bluuebunny/crossref_metadata_2025 huggingface dataset:
Processing and the Microstructure of SrTiO3-Based Bl Capacitors using Pb(Fe, W)O3 Ferroelectrics
Authors: Kuwabara Makoto
Published: March 2011

A preliminary experiment was conducted to prepare semiconducting strontium titanate-based internal barrier layer capacitors with ferroelectric Pb(Fe, W)O3 forming insulating layers along the grain boundaries. Processing, microstructure and the dielectric properties of this new type of BL capacitors are described. The idea to obtain this type of BL capacitors with a very high dielectric constant may be realized when the ferroelectric materials can uniformly be diffused along the grain boundaries by using a more sophisticated processing of the second firing.
Plasma-Assisted Chemical Vapor Deposition of Ceramic Films and Coatings
Authors: Davis Robert F.
Published: March 2011

Plasma-assisted chemical vapor deposition uses energetic electrons to decompose reactant gas molecules into more simple and more highly reactant species to achieve deposition of amorphous and crystalline films and coatings at reduced temperatures. The basis of this technique, as well as the deposition conditions and properties of several ceramic films including Al2O3, TiO2, ZnO, AN, BN, TiN, SiC, Si, GaAs, SiC, C (diamond) and GaN, are briefly described. Modifications of the classical immersed method, including remote plasmas, the use of microwave frequencies and electron cyclotron resonance techniques, are also described with material examples.
Laser-Induced Materials Synthesis of Ultrafine Ceramic Particles from Specially Designed Molecular Precursors
Authors: Xiao Tongsan D. , Strutt Peter R. , Gonsalves Kenneth E.
Published: March 2011

The investigation involved the synthesis of Si3N4surface layers on a Ti substrate by a specially designed organosilazane liquid precursor, (CH3SiHNH)xwith x=3 or 4, by pyrolysis with a 10.6 μm. continuous wave CO2laser. Microstructural examinations revealed that the particles of the nitride layers were spherical in shape with diameters ranging from 50 to 150 nm. Based on the experimental evidence, suggestions are made of possible mechanisms occurring during film deposition.
Powder Processing and Densification of Ceramic Composites
Authors: Lange Fred F. , Lam David C. C. , Sudre Olivier
Published: March 2011

Two issues, packing powder/reinforcement systems and constrained densification, are reviewed. It is shown that pressure filtration has the greatest potential for packing powders containing reinforcements and packing powders within reinforcement preforms. High particle packing is achieved with repulsive interparticle potentials, and for a very small particle to reinforcement diameter ratio. It is now clear that individual reinforcements do not constrain the densification of powders. Shrinkage constraint is caused by a network of either nontouching or touching reinforcements. Network shrinkage (and thus composite shrinkage) caused by powder densification leads to the development of a denser interconnected matrix material surrounding lower density regions. Densification of the lower density regions requires the creep deformation of the denser continuum. As detailed elsewhere in this proceedings, grain growth causes this denser continuum to become more resistant to creep, and coarsening within the lower density regions causes desintering and the dissipation of sintering ‘stresses’. These phenomena do not occur during the densification of glass powders and explains the different densification behavior of crystalline powder matrices relative to glass powder matrices.
Preparation and Characterization of Colloidal ZnS Particles
Authors: Celikkaya Ahmet , Akinc Mufit
Published: March 2011

The preparation of particles of uniform size, shape, and composition has been of interest to colloid chemists and has received serious attention in the ceramic processing community recently. I interest in making monodispersed sols is not based solely on esthetic appeal of such systems but has evolved from high tech applications which place stringent requirements on the properties of ceramic components and thus on starting powders. Uniform particle size and shape are also essential for the evaluation of validity of various sintering models as well as optical, magnetic and electrokinetic properties of colloidal systems developed assuming uniform particle size and shape.
The Morphology of Freeze-Dried Rubidium Chloride Powder
Authors: Panitz J. K. G. , Voigt J. A. , Greulich F. A. , Carr M. J. , Eatough M. O.
Published: March 2011

We have formed powders of a strongly ionic compound, RbCl by freezedrying. Stock solutions, varying from very low concentrations with 4 gm RbCl reagent dissolved in 100 cc water to saturated solutions with 80 gm reagent in 100 cc water, were sprayed into isopentane at -160°C. The droplet size in the spray was varied from relatively large 4-mm diameter droplets to extremely small droplets in an aerosol spray. It was determined that both the concentration of the stock solution and the droplet size affect the average size and the size distribution of the primary particles formed and the way in which these primary particles are bonded together. Unlike the powders of many less ionic compounds that are produced by freeze-drying, the primary particles in these RbCl powders are crystalline rather than amorphous. Analysis with an x-ray diffractometer with a cold stage indicates that crystallization occurs during the freezing cycle rather than during the sublimation period of the freeze-drying process.
(Y1−x)Ba2Cu3O6+δ (δ≤0.2): Consequences of Doping Tetragonal 123-Type to Induce Superconductivity
Authors: Parise John B. , Gai Pratibha L. , Crawford M. K. , McCarron Eugene M.
Published: March 2011

