bluuebunny/crossref_metadata_2025 huggingface dataset:
Small Lead and Indium Inclusions in Aluminium
Authors: Johnson E. , Hjemsted K. , Schmidt B. , Bourdelle K. K. , Johansen A. , Andersen H. H. , Sarholt-Kristensen L.
Published: March 2011

Ion implantation of lead or indium into aluminium results in spontaneous phase separation and formation of lead or indium precipitates. The precipitates grow in topotactical alignment with the matrix, giving TEM images characterized by moiré fringes. The size and density of the precipitates increase with increasing fluence until coalescence begins to occur. Implantations at elevated temperatures lead to formation of larger precipitates with well developed facets. This is particularly significant for implantations above the bulk melting point of the implanted species. Melting and solidification have been followed by in-situ TEM heating and cooling experiments. Superheating up to ∼ 50 K above the bulk melting point has been observed, and the largest inclusions melt first. Melting is associated with only partial loss of facetting of the largest inclusions. Initial growth of the inclusions occurs by trapping of atoms retained in supersaturated solution. Further growth occurs by coalescence of neighbouring inclusions in the liquid phase. Solidification is accompanied by a strong undercooling ∼ 30 K below the bulk melting point, where the smallest inclusions solidify first. Solidification is characterized by spontaneous restoration of the facets and the topotactical alignment.
Fundamental Aspects of Energetic Collisions Between Clusters of Atoms and Metal Surfaces
Authors: Averback R. S. , Hsieh H.
Published: March 2011

The collision dynamics of Cu, Ni or Al clusters containing 92 atoms with substrates of these same metals were studied using molecular dynamics computer simulations. For energies of 1.0 keV or 326 eV, diverse behavior was observed, depending sensitively on the relative properties of the cluster and substrate. For Cu clusters impacting Cu substrates, the cluster plastically deforms the substrate and creates a deep crater with substrate atoms forming a ridge at the periphery of the crater. In contrast, Al clusters do not much deform Ni substrates, but rather tend to spread epitaxially over the surface. Several Al atoms dissociate from the cluster, and either reflect into the vacuum or scatter over the surface. 326 eV Ni clusters embed themselves almost completely within Al substrates and form localized amorphous zones.
Layer Thickness Dependence of Transport Properties in Y1Ba2Cu3O7-y Superconducting Multilayer Films
Authors: Lee Sang Yeol , Narumi Eiki , Shaw David T.
Published: March 2011

Multilayers of Y1Ba2Cu3O7-y/Y1Ba2(Cu1−xNix)3O7-ysuperconducting thin films have been grown epitaxially on (100) ZrO2 substrates using a pulsed laser deposition technique. The thickness of the Y1Ba2Cu3O7-y layer was varied from 60 Å to 900 Å and the thickness of the Y1Ba2(Cu1−xNix3O7-y layer was varied from 60 A to 100 A to determine the effect of the Ni-doped layers on the superconducting properties. Variations of critical current density were investigated as a function of temperature in magnetic fields up to 5 T. Magnetic field dependence of normalized critical current density, Jc(H)/Jc(O), is improved by the growth of Ni-doped multilayer structures, possibly due to an increase in flux pinning force.
Studies of Critical Current Density Enhancement in (Cax Y1−x)Ba2Cu4O8 (1:2:4)
Authors: Narwankar P. K. , Chandrachood M. R. , Fendorf M. , Morris D. E. , Sinha A. P. B. , Gronsky R.
Published: March 2011

Samples with the stoichiometry (CaxY1−x)Ba2Cu4O8, x = 0, 0.1 were synthesized at P(O2) = 25 and 200 bar. High Resolution TEM images for the samples synthesized at 25 bar show a high density of planar defects as compared to almost defect free microstructure of Ca0.1Y0.9Ba2Cu4O8 synthesized at 200 bar. The intragrain critical current density of the high defect density samples is however about 100 times lower that that of Ca0.1Y0.9Ba2Cu4O8 synthesized at P(O2) = 200 bar.
Weak Pinning Centers in Proton Irradiated YBCO Single Crystals
Authors: Zhao Y. J. , Liu J. R. , Tao Y. K. , Hor P. H. , Chu W. K.
Published: March 2011

Observed magnetic Jc enhancement in a 3.4 MeV proton-irradiated Y1Ba2Cu3O7-δ (YBCO) single crystal are shown to be intimately linked with a kind of weak pinning centers. Applied magnetic field transforms weak centers into the normal state or pinning centers, which then cause pinning enhancement. Strong pinning anisotropy of the radiation induced weak center can be explained very well by the size anisotropy of a superconducting unit cell and a flux line, or the coherence length.
Enhancement of Pinning Energy and Critical Current Density in Tl2CaBa2Cu2O8 Films by Proton Irradiation
Authors: Reeves M. E. , Weaver B. D. , Summers G. P. , Soulen R. J. , Olson W. L. , Eddy M. M. , James T. W. , Smith E. J.
Published: March 2011

