Rutherford backscattering spectrometry and forward recoil energy spectroscopy. Although the densification was hypothesized to result from target atom displacement, the observed densification exhibits a stronger dependence on electronic energy deposition.
Growth of CDTE on GaAs and Si Substrates by Organometallic Vapor Phase Epitaxy
Authors: Bhat Ishwara 
Published: March 2011

ABSTRACTEpitaxial (100) CdTe layers have been grown by organometallic vapor phase epitaxy (OMVPE) on GaAs and Si substrates. A thin layer of CdTe was first grown by atomic layer epitaxy (ALE) on GaAs substrates followed by thicker CdTe layer by conventional organometallic vapor phase epitaxy (OMVPE). This process resulted in high quality (100) CdTe on GaAs substrates. On Si substrates, direct growth of CdTe resulted in only polycrystalline layers. Hence, a thin Ge buffer layer grown at low temperature followed by an interfacial layer of ZnTe was used to get high quality (100) CdTe on Si. The process developed here eliminates the high temperature (>850°C) deoxidation step generally required when Si substrates are used. The CdTe layers were characterized by X-ray diffraction and optical microscopy. X-ray rocking curve with full width at half maximum (FWHM) of about 260 arcsec has been obtained for a 4 um thick CdTe layer. The results presented demonstrate novel techniques to control the hetero-interfaces in order to grow high quality CdTe on GaAs and Si substrates.
The Effects of Chemical Vapor Cleaning Chemistries on Silicon Surfaces
Authors: Beck S.E. , Gilicinski A.G. , Felker B.S. , Langan J.G. , Bohling D.A. , George M.A. , Tvankovits J.C. , Rynders R.M. 
Published: March 2011

ABSTRACTThis study explores the effects of two chemical vapor cleaning chemistries on silicon surfaces. The silicon surfaces are not significantly roughened by exposure to either process. Trace amounts of fluorine are found on the surfaces exposed to 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (HFAC). A thin silicon nitride film forms on the silicon surface as a result of exposure to the HMDS process and is attributed to the H2/N2 plasma treatment used in the first step of the process.
Surface Cleaning for Silicon Epitaxy Using Photoexcited Fluorine Gas
Authors: Aoyama Takayuki , Yamazaki Tatsuya , Ito Takashi 
Published: March 2011

ABSTRACTWe studied surface cleaning using photoexcited fluorine gas diluted with hydrogen (UV/F2/H2). We found that UV/F2/H2 cleaning selectively removes native Si oxides from thermal oxides without etching the bulk Si. After UV/F2/H2 cleaning, hydrogen atoms terminate almost all the dangling bonds on the Si surface, and fluorine atoms terminate the few remaining bonds. UV/F2/H2 cleaning also flattens the Si surface. We applied UV/F2/H2 cleaning to Si epitaxy and obtained single-crystal Si films with preannealing and growth temperatures as low as 600°C, 150°C lower than for conventional methods. UV/F2/H2 cleaning is a good dry precleaning method for various processes that include Si epitaxy.
Rapid Evaluation of Thin Film Interfacial Reactions Using Temperature-Ramped Measurements
Authors: Harper J.M.E. , Clevenger L.A. , Colgan E.G. , Cabral C. , Arcot B. 
Published: March 2011

ABSTRACTWe describe an approach for rapid evaluation of thin film interfacial reactions using a combination of temperature-ramped in situ measurements of sheet resistance, calorimetry and stress. Electrical, mechanical and thermal measurements at elevated temperatures provide detailed reaction information which is unavailable in room temperature measurements. Kinetic data is particularly useful in making comparisons with mechanistic models. The following examples are discussed:1. Effects of interfacial oxygen on Ta as a diffusion barrier between Cu and Si,2. Effects of interfacial oxygen on the Cu/Mg reaction to form CuMg2 and Cu2Mg,3. Effects of the density of internal interfaces (grain boundaries) on Al2Cu dissolution and precipitation in Al-Cu alloys.
Adhesion Strength of Cu/Polyimide Measured by Continuous Micro-Wedge Scratch Test
Authors: Wang F. , Nelson J.C. , Huang H. , de Boer M. , Gerberich W.W. , Swisher R.L. 
Published: March 2011