Substitution of Ca(II) for Y(III) into tetragonal YBa2Cu3O6 has been achieved and a superconducting transition has been observed for a material of nominal composition (Y0.5Ca0.5) Ba2Cu3O6 (Tc (onset) ˜50K) [1]. Observations using high resolution electron microscopy show samples with x < 0.3 consist of a complex mixture, including (Y, Ca) Ba2Cu3O6+δ, YBa2Cu3O6+δ, and BaCuO2. Further, structural refinement using neutron diffraction data provide evidence of a solid solution limit at x ˜ 0.3. A direct analogy can be drawn between superconducting (Y1−xCax)Ba2Cu3O6 (0.1 < x < 0.3) and superconductors of the type (Y1−xCax)Pb2Sr2Cu3O8 and (La2−xM(II)x)CuO4. Substitution of the Ca(II) for Y(III) effectively increases the formal copper oxidation state. The refined structural model is fully consistent with partially oxidized CuO2 sheets separated by linear O-Cu(I)-O units.
Charge Transfer and Bond Lengths in YBa2Cu3−xMxO6+y
Authors: Miceli P. F. , Tarascon J. M. , Greene L. H. , Barboux P. , Jorgensen J. D. , Rhyne J. J. , Neumann D. A.
Published: March 2011

We discuss the effects of doping on the Cu chain sites in YBa2Cu3−xMxO6+y. The relationship between bond lengths obtained from neutron scattering and charge transfer is evaluated in terms of bond valence. In particular, it is concluded that removing an oxygen from the chains transfers one electron to the planes.
Anisotropy in Normal and Superconducting Properties of Single Crystalline (La1−xSrx)2CuO4
Authors: Kitazawa K. , Kambe S. , Fukuoka A. , Naito M. , Tanaka I. , Kojima H.
Published: March 2011

Transport measurements were made on single crystals of (La1−xSrx)2CuO4 (x = 0.06 and 0.07) which have sizes large enough so that resistivity could be measured reliably along the c-axis by the usual 4 probe method. It was found that conduction along the c-axis was semiconductive in the low temperature orthorhombic structural region, while it was metallic in the high temperature tetragonal region. The resistivity in the basal plane, however, was not affected by the structural phase transition but could be fitted by the T1.3 dependence over the whole temperature range below 300K. The resistive superconducting transition was found to spread significantly under a magnetic field along the c-axis. But the degree of the spreading was essentially independent of the direction of the measurement current. The results suggest that LSCO is a typical 2D metal but with an unusual conduction mechanism and that its superconducting transition is overwhelmed by critical fluctuation under a magnetic field.
Photoemission Spectroscopy of Single Crystal HTSC Materials: A Fermi Liquid Electronic Structure
Authors: Arko A. J. , List R. S. , Bartlett R. J. , Cheong S. W. , Olson C. G. , Yang A. -B. , Liu R. , Gu C. , Veal B. W. , Liu J. Z. , Paulikas A. P. , Vandervoort K. , Claus H. , Campuzano J. C.
Published: March 2011

Photoemission spectra from HTSC materials ( primarily 123 -type ), cleaved and measured at 20K, reveal a rich DOS structure which compares favorably with a calculated band structure, except for a residual 0.5 eV shift which may reflect some correlation effects. Band dispersion is observed throughout the valence bands, with clear evidence for a 0.2 eV wide band dispersing through EF. The orbital character at EF is a mix of Cu-3d and O-2p. There is unambiguous evidence for a large BCS-like gap (2Δ≥ 4kTc).
Electronic Picture in the Normal States of High-Tc Superconductors: From the Optical Viewpoint
Authors: Tajima S.
Published: March 2011

The specific features of the optical spectra in the high-Tc Cu-oxides are discussed. The low-frequency spectral behavior can be explained by the highly correlated electronic model, whereas in the high-frequency spectrum the behavior of the Fermi liquid metal shows up.
Structure, Composition and Superconductivity of High Tc Tl–Ba–Ca–Cu–O System
Authors: Syono Yasuhiko , Kikuchi Masae , Nakajima Satoru , Suzuki Teruo , Oku Takeo , Hiraga Kenji , Kobayashi Norio , Iwasaki Hideo , Muto Yoshio
Published: March 2011

Bulk high Tc superconductors of Tl2Ba2Can−1CunO2n+4 (n=1−4) and TlBa2Can−1CunO2n+3 (n=2−5) were synthesized, and their structures, chemical compositions and superconducting properties were studied by means of X-ray powder diffraction, electron probe microanalysis, transmission electron microscopy, and electrical and magnetic measurements. Superconducting critical temperatures are discussed in terms of average Cu valence and Cu-O bond length within the plane which vary with the number of Cu layers.
Relations Between Structure and Tc In 123,124 and Thallium Oxide Superconductors
Authors: Hewat A.W. , Hewat E.A. , Bordet P. , Capponi J.J. , Chaillout C. , Chene-vas J. , Hodeau J-L. , Marezio M.
Published: March 2011

Small structural changes accompany important changes in Tc in some materials. In YBa2Cu3O6+x, Cava et al. have shown that oxidation to YBa2Cu3O7 involves a significant shift of the oxygen bridging CuO-chains and CuO-planes toward the latter. In YBa2Cu4O8, Kaldis et al. have shown that a similar effect is produced with pressure alone. In both cases, Tc increases strongly. In TI2Ba2Cu1O6, Tc varies greatly depending on the precise method of preparation, though the stoechiometry appears unchanged. In this case, Tc may depend on subtle differences in oxygen content, and perhaps Cu-O bond lengths. These effects can be discussed in terms of charge transfer between intercalated layers of CuO-chains or TIO-planes, and conducting CuO-planes.
Preparation and Characterization of Several Conducting Transition Metal Oxides
Authors: Wold Aaron , Dwight Kirby
Published: March 2011