Measurements are presented which show the effect of proton irradiation on the irreversibility line and critical current in Tl2 CaBa2Cu2O8 thin films. These data show that the irreversibility line is dependent on the defect structure and that the pinning energy is increased by proton irradiation. This leads to an increase in the critical current density at 60 K for the lowest radiation dose. Further irradiation reduces the critical current, even while the irreversibility line is enhanced.
Ion Beam Assisted Deposition of Cubic Boron Nitride Thin Films
Authors: Kester Daniel J. , Messier Russell
Published: March 2011

Boron nitride thin films were grown using ion beam assisted deposition. Boron metal was evaporated, and the depositing film was bombarded by nitrogen and argon ions. The films were characterized using Fourier transform infrared spectroscopy, electron diffraction, transmission electron microscopy, and Rutherford backscattering. The thin films were found to be cubic boron nitride, consisting of 100–200 Å crystallites with a small amount of an amorphous secondary phase. The best conditions for depositing cubic boron nitride were found to be a substrate temperature of 400°C, bombardment by a 50:50 mixture of argon and nitrogen with a bombarding ion energy of 500 eV and a ratio of bombarding ions to depositing boron atoms of from 1.0 to 1.5 ions per atom.
Derelaxation of Amorphous Silicon by Ion Implantation: Optical Characterization
Authors: Reitano R. , Grimaldi M. G. , Baeri P. , Bellandi E. , Borghesi A. , Baratta G.
Published: March 2011

The transition between relaxed and unrelaxed amorphous silicon can be obtained by thermal treatment of the unrelaxed amorphous or by low dose ion irradiation of the relaxed material. In both cases a variation in the short range order has been invoked to explain the behavior of the structural changes probed by various techniques. In this work we study the influence of such changes on the optical properties of a-Si in the region of the transition between the relaxed and the unrelaxed states. We show that a progressive variation of the optical constant in the visible-near infrared region upon derelaxation occurs. Therefore, significant modifications of the electron density of state in the region above the optical gap are associated with the changes in the short range order probed by Raman spectroscopy.
Hydrogen in Dielectric Film Formation From an Electron Cyclotron Resonance Plasma
Authors: Barbour J. C. , Stein H. J.
Published: March 2011

The incorporation of hydrogen into silicon nitride films grown downstream from an electron cyclotron resonance (ECR) plasma decreased rapidly with increasing substrate temperature (100–600°C). Fourier transform infra-red (FTIR) spectroscopy showed that the hydrogen in the as-grown material was primarily bonded to nitrogen. However, an applied bias of -200 V caused an increase in the number of Si-H bonds relative to N-H bonds, as a result of increased ion-beam damage. In addition, ion irradiation of an as-grown film with 175 keV Ar+ at room temperature showed that H transferred from N-H bonds to Si-H bonds without a loss of H. Elastic recoil detection (ERD) and FTIR of thermally annealed films showed that the stability of H incorporated during deposition increased with deposition temperature, and that the N-H bond was more stable than the Si-H bond above 700°C. Deuterium plasma treatments, at 600°C, of annealed films caused isotopic substitution with a conservation of bonds. Therefore, hydrogen loss from annealed films is apparently accompanied by a reduction in dangling bonds.
Characterization of the Depositing Flux in Laser Ablation Deposition (LAD).
Authors: Kools Jacques C.S. , Dieleman Jan
Published: March 2011

Angular-resolved time-of-flight (ARTOF) studies have been performed on ablation plumes of copper generated by excimer laser fluences just above threshold in vacuum. Positive ions, Rydberg atoms and ground-state neutrals are observed. Relative concentrations, angular intensity distributions and angular-resolved velocity distributions are measured for ground state neutrals and ions.

Ions have the highest kinetic energies ( 20–80 eV). Their angular distribution is isotropic. Their concentration at the substrate is very low ( ≤ 10−6). Ground state neutrals have lower energies ( ≈ 1 eV). Their intensity and velocity is a strongly decreasing function of the polar angle. Rydberg-atoms have energies in between those of ground-state neutrals and ions. Their angular distribution is also dependent on the polar angle.

The concentration, kinetic energy and angular distribution of the ionised species arc very well explained by a mechanism of thermal ionization and subsequent space-charge induced repulsion. The velocity distributions and angular intensity distributions of the ground-state neutrals are quantitatively predicted by a model for the flow dynamics of pulsed laser generated gas clouds.
1N-SITU Ellipsometry Study of Pulsed Laser Deposited ZnO Films
Authors: Pittal Shakil , McConville L. A. , Ianno N. J. , Snyder P. G.
Published: March 2011

Ellipsometry is normally used to characterize layered structures that have uniform properties laterally across the area of the probe beam. In this study, pulsed laser deposition of ZnO films was found to have highly nonuniform growth properties in the lateral directions. We were able to account for the effects of the nonuniform growth on in-situ ellipsometric data, by considering two dynamic growth models.
Effects of Processing Parameters on KrF Excimer Laser Ablation Deposited ZrO2 Films
Authors: Smith Gary A. , Chen Li-Chyong , Chuang Mei-Chen
Published: March 2011