ABSTRACTA modified form of nanoscratch test, continuous micro-wedge scratch technique was applied to characterize the adhesion strength of 0.2 μm thick, 10 μm width sputtered copper fine lines on 50 μm thick solid PMDA-ODA polyimide films. A 20 μm width wedge-shaped diamond tip was used to mechanically debond Cu fine lines to polyimide substrate. Using a microindenter under control depth testing mode, critical loads for delaminations were obtained. The scratch morphology and the debonded areas were observed by scanning electron microscopy. The scratch test results by conical-shaped tip on plain films are also presented here and are compared to the results by wedge-shaped tip in fine metal lines. Practical work of adhesion of 4.1 J/m2 was calculated by FEM based on bimaterial fracture mechanism
Processing High Quality Toughened Zirconia Ceramics by Controlling the Chemistry at the Particle-Particle Interface
Authors: Thuraisingham S.T. , Henshall J.L. 
Published: March 2011

ABSTRACTA novel lower cost wet-processing technique, for producing toughened zirconia ceramics with complex geometries, is presented. It is based mainly on modifications to the particle surface chemistry. The sintered materials produced so far are significantly harder (ca 50%) as well as being tougher (ca 10%) than a commercial CeTZP.
Structural and Film Stress Investigation of the Interfacial Reaction in Al/SiC Microlaminates
Authors: Inturi R. B. , Chinmulgund M. , Shamsuzzoha M. , Barnard J. A. 
Published: March 2011

ABSTRACTThe effect of laminate geometry and thermal treatment on the microstructural evolution of interfacial reaction products and thin film stress in Al/SiC microlaminates has been investigated by x-ray diffraction, transmission electron and optical microscopy, and thin film stress measurements. Both stress-temperature and stress-time studies are conducted. Crystalline Si of two dimensional ‘dendritic’ morphology is observed as a solid state reaction product at the Al/SiC interface following an anneal at 400 °C. This interfacial reaction is associated with a sharp change in thin film stress in laminates with very thin AI layers to a highly compressive state during isothermal annealing at 400 °C of as-deposited laminates. The change in film stress state is in agreement with the expected larger molar volume of the likely product phases.
Surface Steps on (100) MgO Foils Imaged by TEM, SEM and AFM
Authors: King Simon , Heffelfinger Jason , Mallamaci Michael , McKernan Stuart , Carter C. Barry 
Published: March 2011

ABSTRACTThe morphology characteristic of acid-washed and annealed MgO (100) surfaces used as substrates for pulsed-laser deposition (PLD) is studied employing TEM, SEM and AFM. Each of these three microscopal techniques provides information not so readily accessible by and complementary to the other two techniques, leading to a more rounded view of the characteristic morphology of these surfaces.
Ionic Conduction Mechanisms in CaF2 and CaF2-Al2O3 Nanocomposite Films on Al2O3 Substrates
Authors: Modine F. A. , Lubben D. , Bates J. B. 
Published: March 2011

ABSTRACTThin films of pure CaF2 and nanocomposite mixtures of Al2O3 with CaF2 were sublimated on Al2O3 substrates. Interdigital electrodes allowed in situ measurements of the electrical conduction of films as a function of thickness, deposition rate, composition, time, and temperature. The electrical conductivity in pure CaF2 adjacent to an Al2O3 interface sometimes exceeded the bulk CaF2 conductivity (i.e., value at more than 50 nm distance) by as much as a factor of 6700 at 200°C. The high conductivity is characterized by an activation energy of 0.6 ± 0.1 eV, which is significantly lower than the activation energy of about 1.0 eV for conduction in the bulk. However, this high conductivity is thermally unstable and diminishes in time. A high but stable conductivity was obtained in CaF2 films containing about 10 mole percent Al2O3 as a dispersed second phase. At 200°C, a 2-phase film gave a factor of 360 enhancement over the measured bulk CaF2 conductivity and a factor of 7 improvement over the best previously reported conductivity for CaF2-Al203 composite materials. The origin of enhanced conduction in CaF2 is attributed to ion transport along dislocations. Dislocations anneal with a characteristic log of time dependence that is recognizable in the annealing behavior of the electrical conductivity. Presumably, the addition of a dispersed second phase of Al2O3 to CaF2 serves both to generate and to pin dislocations; the electrical conductance is thereby enhanced and stabilized.
The Surface Morphology of Titanium Nitride / Copper Bilayers Annealed at High Temperatures
Authors: Berti Antonio C. , Murarka Shyam P. , Brooke Laura E. 
Published: March 2011