The structure-property relationships of several conducting transition metal oxides, as well as their preparative methods, are presented in this paper. The importance of preparing homogeneous phases with precisely known stoichiometry is emphasized. A comparison is also made of the various techniques used to prepare both polycrystalline and single crystal samples. For transition metal oxides, the metallic properties are discussed either in terms of metal-metal distances which are short enough to result in metallic behavior, or in terms of the formation of a П*conduction band resulting from covalent metal-oxygen interactions. Metallic behavior is observed when the conduction bands are populated with either electrons or holes. The concentration of these carriers can be affected by either cation or anion substitutions. The discussion in this presentation will be limited to the elements Re, Ti, V, Cr, Mo, and Cu.
Short-Range Ordering by Displacement of Tl and O Atoms in Tl2CaBa2cu2O8 Studied by Pair Distribution Function and Rietveld Analysis
Authors: Toby B. H. , Dmowskia W. , Egami T. , Jorgensen J. D. , Subramanian M. A. , Gopalakrishnan J. , Sleight A. W.
Published: March 2011

Atomic pair distribution function analysis has demonstrated displacements of Tl and O atoms within the Tl-O layers with shortrange ordering of lower symmetry than the crystallographic lattice. Two models have been proposed for these displacements. Rietveld analysis neither confirms nor contradicts these models. Temperature-dependent PDF measurements show changes in local structure correlating with temperature.
Hole Conductors and Superconductors
Authors: Hirsch J.E.
Published: March 2011

A fundamental asymmetry exists between electrons and holes in solids. Electrons at the Fermi surface give rise to high conductivity and normal metallic behavior, holes at the Fermi surface yield poor conductivity and give rise to superconductivity. We review here the theoretical basis for this assertion and its implications, particularly for the understanding of high temperature superconductivity in oxides.
Evidence for Phonon-Mediated Coupling in Superconducting Ba0.6K0.4BiO3
Authors: Hinks D. G. , Dabrowski B. , Richards D. R. , Jorgensen J. D. , Pei Shiyou , Zasadzinski J. F.
Published: March 2011

Superconducting Ba0.6K0.4BiO3, with a Tc of 30K, shows a large 18O isotope effect which indicates that phonons are involved in the pairing mechanism. Infrared reflectivity measurements indicate a value for the superconducting gap consistent with moderate coupling (2Δ/kTc = 3.5 ± 0.5). A mediating energy for pairing of about 40 meV would be required to obtain a Tc of 30K. Strong coupling of electrons by optical phonons (which are present in this material with energies up to 80 meV) could account for the observed transition temperature. Recent tunneling spectroscopy shows the presence of strongly coupled optical phonons in the 40 to 70 meV region, indicating that superconductivity in this material may be phonon mediated.
Ordered Oxygen Arrangements in Y1Ba2Cu3O7−x
Authors: Beyers R. , Ahn B.T. , Gorman G. , Lee V.Y. , Parkin S.S.P. , Ramirez M.L. , Roche K.P. , Vazquez J.E. , Gür T.M. , Huggins R.A.
Published: March 2011

We describe the ordered oxygen arrangements in Y1Ba2Cu3O7−x samples prepared in precisely controlled oxygen environments using a solid-state ionic tehnique. The so-called “Ortho II”phase, characterized by a 〈1/200〉 superlattice wave vector, exists at oxygen contents from 6.28 to 6.65, with electrical properties that range from insulating to superconducting at up to 60 K. Additional ordered structures occur at oxygen contents from 6.65 to 6.90. All of the ordered structures are consistent with the removal of entire chains of oxygen along the b axis, which minimizes the number of three-fold coordinated copper and creates Cu+1 ions even in oxygen-rich samples. We found no evidence for phase separation between 6.0 and 7.0 or between 6.5 and 7.0. Phase separation, if it occurs at all, occurs on the 60 K and 90 K plateaus.
Ion-Beam Induced Epitaxial Crystallization of GexSi1–x/Si Heterostructures
Authors: Elliman R.G. , Ridgway M.C. , Williams. J.S.
Published: March 2011

Amorphous GexSi1–x layers are shown to crystallize epitaxially from an underlying (100) oriented Si substrate when irradiated with 1.5 MeV Ne ions at temperatures as a low as 275°C. For a given Ne fluence, the extent of crystallization is shown to increase with increasing Ge content, consistent with the increased defect production rate in these alloys. It has also been demonstrated that strained layer configurations can be grown by ion-beam annealing and that such layers exhibit a commensurate to incommensurate transformation within the same composition range as layers grown by molecular beam epitaxy.
Amorphous to Polycrystal Transition Assisted by Ion Beam Irradiation in Silicon
Authors: Spinella C. , Lombardo S. , Campisano S. U.
Published: March 2011

The ion beam induced growth of isolated silicon grains has been studied in chemical vapor deposited amorphous layers. The crystal radius increases linearly with the 1on dose and the growth rate depends in a complex way on the irradiation temperature in the 320 - 480 °C investigated temperature range. The grain density does not depend on the ion dose but it increases exponentially with increasing irradiation temperature. The grain density obtained after a pure thermal process on similar samples is In any case larger than the density appearing after ion irradiation. These facts may be explained by assuming that during ion irradiation only pre-existing seeds whose size is larger than a critical value can grow. This critical cluster size is larger than the critical cluster size for a pure thermal process.
Effect of Oxygen Implantation Conditions on Buried Si02 Layer Formation using a Multiple Step Process
Authors: Namavar F. , Cortesi E. , Pinizzotto R.F. , Yang H.
Published: March 2011

We have studied the effect of implantation temperature, dose step, and total dose on the buried Si02 layer formed with a multiple low dose oxygen implantation process. Furthermore, we have produced a continuous, high quality buried SiO2 layer about 1500 Å thick with a dose of only 7 × 1017 0+/cm2 at 160 keV. The thin SiO2 layer is important not only because of the possible economic advantages of reduced dose, but also because a thinner oxide layer is more radiation hard.
Silicon Oxide Film Formation by the Simultaneous use of a Microwave Ion Source and an Icb System
Authors: Takaoka Gikan H. , Tsuji Hiroshi , Ishikawa Junzo
Published: March 2011