Systematic experiments have been carried out to characterize the yttria containing zirconia thin films on sapphire substrates by 248nm KrF excimer laser ablation. The deposition rate as a function of laser fluence and O2 pressure at room temperature was measured with a quartz crystal microbalance. The results show different threshold fluences for deposition in vacuum vs. oxygen. While the deposition rate increases with increasing fluence at a given oxygen pressure, the rate eventually saturates at a higher laser fluence. At a given fluence, the oxygen pressure dependence of the deposition rate shows a radical reduction when the O2 pressure increases from 10 mTorr to 1 Torr. Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy were used to obtain stoichiometric information. A very strong pressure dependence of the O/Zr ratio was observed. While the trend of increasing O/Zr and Zr/Y ratio with increasing O2 pressure is apparent, the correlations between O/Zr as well as Zr/Y ratio and other processing conditions are less obvious. RBS results indicate an increasing roughness at the interface between the ZrO2 film and the sapphire substrate as the oxygen pressure exceeds 50 mTorr. The structural information obtained from x-ray diffraction patterns indicates broadening of peak width with increasing laser fluence as well as decreasing substrate temperature. For the film deposited at a lower substrate temperature, a strong (002) texture was observed.
Processing of Y1Ba2Cu3O7−x Superconducting Thin Films on GaAs Substrates with Double Buffer Layers
Authors: Lee Sang Yeol , Jia Quanxi , Anderson Wayne A. , Shaw David T.
Published: March 2011

High temperature superconducting Y1Ba2Cu3O7−x(YBCO) thin films have been grown on GaAs substrates by in situ laser deposition with a double buffer layer of yttrium-stabilized ZrO2(YSZ)/Si3N4. A barrier layer using a combination of YSZ/Si3N4 was used to grow high quality YBCO thin films without the degradation of the GaAs during YBCO film deposition. Strongly c-axis oriented superconducting YBCO thin films with a zero resistance temperature of 85.5 K and a critical current density of 1.9×103 A/cm2 at 77 K have been obtained. The electrical properties of the YBCO thin films were mainly dependent on YSZ buffer layer deposition condition.
Pulsed Laser-Induced Amorphization of Silicon Films
Authors: Sameshima T. , Usui S.
Published: March 2011

Amorphization of silicon films occurred through homogeneous solidification of molten silicon layers on quartz substrates induced by irradiation with a 30ns-XeCl excimer laser. The crystalline nucleation rate was obtained to be 8×1030m−3s−1. Silicon films were completely amorphized for films thinner than 18nm. Complete amorphizatoin is brought about by reduced grain size and reduced recalescence as the film thickness decreases. Recalescence was observed in situusing transient thermometry with a platinum-temperature-sensing layer when a 15nm-thick silicon film was amorphized.
Buried Quantum Well Structure Fabricated by in Situ EB Lithography
Authors: Kawanishi H. , Sugimoto Y. , Ishikawa T. , Tanaka N. , Hidaka H.
Published: March 2011

Buried quantum well structures have been fabricated in GaAs/AIGaAs system using an in situ lithography process. The process utilizes an ultrathin oxide layer formed in situ on a GaAs surface as a mask against Cl2 gas etching. An electron beam (EB)-induced Cl2 gas etching is used to locally remove the oxide mask for positive-type lithography. For negativetype lithography, the oxide mask is selectively formed on a GaAs surface by EB-stimulated oxidation. Subsequent Cl2 gas etching results in the formation of isolated quantum wells. After removing the oxide mask, overgrowth using molecular beam epitaxy is successfully carried out on the patterned surface. The cathodoluminescence image of the buried quantum well demonstrates the high quality of the resulting structure formed by this “in situ EB lithography” process. The photoluminescence intensity from the quantum well of the processed sample is proved to be the same order of magnitude compared with that from a successively grown sample, showing that the use of the oxide mask causes no serious degradation in the processed interface.
Condensed Chlorine Etching of GaAs Induced by Excimer Laser Radiation
Authors: Freiler M.B. , Shih Ming Chang , Haase G. , Scarmozzino R. , Osgood R.M.
Published: March 2011

We report excimer laser induced etching of GaAs samples covered with a layer of condensed Cl2. The experiments were performed at low temperatures (120-150 K) and in a chlorine ambient (PC12=1-40 mTorr). Spatially well-resolved, anisotropic etching has been demonstrated with an observed etch rate of 0.25 Å/pulse (0.1 μm/min for typical parameters). The etch rate is characterized as a function of the various system parameters (pressure, temperature, laser rep-rate, etc.), and a model is proposed to describe the etching mechanism.
Electron Beam Induced Decomposition of Palladium Acetate
Authors: Stark T.J. , Mayer T.M. , Russell P.E.
Published: March 2011