ABSTRACTBilayers of 40 nm titanium nitride and 500 nm copper were sputter deposited on oxidized silicon substrates. The films were annealed for one hour at temperatures from 400° C to 800° C in either vacuum or Ar/H2, ambients. Neither x-ray diffraction or Rutherford backscattering spectrometry indicated any interaction between the titanium nitride and copper films. While no differences in surface morphology were detected at annealing temperatures of less than 500° C, above this temperature a strong dependence on annealing ambient was found. In the vacuum annealed samples, surface grooves formed at the grain boundaries of the copper film. These grooves became progressively larger as the annealing temperature was increased, eventually leading to void formation. Only small grain boundary grooves were present in the Ar/H2, annealed films regardless of annealing temperature. The driving force for the formation of the grooves is believed to be a difference between the grain boundary and surface energies in the copper films. It is speculated that in Ar/H2 anneals this driving force is reduced because hydrogen segregates to the copper grain boundaries and lowers the grain boundary energy.The formation of grooves was found to retard copper grain growth and texturing. Resistivity of the copper film was also found to increase if the void density was sufficiently high.
Ultraviolet (UV) Irradiation Effect on Minority-Carrier Recombination Lifetime in Silicon Wafers with Oxide and Nitride Films
Authors: Zhong L. , Shimura F. 
Published: March 2011

ABSTRACTA new method based upon photoconductance measurement of the minority-carrier recombination lifetime is developed to investigate defects both in dielectric films and on the interface. In this method, surface recombination process in silicon substrate is used as a probe to detect the interface traps generated by ultraviolet (UV) irradiation as well as the defects in a film whose electronic state can be excited by UV irradiation. A variety of films, including native, chemical vapor deposited (CVD) and thermal oxide as well as CVD nitride, have been studied. In CVD nitride, for example, evidence is provided that K-centers, the main charge trapping defects, have a negative correlation energy (negative-U).
Back-Channel Surface Modifications for a-Si:H Thin Film Transistors, TFTs, by Exposure to Plasma Excited N2O
Authors: He S.S. , Stephens D.J. , Lucovsky G. 
Published: March 2011

ABSTRACTWe have studied different surface treatments for the back side of the channel of bottom gate a-Si:H TFTs. Two sets of different (i) channel layer thicknesses, and (ii) gate dielectric silicon nitride compositions were studied. The back channel Si-surfaces were either (i) exposed to products from an N2O plasma, or (ii) plasma oxidized. Comparisons of these back channel passivation methods indicated that relative to oxidized surfaces, the plasma N2O process, which created an oxynitride surface layer, (i) reduced the threshold voltage, (ii) decreased the sub-threshold slope (defined as V/decade of current increase) of the I-V characteristic, and (iii) increased the transconductance, or equivalently, the effective channel mobility.
Finite-Temperature Molecular Dynamics Study for Atomic Structures of Grain Boundary in Transition Metals Fe and Ni
Authors: Chongyu Wang , Wenhui Duan , Quanming Song 
Published: March 2011

ABSTRACTBased on Gauss’ principle of least constraint and Nosé-Hoover thermostat formulation, the numerical algorithms for molecular dynamics simulation are developed to investigate the properties of grain boundary in transition metals Fe and Ni at finite temperature. By the appropriate choice of heat bath parameter, a constant temperature version can be realized. A series of parameters are introduced to describe quantitatively the crystallographic characteristic and the distortion of structure unit. The results indicate the applicability of the calculation mode developed by us and reveal the feature of the atomic structure of grain boundary at finite temperature.
Surface Hardening of Ceramic Oxide and Metal Alloy Single Crystals by Ultrasonic Cavitation
Authors: Brewster James R. , Powell-Friend Y. , Boatner L. A. 
Published: March 2011