SiO2 films were prepared at a substrate temperature of 100°C by the simultaneous use of a microwave ion source and an ICB system. Transparent and good insulating SiO2 films could be obtained by using 02 gas ions, and they were thermally and chemically stable. Furthermore, both the ionization energy and the incident energy of the 02 gas ions were found to enhance the chemical reaction between SiO and 02 molecules, resulting in the Si02 film formation at a low substrate temperature.
Zirconium Nitride Films formed by Dynamic Ion Implantation
Authors: Oppenheim I. C. , Padmanabhan K.R.
Published: March 2011

RF sputter deposition of 500 nm thick zirconium films was carried on simultaneously with implantation of singly ionized molecular nitrogen. Samples were prepared at room temperature (23°C) with a nitrogen to zirconium arrival ratio varying from 2.7x10-2 to 4.4x10-1 and with the ion energy varying from 100 to 300 keV.

Stoichiometry of the films and ion concentration profiles were determined by Rutherford Backscattering Spectrometry. Results from a theoretical model for the ion concentration profiles were compared to profiles derived from experiments. Grazing Angle X-Ray Diffraction was used to correlate nitride phase formation to processing parameters.

Knoop microhardnesses of films deposited on 304 stainless steel substrates were determined. The relative microhardness of the samples were studied as a function of parameters such as film stoichiometry and ion implantation energy.
Observation of Pulsed Laser – Induced Melting of Solid Surfaces by Optical Spin Orientation
Authors: Vaterlaus A. , Lutz M. , Guarisco D. , Aeschlimann M. , Stampanoni M. , Meier F.
Published: March 2011

The optically induced spin polarization P of the photoelectrons emitted from tin and germanium during ps and ns laser pulses is measured as a function of the pulse energy. P is defined by the lattice symmetry of the sample. It vanishes for amorphous or molten surfaces. The melting of the metal and the semiconductor is found to occur on a time scale which is short compared to the duration of a 70 ps laser pulse. The emission of positive ions starts at the laser intensity for which the drop of the polarization is observed. If Ge is heated with ns laser pulses a temperature dependent shift of the work function causes a decrease of the spin polarization for laser energies far below the energy necessary for melting. With ps laser pulses the polarization only vanishes for pulse energies exceeding Eion- The difference between the ps and ns measurements on Ge points to an unexpected dynamical behavior of the work function shift in semiconductors.
TemperatÜRe Measurement by Infrared Transmission for Rapid Thermal Processing Applications
Authors: Sturm J.C. , Schwartz P.V. , Garone P.M.
Published: March 2011

We report a new non-invasive optical technique for the measurement of the absolute temperature of silicon wafers in a rapid thermal processing environment. The method is based on the temperature dependence of the infrared absorption of silicon. Unlike pyrometry, the method can be used with a quartz processing chamber, and it is well-suited to the temperature range of 400 °C to 800 °C. Temperature resolution on the order of one degree can be achieved, and the method can easily be applied to homoepitaxial and certain heteroepitaxial growth cycles.
The Effects of Annealing on the Structure and Distribution of Charge States of Iron Implanted into A-Al2O, at 77 K
Authors: Mchargue C. J. , Sklad P. S. , Mccallum J. C. , White C. W. , Mccallum J. C. , White C.W. , Perez A. , Marest G.
Published: March 2011

Implantation of iron Into α-Al2O3 at 77 K produces an amorphous state for fluences greater than about 3 × 1016 Fe/cm2. Iron in the as-implanted (amorphous) specimens is distributed among two Fe2+, two Fe4+, and the Fe° states. The conversion electron Mössbauer (CEMS) spectra for a sample containing 7 × 1016 Fe/cm2 show all iron to be converted to Fe3+ after annealing in oxygen for 1 h at 700°C and above. The transmission electron microscopy (TEM) shows the structure to be mostly Y-A120, after the 900°C anneal and all α-Al2O, after the 1100°C anneal.
Investigation on mechanisms for ion Beam Induced Degradation of Polyimide
Authors: Xu X.L. , Zuyao Zhou , Lizhi Chen , Shichang Zou
Published: March 2011

Three types of ions with different atomic masses (B , Ar and As ) were chosen to irradiate polyimide films in similar conditions in order to check mechanisms of the formation of ion beam induced damage in polyimide. A four-point probe technique was used to measure sheet resistivities of implanted films. An ion mass effect on conductivity of ion irradiated polyimide film was discovered. The ion mass effect on ion beam induced change of conductivity and on the energy loss process of the ions in polyimide suggest that the electronic energy loss of incident ions is an important factor for the increase of conductivity of implanted polyimide, and the contributions of recoil ionization are restricted by the grave damages as a result of nuclear energy loss process of ions in targets. Our hypothesis is supported by automatic spreading resistance measurement of B implanted polyimide film coated on silicon substrate. The results of this work have been compared with the hypothesis of degradation through direct knock on of atoms in polyimide, proposed by D.Fink et al [Nucl. Instr. and Meths B32 (1988) 125]
Thermal Annealing Investigation of the Optical Properties of BxN1-X Films Fabricated by Ion Beam Assisted Deposition and Application for an Optical Filter
Authors: Carosella C.A. , Donovan E.P. , Hubler G.K. , Skowronek A.E.
Published: March 2011

The annealing behavior of the optical properties of boron nitride films (BxN1-x) is described for films fabricated by ion beam assisted deposition. The data are needed for the precise manufacture of optical filters, where the index of refraction must be predicted from deposition parameters and film annealing history.