A focused electron beam has been used to selectively decompose sub micron thick films of palladium acetate, Pd(OOCCH3)2, resulting in the formation of <0.1μm wide Pd rich features. Resistivity of the palladium acetate film decreased when exposed to doses above 500μC/cm2. Annealing to 160°C further reduces the resistivity of the exposed areas to as low as 100μΔcm. XPS analysis of the exposed areas indicate that the Pd is reduced to a metallic state and that the ratio of C and 0 to Pd drops to 1.5 and 0.6, respectively, after exposure. Residual gas analysis during exposure indicates that CO2 and CH3 are the primary volatile products of the decomposition.
Ablation of Single Crystal MgO by UV Excimer Irradiation
Authors: Webb R. L. , Jensen L. C. , Langford S. C. , Dickinson J. T.
Published: March 2011

The ablation of single crystal MgO irradiated with 248 nm excimer laser light is studied by means of time resolved spectroscopy and quadrupole mass spectrometry. Luminescence spectra and SEM observations indicate that repeated laser bombardment gradually increases the density of potentially absorbing defects. In polished samples, this progressive growth is preceded by an initial clean-up (reduction) of surface damage. Unlike many wide band gap materials, defect production in MgO by electronic mechanisms is not likely. Chemical etch techniques indicate the presence of high dislocation densities in regions etched by the laser, suggesting that point defect production by dislocation motion is important. The ablation plume is composed of charged particles, including cluster ions, as well as a high density of excited neutrals. The growth of the plume with repeated bombardment correlates with defect formation as indicated by luminescence intensities.
Nanostructure Fabrication: Dry Etching Damage
Authors: Doughty G.F. , Cheung R. , Foad M.A. , Rahman M. , Cameron N.I. , Johnson N.P. , Wang P.D. , Wilkinson C.D.W.
Published: March 2011

Although the directed energy and chemical reactivity of dry etching permits the fabrication of nanostructures with precise geometries, it also causes unwanted electrical and optical changes to the surface, changes generally referred to as “damage”.

This paper discusses the extent and the impact of dry-etching damage on rI-V and I[-VI compound semiconductors as assessed by a very wide range of techniques: the performance of devices such as MESFETs, and measurements of other properties - surface uniformly and precisely, Schottky junction characteristics, cut-off of epitaxial wire conductance, integrated photoluminescence, X-ray reflectivity, DLTS, TEM imaging and Raman scattering.

We distinguish an important difference between the nature of damage on sidewalls and on surfaces normal to the directed ions, and report on progress towards establishing a model of the nature of dry etching damage. This model is applied to indicate what kinds of processes are likely to give etching with low damage.
The Synthesis of Metal Oxide Films from Compound Powder Targets
Authors: Stognij A.I. , Tokarev V.V. , Mitin Yu.N.
Published: March 2011

The paper presents the results of AES, SIMS, RBS and electron microscopy investigation of compound metal oxide films. The films were deposited by sputtering compound targets with oxygen ion beam, extracted from hollow cold cathode ion source.
Low Temperature Silicon Epitaxial Growth by Plasma Enhanced Chemical Vapor Deposition from SiH4/He/H2
Authors: Lin Yung-Jen , Shieh Ming-Deng , Lee Chiapying , Yew Tri-Rung
Published: March 2011

Silicon epitaxial growth on silicon wafers were investigated by using plasma enhanced chemical vapor deposition from SiH4/He/H2. The epitaxial layers were growm at temperatures of 350°C or lower. The base pressure of the chamber was greater than 2 × 10−5 Torr. Prior to epitaxial growth, the wafer was in-situ cleaned by H2 baking for 30 min. The epi/substrate interface and epitaxial layers were observed by cross-sectional transmission electron microscopy (XTEM). Finally, the influence of the ex-situ and in-situ cleaning processes on the qualities of the interface and epitaxial layers was discussed in detail.
Low Temperature UV Growth of SiO2 in O2 and N2O
Authors: Kazor Asghar , Boyd Ian W.
Published: March 2011

We report here the use of a low pressure Hg lamp to grow oxide layers on Si in N 2O and O2. Layer thicknesses up to 100Å, whose IR absorption characteristics are similar to those exhibited by thermal oxides, have been produced. Preliminary modelling of the process is described.
Phosphorus and Boron Doping of Silicon Thin Films Using ArF Excimer Laser
Authors: Slaoui A. , Elliq M. , Pattyn H. , Fogarassy E. , Unamuno S. De , Stuck R.
Published: March 2011

This work describes phosphorus (P) and boron (B) doping of polysilicon filns deposited on quartz. Doping is achieved by means of a pulsed ArF excimer laser to melt a controlled thickness of amorphous or polycristalline silicon film coated with a spinon silicate glass (SOG) film containing the dopant (P or B). We have investigated the influence of doping parameters such as laser fluence, number of shots and dopant film thickness on the sheet resistance and the incorporation rate. From these results, we have shown that high doped, shallow junctions presenting sheet resistance lower than 5 kΩ/∠ can be obtained. Poly-Si TFT's with good electrical characteristics were successfully fabricated using this doping technique.
Characterization of High Temperature Superconducting Thin Film Grown by Laser Ablation Method
Authors: Shimizu K. , Nobumasa H. , Nagai N. , Matsunobe T. , Kawai T.
Published: March 2011