ABSTRACTCavitation effects have long been considered to be undesirable phenomena that resulted in the damage and failure of metallic components. In the present work, we establish that, in fact, controlled applications of ultrasonic cavitation phenomena can be used to enhance the surface properties of both ceramics and metals. Polished (100) surfaces of single-crystal MgO and single crystals of 70%Fe-15%Ni-15%Cr (stainless-steel) were subjected to ultrasonically induced cavitation by exposure to 20 kHz excitations (at ∼ 100 W/cm2) in isopropanol. Knoop micro-indentation hardness measurements on untreated and ultrasonically treated areas of the surfaces revealed a hardening that increased with the duration of the ultrasonic treatment up to a saturation level. Relative increases in the surface hardness of up to 30% in the case of MgO and ∼250% in the case of Fe-Ni-Cr were obtained. It was found that the rate of hardening was not uniform over the surface but was more rapid on those portions of the surface that were directly under the edge of the ultrasonically vibrating horn tip.
Fabrication and Characterization of MgO Bicrystals
Authors: Liberatore Michael , Wuensch B.J. , Solorzano I.G. , Sande J.B. Vander 
Published: March 2011

ABSTRACTHigh purity bicrystals of MgO have been grown using chemical vapor transport for the purpose of studying oxygen grain boundary diffusion. Preliminary data indicate preferential diffusion of oxygen along ∑ 13 symmetric tilt boundaries. The measured grain boundary diffusivities were approximately 4 orders of magnitude higher than the corresponding bulk values. The activation energies for bulk and grain boundary diffusion were found to be equal to within experimental error, (≈3.9eV)
Annealing Effects to Electrode Pt / Ti for PZT
Authors: Numata Ken , Aoki Katsuhiro , Fukuda Yukio , Nishimura Akitoshi 
Published: March 2011

ABSTRACTThe application of ferroelectrics such as SrTiO3 or PbZrxTi(1−x)O3 to the insulator of DRAM cell capacitors has been extensively studied. The bottom electrode Pt / Ti for these ferroelectrics needs to be thermally stable because of the crystallization process of ferroelectrics. By varying the annealing temperature from 400°Cto 800°C, we examined the annealing effects to the electrode Pt / Ti by SEM, TEM and in-situ XRD.
Super-Amorphous Alumina Gels
Authors: Pierre A. C. , Uhlmann D. R. 
Published: March 2011

ABSTRACTThe structures of alumina gels made from aluminum sec butoxide have been studied by X-ray diffraction and scanning electron microscopy as a function of pH as well as of the temperature of peptization and gelling. The structures of these gels appear to be very sensitive to the conditions of preparation, and lead to a variety of gelled products and transformation behaviors on firing. Specific attention is directed to preferential orientation and to structures which are X-ray super-amorphous.
Design and Synthesis of Metal-Organic Precursors to Aluminosilicates
Authors: Williams Arlene G. , Interrante Leonard V. 
Published: March 2011

ABSTRACTDiketonate aluminum alkoxides were prepared and allowed to react with acetoxyalkylsilanes. The conversion of the aluminosiloxanes thus obtained to aluminosilicates at 450°C was demonstrated. These aluminosiloxane ceramic precursors are glassy, oligomeric materials which readily dissolve in organic solvents to give viscous solutions ideal for casting films. Films of the metal-organic compounds prepared in this manner yield monolithic, crack-free aluminosilicate films directly on thermal curing, with a thickness limit of 3000Å for single crystal silicon wafer substrates. These aluminosilicate films have been found to be effective anticorrosion barriers for various metal substrates. The chemistry of this organoaluminosilane system and the nature of the aluminosilicate films obtained has been investigated using a variety of chemical and physical methods. The results of this investigation will be described and the possible advantages of this direct conversion process over the sol-gel method as a means of obtaining aluminosilicate films will be discussed.
Precursor Chemistry Effects on Development of Particulate Morphology During Evaporative Decomposition of Solutions
Authors: Gardner Timothy J. , Sproson D. W. , Messing G. L. 
Published: March 2011

ABSTRACTFine-grained, high surface area MgO, NiO and ZnO powders were synthesized by the evaporative decomposition of solutions (EDS) technique at 1000°C from acetate and nitrate salt solutions. The powder characteristics were similar in all cases; however, aggregated powders were obtained from the nitrate salts and aggregate-free powders were obtained from the acetate solutions when reacted in air. This difference is attributed to the oxidation of the acetate radical and/or its residue and that this process acts to disaggregate the salt droplet/particles that are formed during EDS.