The reflection of homogeneous samples deposited at room temperature on (100) silicon substrates was measured from 400 to 3125 nm. to obtain the wavelength dependence of the index of refraction as a function of film nitrogen content. Nitrogen atom fraction was varied from 0.325 to 0.5 by variation of the incident of nitrogen ion beam current to evaporant boron flux ratio. The films were annealed in argon at 500 C and 700 C, and the optical measurements repeated after each anneal. The index of refraction obtained for the annealed films was used to design a narrow band optical reflection filter at 1060 nm. The filter, constructed by sinusoidally varying the index of refraction of the BxN1-x film by varying ‘x’, performed as designed.
Effect of γ-Radiation on Physico-Chemical Properties of Lanthanum Cobaltate (LaCoO3)
Authors: Srinivas B. , Rao V.R.S. , Kuriacose J.C.
Published: March 2011

The influence of γ-radiation on LaCoO3, for the catalytic decomposition of H2O2 has been studied. ESR and XPS studies of γ-irradiated LaCoO3, snowed, the formation of chemisorbed oxygen (O2) and reduction of Co2+ to Co . γ-irradia]:ion of LaCoO3. causes a decrease in electrical conductivity due to the trapping of charge carriers by the chemisorbed oxygen. SEM photographs of the Y-irradiated sample pellets reveal surface cracks and surface corrosion due to the diffusion of transition metal to surface. The enhancement in the catalytic activity for the decomposition of H2O2 is found to be directly proportional to the reduced metal content.
Effects of Ion Beam Bombardment on the Crystalline Structure of Polymers: The Case of Pet+
Authors: Prppleo R.M. , Rrrujo M.R. , Livi R.P.
Published: March 2011

We discuss the amorphization process of semicrystalline and oriented PET (Polytethyleneterephtal ate)) thin toils by ion beam irradiation. P decrease in the bombarded samples melting point and enthalpy of fusion in the bombarded samples, as analysed by Differential Scanning Calorimetry (DSC), is associated with changes in the crystalline morphology and with an increase in the polymer disordered regions. Those facts are confirmed atso by a large decrease in the main X-ray diffraction peak amplitude as the tluence increases. P model of ion induced amorphization originally constructed for metals and semiconductors 11,23 was applied and cross-sections tor the process were obtained. The experimental data are well fitted using this model based on amorphization through the overlap of damage clusters, but an exclusive elastic collisions mechanism for the damage production cannot be inferred. As expected the electronic stopping mechanism also plays an important role in the polymer amorphization process.
Amorphous to Crystalline Phase Transformations in High Dose Ion Implanted Silicon
Authors: Williams J.S. , Thornton R.P. , Elliman R.G. , Li Y.H. , Pogany A.P.
Published: March 2011

Crystallization processes during thermal annealing have been studied for a number of group III, IV and V impurities implanted into amorphous Si. At high impurity concentrations, an amorphous to polycrystalline transformation is observed. For low solubility, low melting point species, this transformation is melt-mediated, whereas it can occur in the solid phase for other species such as Sb.
Stress and Plastic Flow in Silicon During Amorphization by Ion-Bombardment
Authors: Volkert Cynthia A.
Published: March 2011

The in-plane stress in silicon wafers during amorphization by ion-bombardment was determined from wafer curvature measurements using an in-situ laser scanning technique. Measurements were made during room temperature bombardment with 2 MeV Ne, Si, Ar, Kr, and Xe ions. In all experiments, compressive stress was built-up in the bombarded region as a function of the fluence, until a maximum was reached at the dose required to form amorphous silicon. During further amorphization by bombardment, the stress decreased and eventually stabilized. If ion bombardment was interrupted during amorphization, a stress increase was observed over a period of several minutes; when the beam was turned on again, the stress returned immediately to the value measured before interruption. Step height measurements were performed on implanted wafers to determine the out-of-plane strain, and RBS was used to determine the damage profiles. A model is proposed that describes the behavior in terms of the expansion of crystalline silicon by the creation of defects and the flow of amorphous silicon under the ion beam.
Gettering of Cu at Buried Damage Layers Made by Si Self Implantation
Authors: Liefting J.R. , Schreutelkamp R.J. , Lu W.X. , Saris F.W.
Published: March 2011

Channeled implants have been performed with lOOkeV 28Si+ into p-type Si(100) to obtain a buried amorphous layer. Before and after recrystallization of the a-Si layer, Cu was implanted at an energy of 15 keV and a dose ranging from 5E13 to 1E15 I cm2- to obtain a high concentration of Cu in the near surface region. Also, Cu implants were performed into virgin Si for comparison. After Cu implantation, thermal annealing was performed at temperatures between 490 °C and 900 °C for 10 min. to 320 min. Cu profiles before and after annealing were studied with Rutherford Backscattering Spectrometry and channeling analysis. For the case where Cu was implanted after recrystallization of the buried amorphous layer, Cu was gettered at the position where the ale interfaces met during recrystallization. For the case where Cu was implanted before recrystallization, Cu diffused towards the buried a-Si region upon annealing and was trapped inside the recrystallizing buried amorphous layer. The results show that buried damage layers can effectively getter Cufrom the Si surface layer and gettering is most efficient at 600 °C.
Kinetics and Microstructure of Transiently Annealed Implanted Polycrystalline Silicon Layers
Authors: England J.M.C. , Timans P.J. , Mcmahon R.A. , Ahmed H. , Hill C. , Augustus P.D. , Boys D.R.
Published: March 2011