We have measured the complex dielectric function of Bi2Sr2CaCu2Oy, samples in the near infrared region directly by spectroellipsometry. As for both single crystal and thin film. superconducting samples have a zero point in the real part (ε1) of the complex dielectric function (ε*) and a clear peak of the imaginary part of the inverse ε* at almost the same frequency. On the other hand, non-superconducting samples have no such ε1, zero point, and the peak height of (-Im(l/ε*)) becomes small. Then we can determine the superconductivity of samples by this spectroellipsometry measurement at room temperature.
Low Temperature Synthesis of Carbide Thin Films by Pulsed Laser Deposition (Pld)
Authors: Donley M.S. , Zabinski J.S. , Sessler W.J. , Dyhouse V.J. , Walck S.D. , McDevitt N.T.
Published: March 2011

Thin films of titanium carbide (TiC) and boron carbide (B4C) were grown by excimer pulsed laser deposition (PLD) at room temperature (RT) and 300°C. Films were deposited using the output of an excimer laser operating with KrF gas (λ = 248 nm, 15 ns pulse duration) to ablate hot-pressed targets. Film chemistry, morphology, and crystallinity were investigated. Stoichiometric, crystalline TiC films were grown on 440C stainless steel and NaCl substrates at room temperature and at 300°C. The films grown on NaCI were nanocrystallinc, cubic TiC, with a grain size ranging between 2 and 10 nm in diameter. Boron carbide films were grown on silicon {100} substrates at room temperature and at 300°C. Film chemistry and stoichiometry duplicated that of the B4C target, which contained B4C and a mixed C-B-O-N binder phase. SEM analysis indicated that the morphology of the films was uniform, nonporous, and fine-grained. The films exhibited good adhesion and wear resistance, based on friction and wear data collected with a ball-on-disc tribometer.
Growth of Bn Thin Films by Pulsed Laser Deposition
Authors: Knapp J. A.
Published: March 2011

A new UHV system for pulsed laser deposition of materials is described, together with results from preliminary experiments for depositions of BN on Si. The system is designed to allow for in-situ diagnostics of the ablation plasma, as well as UHV preparation and characterization of clean sample substrates. The room temperature depositions of BN result in amorphous, B-rich films, whose particle content is a strong function of laser wavelength.
Comparison in Surface Modifications of Sintered and Single Crystal Ceramic Targets After Laser Ablation
Authors: Young K. H.
Published: March 2011

A systematic study of the surface morphology and chemical composition of several ceramic targets after pulsed laser ablation has been conducted using a scanning electron microscope with x-ray energy dispersive spectroscopy. We have examined single crystal LaAIO3 and NdGaO3 disks, as well as powder sintered LaAIO3 and SrTiO3 discs. These targets were rotated during laser ablation and concentric trenches were formed with distinctive surface morphologies due to different doses of laser energy. We observed varied light-solid surface interactions on the targets prepared by different methods. The sintered targets exhibited surface explosions after long period laser ablation, presumably due to sub-surface overheating [1]. The single crystal targets have smoother surface morphology and the resulting films have much fewer particles on the surface. As such, they are preferred for laser ablation applications.
The Growth Kinetics and Shape Evolution of Precipitates Growing by the Ledge Mechanism
Authors: Enomoto Masato , Spanos George , Masumura Robert A.
Published: March 2011

The characteristics of ledge growth of precipitates are investigated by a previously developed finite-difference computer model. The plate lengthening simulation results which incorporate measured ledge heights and spacings are in reasonable agreement with the observed lengthening behavior of plates in Fe-C alloys. The simulation which takes into account the diffusion field interaction among multiple precipitates shows that a variety of precipitate morphologies actually observed can possibly be formed solely by the change in the extent of diffusion field overlap among ledges and/or neighboring precipitates. This overlap is in turn caused by changes in the solute supersaturation, distribution of ledge nucleation sites and ledge nucleation rates. A brief discussion is made of the relative growth kinetics of ledged and disordered interfaces.
Velocity and Morphology Transition in Dendritic Growth
Authors: Raz E. , Chait A.
Published: March 2011

The growth velocity and morphology of crystals growing in a supercooled aqueous solution of ammonium chloride (28 wt%) with small amounts of copper sulfate (0.05 to-1 wt%) have been examined. For the [100] growth direction at low supercooling and for the [110] direction at greater supercooling the crystals start to grow slowly with a faceted interface. As the supercooling is continuously increased, the growth direction becomes [111]. Dendrites with pointed tips develop but continue to grow slowly. With further increase in supercooling, the velocity increases 20- to 40-fold and the tip shape changes from a cusp to a thin and almost paraboloid interface while the growth direction remains [111]. The velocity transition is gradual when the concentration is below 0.1 wt% but is sharper at higher concentrations. The transition temperature decreases with increasing copper sulfate concentration.

We postulate that the observed transition indicates a dynamic roughening phenomenon, where the supercooling; is sufficiently high to create many nucleation islands on the faceted interface. In this case the interface behaves as an atomically rough surface and dendrite growth occurs at an interface temperature that is below the equilibrium temperature.
Growth Properties of the Si(100) Steps: A Molecular Dynamics Study
Authors: Roland Christopher , Gilmer George H.
Published: March 2011

We have mapped out the energy surfaces seen by a single silicon adatom over the Si(100) surface and Si(100) steps, using Molecular Dynamics methods. This identifies the most likely binding sites as well as the activation energies for diffusion over the terraces and steps. We find that only the 5e step with no rebonded atoms is a good sink for adatoms - the SA, rebonded Sb and Db steps are weak sinks. Because of a higher density of binding sites and lower activation energies for surface diffusion along die step edge, we expect mat growth at the Sb and Db steps take place much more readily man at the SA step.
Temperature-Dependent Evolution of Chemisorbed Digermane in Ge Thin Film Growth
Authors: Eres Djula , Sharp J. W.
Published: March 2011

The formation and evolution of chemisorbed digermane layers in context with germanium thin film growth was investigated by time-resolved surface reflectometry. Modulation of the source gas supply made possible the separation and independent study of the temperature dependence of the adsorption and desorption processes. The regeneration of active sites by molecular hydrogen desorption was identified as the rate-limiting step at low substrate temperatures. A dynamic method of thin film growth was demonstrated by repetitively replenishing the active film growth sites regenerated between two successive source gas pulses. The film growth rate was shown to be related to the substrate temperature and the delay time between successive source gas pulses.
Grazing Incidence X-Ray Reflectometry Studies of Cadmium Arachidate Langmuir-Blodgett Films
Authors: Tanner B. K. , Bowen D. K , Petty M. C , Swaminathan S. , Granfeld F.
Published: March 2011

Grazing incidence X-ray reflectometry has been used to characterize Langmuir-Blodgett films of cadmium arachidate deposited on silicon substrates. The agreement between layer parameters deduced from the interference fringe period and low angle Bragg peak positions was excellent. Good agreement was found between experimental and simulated reflectivity profiles only when interface roughness and a varying molecular layer thickness was included. Inclusion of interface roughness alone results in a substantial enhancement in the intensity of the Bragg peaks. This effect is identified as being equivalent to the reduction in extinction found in classical X-ray diffraction due to crystal imperfections.
A Grazing Incidence X-Ray Diffraction Study of Self-Assembled Monolayers
Authors: Fenter P. , Li Jun , Eisenberger p. , Ramanarayanan T. A. , Liang K. S.
Published: March 2011

We describe the two dimensional structure of n-Alkyl Thiols, CH3(CH217SH(C18, self-assembled on the surfaces of Au(111) and Ag(111). By using Grazing Incidence X-ray Diffraction (GIXD), we show that C18 forms ordered and dense monolayers. Although the properties of Au and Ag are very similar (for instance, the lattice constants of Au an Ag are nearly identical), the structure of C18on these two substrates is very different.
Electrochemical and Chemical Sulfidation of GaAs: A Surface Chemical Study
Authors: Yota J. , Burrows V. A.
Published: March 2011

Treatment of gallium arsenide with sulfur-containing media has been shown to improve GaAs surface electronic properties. However, there is still considerable controversy regarding the chemical nature of the surface film which results from the sulfidation, and of the basis of the electronic improvement and of the decay in the improved electronic properties with time. We have investigated the surface chemistry of the chemical sulfidation treatment of GaAs with Na2S-9H2O and the electrochemical sulfidation treatment of GaAs with Na2S-9H2O-ethylene glycol. Using surface infrared spectroscopy (SIRS), we have studied the film formed on the surface after the treatments and its behavior with time. Results show that the film on the GaAs surface contains sulfur which is often associated with oxygen, that this film slowly reacts in air to form unexpected species, e.g. sodium carbonate and sulfur-oxygen group-containing compounds, and that sulfur and oxygen are non-uniformly distributed.
Real-Time Studies of Interface Structural Dynamics
Authors: Lowe Walter P. , Clarke Roy
Published: March 2011

We present dynamic structural studies of thin films and their interface with underlying substrates using real-time x-ray diffraction. Using synchrotron light we have observed, in real-time, interface dynamics in semiconductor systems such as GexSi(i−x)/Si. The measurements show that under large temperature changes thin epitaxial layers may behave cooperatively to modify the overall strain profile. Dynamic behavior is exhibited in a series of discontinuities in the perpendicular lattice constant of the overlayer.
Hydrogen Adsorption Effects on Thin Film Growth Mode Studied by Ion Scattering
Authors: ShojiK F. , Sumitomo K. , Kinoshita T. , Tanaka Y. , Oura K. , Katayama I.
Published: March 2011

The effects of hydrogen adsorption on the growth process and structures of Ag thin films on Si(111)-7×7 surfaces has been studied. The growth process and film structures are investigated by low energy electron diffraction(LEED) and low energy ion scattering spectroscopy of time of flight mode(TOF-ICISS). The hydrogen adsorbed on the surface is investigated by low energy recoil detection analysis(TOF-ERDA). We have found that Ag thin films deposited onto hydrogen covered Si(111) surfaces grow with a mode definitely different from that on clean surfaces.
Change Of SI(111) Surface Reconstruction Under Noble Metal Films
Authors: Hong Hawoong , Aburano Richard , Lin D.-S. , Chiang T.-C. , Chen Haydn , Zschack P. , SPECHT E. D.
Published: March 2011