Microstructural changes occurring during the early stages of rapid thermal annealing of polycrystalline silicon bipolar emitters crucially affect the final dopant distribution and hence the performance of these devices. The first stage of annealing is epitaxial regrowth in the solid phase of the layer amorphised by the implantation. In-situ studies using time-resolved reflectivity measurements, combined with cross-sectional transmission electron microscopy of partly annealed structures, have determined the effects of initial grain size, annealing temperature and amorphising species (Si or As) on the rate of regrowth and the microstructural changes which occur during annealing. As the grain size is reduced, the regrowth rate decreases and the interface roughness increases. Arsenic implantation alters the rate of regrowth in such a manner as to produce a smoother interface than that in silicon implanted material.
Effects of Ion Dose on the Morphology and Crystallization of Amorphous Germanium
Authors: Wang L.M. , Birtcherand R.C. , Rehn L.E.
Published: March 2011

1.5 MeV Kr+ irradiation of polycrystalline Ge at room temperature, and subsequent annealing were carried out with in situ TEM observations. After a Kr+ dose of 1.2x1014 ions/cm2, Ge in the electron transparent region was completely amorphized. Continuous irradiation of the amorphized Ge resulted in a high density of small cavities. These cavities, first observed after 7x1014 ions/cm2 with an average diameter of ∼3 nm, grew into large (∼50 nm) irregular-shaped holes, transforming the irradiated Ge into a sponge-like material after 8.5x1015 ions/cm2. The crystallization temperature and the morphology of the crystallized Ge after annealing were found to be dependent on the Kr+ dose. The sponge-like structure was retained after crystallization at ∼600°C.
X-Ray and Raman Topographic Studies of Gaas Implanted With 28Si+ and Pulsed Laser Annealed
Authors: Bowman R.C. , Knudsen J.F. , Adams P.M. , Yao H.D. , Compaan A.D.
Published: March 2011

Double-crystal x-ray diffraction and topography, along with Raman spectroscopy and topography are used to study lattice reconstruction and carrier activation for pulsed laser annealed Si implanted GaAs. Although lattice strain is essentially eliminated, along with the production of carrier concentrations to about 3×1019 cm.3 at the center of laser annealed spots, incomplete removal of implant induced disorder and little dopant activation are observed in surrounding areas. Correlations of Raman and x-ray topographs suggest that concentric regions of partial melting, but without epitaxial regrowth, occur in the periphery of the laser annealed spots.
Ion Beam Induced Percolation Clustering in Al-Fe-Cu Films
Authors: Shang C.H. , Liu B.X.
Published: March 2011

The cencept of percolation can be applied to describe many phase transition problems(l) and various disordered systems(2). An infinite percolation cluster at percolation threshold (Pc) is one of the most prominent fractal system(3). The fractal structure of the percolation clusters makes it possible to connect the universal exponents in percolation transition and the geometrical scaling quantities, like fractal dimension Df. Increasing interest has recently been attractive to produce and study the ideal two-dimensional (2D) percolation films(4,5), which usually composed of a random mixture of crystalline and amorphous phases'(6). In this paper, we first report the direct observation of a percolation cluster consisting of two amorphous phases induced in thin solid films during crystalline-to-amorphous phase trnasformation by ion irradiation.
Effects of Nitrogen Ion Implantation in 304 Stainless Steel at High Temperatures
Authors: Shrivastava Sadhna , Tarey Ram D. , Bhatnager M.C. , Jain Amttaeh , Chopra K.L.
Published: March 2011

We studied the effect of varying the target temperature (by changing the beam power) on the structure and properties of nitrogen ion implanted 304 stainless steel. With a beam power of 0.1 W/ cm2 the target temperature is restricted to 150°C. After a dose of 3. 5x1017N2+/cm2 the microhardness measured at 10g increases by 15%. With a beam power of 1.1 W/cm2 the target temperature is 500°C. After the same dose as before, the irdcrohardness increase is 40%. Glancing Angle X-ray Diffraction and Auger depth profiling results suggest that the increased hardness is due to the presence of nitrogen in solution as opposed to complete precipitation. A sample deformed by compression formed an enhanced oxide layer during implantation. This oxide layer appears to have a capping action against the out-diffusion of nitrogen.
Selective Area Deposition of Conducting Palladium Films on Polyimide Resins
Authors: Kim Yoon-Gi , Bialy S. , Miller R.W. , Spencer J.T. , Dowben P.A. , Datta Saswati
Published: March 2011

We have demonstrated that the selective area deposition of palladium on polyimide substrates is possible through the U.V. photolysis of (π-allyl)(π-cyclopentadienyl) palladium. This photolytic deposition process did not result in any apparent damage to either the Ultem 1000 (polyetherimide) or Kapton substrates (polyimide substrates). The resistivity of the palladium films (< 0.lum) suggests that the films are porous.
Photo-Oxidation of Hydrogenated Amorphous Silicon-Carbon Alloys
Authors: John P. , Odeh I.M. , Qayyum A. , Wilson J.I.B.
Published: March 2011

Hydrogenated amorphous silicon-carbon alloys, a-Si:C:H, have been deposited as thin films (d=0.1-0.5 micron) on crystalline silicon substrates from a capacitively coupled rf discharge in silane-propane mixtures. Variations in the stoichiometry of the films were achieved by altering the ratio of SiH4 to C3H8 flow rates at a sbstrate temperature in the range 240-260°C and total pressure between 30-70 mtorr. The silicon to carbon ratios were established by X-ray photoelectron spectroscopy, XPS, and the hydrogen content and distribution by infra-red spectroscopy.
Patterning of Gaas/AIGaAs Wafers by Focused Electron-Bear Induced Chlorine Etching and Subsequent Kbe Growth
Authors: Taneya M. , Sugimoto Y. , Hidaka H. , Akita K.
Published: March 2011