Interface structures between Si(111) and thick noble metal overlayers are studied by grazing-angle-incidence x-ray diffraction and crystal truncation rods. The 7×7 reconstruction is only preserved under a Ag film deposited at room temperature. This capped 7×7 structure changed to a 1×1 structure upon annealing over 250°C. A thick overlayer of room temperature deposited Au film destroyed the 7×7 reconstruction and changed the interface structure to 1×1. Our results are compared to a thick Cu/Si(111) interface structure1.
Profile Structures of Macromolecular Monolayers on Solid Substrates By X-Ray Interferometry/Holography
Authors: Kent Blasie J. , Xu Sontao , Murphy Margaret , Chupa Janine , McCauley John P. , Smith Amos B. , Petacolas Lawrence J. , Bean John C.
Published: March 2011

Previous work has recently employed x-ray interferometry for the unique determination of the profile structures of ultrathin Langmuir-Blodgett multilayer films of Cd-arachidate and of tethered protein monolayers on the surface of Ge/Si multilayer substrates [1, 2]. These studies utilized the inorganic substrate as the reference structure for the interferometrie phasing of the meridional x-ray diffraction I (Qxy=0A-1, QZ) from the inorganic-organic composite structure. The substrates, fabricated by magnetron sputtering, contained only broad profile features (≥20 A), thereby limiting the spatial resolution of the organic profile structures so-determined. Molecular beam epitaxy (MBE) permits the fabrication of the multilayer reference structure with profile features as narrow as a single atomic monolayer, thereby providing delta-function-like features in the reference structure. The reference structure can then be tailored such that the autocorrelation function of the inorganic-organic composite profile structure [obtained by a Fourier transform of its meridional diffraction I (Qxy=0A-1, Qz) data without phase information] contains only the organic profile structure itself over a particular range of the profile coordinate z. This approach for uniquely determining the unknown profile structure of the organic overlayer is x-ray holography by analogy to simple off-axis holography with much longer wavelength radiation. We have initially utilized MBE fabricated Ge/Si multilayer substrates of the type N(Ge2Si30), e.g., for N=2 or 3 superlattice unit cells, each containing two Ge monolayers and thirty Si monolayers, to thereby determine the profile structures of four different organic overlayers, namely a) self-assembled alkylsiloxane monolayers, b) Langmuir-Blodgett cadmium alkylcarboxylate monolayers, c) a Langmuir-Blodgett Cd-arachidate head-to-head bilayer deposited on a)-above and, d) a covalently tethered protein monolayer.
Ion Channeling Study of Epitaxial Growth of α-Fe on H-Terminated Si (111) Surfaces
Authors: Karmarkar M. M. , Padmanabhan K. R. , Cheng Y.-T. , Chen Y. L.
Published: March 2011

Epitaxial α-Fe films deposited on H-terminated Si(111) surfaces by electron beam evaporation in ultra high vacuum were studied using ion channeling/Rutherford Backscattering spectrometry (RBS). A 700 Å thick Fe film deposited on a Si(1 11) substrate at room temperature has a surface minimum yield, χmin, of 22% at 2 MeV energy of 4He+ ions along Si <111>. A rapidly increasing yield in the aligned spectrum with the depdi of the film shows the presence of defects throughout the film. The sharp lower energy edge of the Fe signal indicates the absence of an amorphous region or a suicide layer at the interface. This establishes epitaxial growth of iron film on Si(111), a result supported by x-ray diffraction and transmission electron microscopy studies. A 700 Å thick iron film deposited at 300 °C shows a surface minimum yield of 12%. Ion channeling/ backscattering spectra of 1400 Å and 3000 Å thick Fe films deposited at 300 °C on Si(111) substrates show a χmin of about 3% for both films, indicating a substantial reduction in the defect density in the thicker Fe films. Etching of Si(111) substrates in either a 10% HF solution or a NH4F solution does not change the crystalline quality of the iron films significantly.
Growth of Au on A Ge (111) Surface
Authors: Dunn D. N. , Xu P. , Marks L. D.
Published: March 2011

We investigate the room temperature growth of evaporated Au thin films on both clean and dirty single crystal Ge (111) substrates. The annealing behavior of these films was then examined under low and high temperatures.
Surface Reconstructions of Strained Epitaxial CoSi2/Si(100) Layers Studied by Scanning Tunneling Microscopy.
Authors: Stalder R. , Schwarz C. , Sirringhaus H. , VON Känel H.
Published: March 2011