In-situ patterning of AlxGa1-xAs (0≦x≦0.7) using a electron-beam (EB) and chlorine gas (Cl2) and the application to “In-Situ EB Lithography” are investigated. In this patterning method, an ultra-thin GaAs oxide is utilized as a resist film. The oxide resist prevents C12 gas etching of the underlying material and can be also patterned by an EB irradiation under a C12 pressure, which brings about selective etching of GaAs/AlGaAs layers. Etch rates of AlxGa1-xAs (0<x≦0.7) are 20-30 nm/min, which is almost equal to that of GaAs (20 nm/min). Using this technique of EB-induced patterning, a novel concept “In-Situ EB Lithography” is proposed, where the whole processes for EB lithography are successively conducted in a ultra-high vacuum multi-chamber system. An overgrown layer on a GaAs surface patterned by this “In-Situ EB Lithography” shows a good morphology.
Deep Structures Produced in III-V Materials by Combined Focused Ion Beam Irradiation and Dry Etching
Authors: Harriott L.R. , Wang Y.L. , Chin B.H. , Temkin H.
Published: March 2011

We have developed a direct patterning process for InP based materials which uses ion exposure followed by dry etching to produce surface topography. The substrate is first implanted with a 20 keV Ga+ beam focused to 0.2 micron diameter. The surface pattern is then developed in the substrate by etching with or without a low energy (25 -100 eV) flood Ar+ ion beam in a C12(5×10-4 Torr) atmosphere at 180 to 2000 C. This process has been integrated in a common vacuum chamber with a gas source molecular beam epitaxy (GSMBE) system. In-situ patterning and high quality overgrowth has been demonstrated for low Ar+ ion energies during etching. In this paper, we will describe a model for the patterning mechanism and suggest how it may be exploited to achieve a complete vacuum lithography process compatible with epitaxial regrowth.
Nanosecond Thermal Processing for Ultra-High-Speed Device Technology
Authors: Sigmon Thomas W. , McCarthy Anthony M. , Weiner CA Kurt H. , Carey Paul G.
Published: March 2011

Progress in high-speed device technology is occurring by both scaling of conventional devices, such as MOSFETs and bipolars, and the development of new device structures which take advantage of multi-layer heterostructures. As scaling in lateral dimensions allows production of devices with dimensions approaching 0.lμm, vertical scaling has become a topic of concern. In this paper we focus on nanosecond thermal processing (NTP), anew area of process technology which uses a pulsed uv-laser to perform selective doping and epitaxy on nanosecond time scales. The rapid thermal cycles and precise control of impurity profiles inherent to the new technique addresses many of the problems faced in vertical scaling for silicon MOS and bipolar structures and in the fabrication of selective heteroepitaxial layers. Following a brief historical overview and description of the process, successful applications in the fabrication of submicron MOSFETs and narrow base bipolar transistors in silicon will be presented. Structural and electrical results will be presented for heteroepitaxial layers fabricated in the GexSi1-x and InxGa1-xAs material systems by the technique.
Selective Surface Modification of Fluorocarbon Resin Using Excimer Laser
Authors: Okoshi M. , Murahara M. , Toyoda K.
Published: March 2011

The fluorocarbon resin (Teflon) which is a very stable material chemically, has chemical resistance. Because of this property, it has no affinity for oil or water. Therefore, we have tried selective area modification of the resin surface b-y using an excimer laser.

Fluorocarbon resin is a polymer of C-F bonds. In our experiment, the resin surface was irradiated by an ArF excimer laser, of which the photon energy is higher than that of the C-F bond, to excite the strong C-F bonds. B radicals, the best combination for F atoms, were formed simultaneously. Consequently, F atoms of C-F bonds were pulled out by B radicals. B(CH3 )3 with absorption in agreement with the wavelength of the ArF laser were used as raw materials of the B radicals. By irradiating the gas by the ArF laser beam, the photodecomposed B radicals functioned by pulling out F atoms, and the other methyl radicals ( -CH3 ) substituted for F atoms. As the result, this resin surface turned out to be oleophilic exclusively on the areas exposed to the light.
Elevated Temperature Reactive Ion Etching of GaAs and AIGaAs in C2H6 / H2
Authors: Pearton S. J. , Hobson W. S. , Jones K. S.
Published: March 2011

The temperature dependence of etch rate, surface morphology and atomic composition, and depth of hydrogen passivation of Si dopants in n-type GaAs and AIGaAs has been measured for reactive ion etching in C2H6 /H2. The etching of GaAs shows an increase of a factor of two between 150 and 250°C, decreasing at higher temperatures, while there is no temperature dependence for the etch rate of AlGaAs over the range 50-350°C. The As-to-Ga ratio in the nearsurface region of GaAs remains unchanged over the whole temperature range investigated and there is no polymer deposition. The etched surface morphology is smooth for both GaAs and AIGaAs for all temperatures while the depth of Si dopant passivation by hydrogen shows an increase with increasing substrate temperature during the etching treatment.
Laser Patterning and Electrical Properties of Submicron Lines of Y-Ba-Cu-O
Authors: Zheng J. P , Ying Q. Y. , Kim H. S. , Bhattacharya D. , Shaw D. T. , Kwok H.S.
Published: March 2011

0.6 µm-wide lines of high Tc Y-Ba-Cu-O have been fabricated by direct laser writing on mirror-like thin films which were grown by laser deposition without post annealing. Laser ablation etching had no effect on the Tc and Jc until the lines were < 1µm wide. The 0.6 µm-wide strip showed some degradation of Tc and Jc. The critical current densities for these patterned lines were measured to be ∼5×106 A/cm2 at 50 K.
Laser Induced Chemical Vapor Deposition of GaN
Authors: Kobayashi A. , Asai T. , Kawai S. , Chong P.J.
Published: March 2011

Thin films of GaN were grown on the Al2O3 (0001) substrate by the laserinduced chemical vapor deposition technique. Morphology were different for the films grown with and without laser irradiation. Moreover, the density of nucleus and the growth rate in the case of the growth with the parallel irradiation were greater than those without irradiation. Differences were attributed to presence of photo-dissociated species in the case of the laser irradiation. Additional irradiation normal to the substrate decreased the rate, probably because of the accelerated desorption of the reactive adsorbed species.
Ordering and Energetics of Hg Overlayers on Cu(O01)
Authors: Hutchings C.W. , Dowben P.A. , Kime Y.J. , Li W. , Karimi M. , Moses C. , Vidali G.
Published: March 2011

The growth, ordering, and energetics of Hg overlayers on Cu(O01) have been studied using atom beam scattering, LEED and angle-resolved photoemission. Two stable ordered phases have been identified: one phase is a c(2↑2) and the other phase is a higher density square lattice which has a coincidence c(4↑4) structure. A phase diagram has been determined using LEED and atom beam diffraction data for surface temperatures between 180 and 330 K. ABS data suggest out that there is a narrow coexistance region between these two phases. The isosteric heat of adsorption has been determined as a function of coverage.
In-Situ Transmission Electron Microscopy Studies of the Oxidation of Si (111) 7X7
Authors: Gibson J.M.
Published: March 2011

The kinematical approximation is valid for High-Energy Transmission Electron Diffraction from monolayers in planview. We use this fact to study quantitatively the attack of Si (111) 7×7 by 02. Oxygen is found to bind in the bridging position of the adatom backbonds and render the structure very stable during subsequent 02 exposure. Electron-beam exposure during dosing additionally creates rapid disordering which is presumed to represent SiOx formation.
The Use of Fresnel Contrast to Study the Initial Stages of The in situ Oxidation of Silicon
Authors: Ross Frances M. , Gibson J. Murray , Stobbs W. M.
Published: March 2011

We describe the analysis of Fresnel contrast seen at a free silicon surface in order to characterise the initial clean surface and the formation in situ of the first atomic layers of oxide.
Temperature Dependent Current-Voltage Characteristics in Thin SiO2 Films
Authors: Zhao Jin , Ravindra N. M.
Published: March 2011

An analysis of the Fowler-Nordheim tunneling (FNT) theory and its application to temperature dependent current-voltage characteristics, of very thin films of SiO2 on silicon, is presented. The final results are believed to provide the most complete examination of FN emission theory and predict the breakdown electric field in thin SiO2 films. The role of the roughness, at the Si-SiO2 interface, in determining the FNT current in these structures is also discussed.
Adsorption and Tribochemical Reactions
Authors: Mullins W. M. , Fischer T. E.
Published: March 2011

A model for chemisorption based on the Lewis theory is proposed and developed. The model reproduces the observed relationship between aqueous solubility and band gap for covalent oxides. A relationship is shown between the calculated free-energy of the surface reactions and the observed effect of water on the wear of these materials. This relationship is explained in terms of surface reaction rate and equilibrium. Similar calculations for the adsorption of -CH3functional groups are presented. The results are compared to water adsorption calculations and related to experimental wear test results for model fluids on covalent oxides. The effect of water on lubricant adsorption is discussed.
Atomically-Resolved Surface Photovoltage Probed by Optically-Excited Scanning Tunneling Microscopy
Authors: Hamers R.J. , Markert K.
Published: March 2011

Scanning Tunneling Microscopy combined with optical excitation techniques is used to study non-equilibrium electronic properties of clean silicon surfaces with high spatial resolution. Tunneling potentiometry is performed to measure the excess carrier distributions via the surface photovoltage effect. Well-ordered regions of Si(111)-(7×7) show a uniform surface photovoltage effect, while strong decreases are observed near defects. The decreases in the photovoltage are attributed to an increase in the rate of recombination of electron-hole pairs in the vicinity of the defects.
Topography of Si(111): Clean Surface Preparation and Silicon Molecular Beam Epitaxy
Authors: Tung R. T. , Schrey F. , Eaglesham D. J.
Published: March 2011

Line defects at the interfaces of epitaxial silicide layers grown at room temperature on Si(111) are found to correspond to steps on the original surface. This has enabled the examination, by transmission electron microscopy, of the topography of large areas of the Si surface after various treatments. Methods for removal of surface oxide and carbide are compared. Silicon molecular beam epitaxy (MBE) is shown to occur via step-flow mechanism at high temperatures, and through nucleation and growth of islands on terraces at low temperatures.
Electronic and Atomic Properties of a-C:H/Semiconductor Interfaces
Authors: Wittmer M. , Ugolini D. , Oelhafen P.
Published: March 2011

We have investigated the electronic and atomic properties of the interface between amorphous hydrogenated carbon (a-C:H) films and the semiconductor materials Si, Ge and GaAs with photoelectron spectroscopy, high resolution transmission electron microscopy and ion channeling technique. The different properties of the interfacial layers are summarized and compared to the adhesion quality of a-C:H films on these semiconductor materials.
Non-Equilibrium Molecular Dynamics Simulation of the Rapid Solidification of Metals
Authors: Richardson Cliff F. , Clancy Paulette
Published: March 2011

The ultra-rapid melting and subsequent resolidification of Embedded Atom Method models of the fcc metals copper and gold are followed using a Non-Equilibrium Molecular Dynamics computer simulation method. Results for the resolidification of an exposed (100) face of copper at room temperature are in good agreement with recent experiments using a picosecond laser. At T = 0.5 Tm, the morphology of the solid/liquid interface is shown to be similar to a Lennard-Jones model. The morphology of the crystal-vapor interface at 92% of Tm shows a significant disordering of the topmost layers. Difficulties with the EAM model for gold are observed. Comparison of the Baskes et al. and Oh and Johnson embedding functions are discussed.