Epitaxial single-domain CoSi2(100) layers were grown on Si(100) by use of a template technique. In-situ scanning tunneling microscopy (STM) and reflection high energy electron diffraction (RHEED) were used for a detailed surface study. The (√2×√2)R45 reconstruction of the Co-rich “C-surface” and the (3√2×√2)R45 as well as a newly discovered (√2×√2)R45 of the Si-rich “S-surface” were resolved in real space and are discussed in detail. The transition from the C- to the S-surface above 500 °C is related to a (2×2) reconstruction.
A Novel Growth Method for High Quality GaAs/CaF2/Si(111) Structures by Using “Type-A” CaF2 Film
Authors: Mizukami H. , Ono A. , Tsutsui K. , Furukawa S.
Published: March 2011

Control of epitaxial relationship of CaF2 films grown on Si(111) substrates was considered to be important to improve surface morphology and crystallini ty of GaAs films on CaF2/Si(111) structures. We successfully grew CaF2 films with the “type-A” epitaxial relationship on Si(111) substrates, that is, the crystallographic orientation of the CaF2 films were aligned in the same direction as that of the Si(111) substrates. These “type-A” CaF2 films were grown by a two step growth method. It was found that surface morphology of GaAs films on the CaF2/Si(111) structures was drastically improved by growth of the “type-A” CaF2 films.
The Growth of Ni Overlayers on Au(100) Buffers Deposited on GaAs(100) and MgO(100) Substrates.
Authors: Gilles B. , Eymery J. , Marty A. , Joud J. C. , Chamberod A.
Published: March 2011

High quality single-crystal Au(100) buffers have been grown on GaAs(100) or MgO(100) substrates via a thin bcc Fe(100) nucleation layer. Using RHEED, LEED and Auger spectroscopy the growth of Ni overlayers at room temperature was observed to follow an epitaxial layer-by-layer mode for 2 monolayers, after which islanding occured. Detailed analysis of the Auger signal reveals that atomic mixing appears within the first completed layer. Grazing incidence diffraction has been used to investigate the structure of 5–10 nm films. A mixture of (100) and (110) grains have been characterized; the latter orientation shows a large number of stacking faults along the [111] direction in agreement with the Au[001] direction.
Epitaxial Growth of B-Doped SiGe Films Using Si-GeH4-B2H6 MBE
Authors: Kunii Yasuo
Published: March 2011

High-crystalline-quality B-doped SiGe films are epitaxial-ly grown on Si(100) substrates using the Si-GeH4-B2H6 MBE system. Both Ge and B profiles in the B-doped SiGe layer are readily controlled using the present system. This technique should be very promising in the bandgap engineering of SiGe base HBTs.
Selective Growth of GaAs on GaAs-Coated Si Substrate by Liquid Phase Electro-Epitaxy
Authors: Sakai Shiro , Ohashi Yasuno
Published: March 2011

The selective LPEE (liquid phase electro-epitaxy) growth of GaAs on GaAs-coated Si substrate prepared by MOCVD has been performed. Several attempts, the use of the insulator melt cap, lowering of the melt height and optimization of the stripe direction, have been tried to increase the lateral growth rate. Very wide (60 μm) lateral overgrowth on the SiO2 mask is obtained by making the stripe window in <010> and equivalent directions and by increasing the lateral current component in the LPEE. The GaAs layer laterally grown on the SiO2 has much less EPD (etch pit density) showing that the defect in the MOCVD-GaAs is blocked by the SiO2. The growth mechanism and the method of increasing the lateral growth rate are discussed.
Solidification Interface Instabilities During Zone Melting Recrystallization Processing of Multilayer thin Film Structures
Authors: Yoon Sharon M. , Hess Christopher K. , Miaoulis Ioannis N.
Published: March 2011

This paper describes a stability analysis of the solidification interface during graphite-strip zone-melting-recrystallization of Silicon-On-Insulator thin film structures. The study focused on instabilities induced by i) variations in the optical properties due to thickness perturbations in the structure and ii) changes in optical properties during phase change. Reflective and emissive interference effects between multilayers play a significant role in the temperature distributions during processing. The presence of a step perturbation imbedded within the film structure affects local heat absorption and resulting temperature profiles. Such disturbances that trigger instabilities at the solid-liquid interface were investigated numerically. Processing speeds which cause interface instability due to optical property variation during phase change were identified.
Numerical Transfer-Matrix Study Of Interfaces In Ising Models
Authors: Novotny M. A. , Richards H. L. , Rikvold P. A.
Published: March 2011

Results are reported for the surface tension, the surface free energy, the surface stiffness coefficient, and the single-step free energy for the Ising model in two and three dimensions. These are obtained by numerical transfer-matrix calculations, testing detailed predictions for the scaling of the largest eigenvalues of the transfer-matrix.
Thin-Film Reactive Interdiffusion in The TI-AL System
Authors: Maugis P. , Blaise G. , Philibert J.
Published: March 2011

We have studied the thermodynamics and kinetics of growth of Al-Ti phases in thin-film interdiffusion couples, A lOOnm thick aluminum layer is vapor-deposited on a poly- or single-crystal titanium substrate, previously etched by ion bombardment. The sample is then annealed during a time ranging from a few minutes to a few hours, at temperatures from 300 to 600°C. The Al atomic fraction vs depth is determined using a sputtering technique, associated with thermo-ionization mass spectrometry (STIMS). At low temperature (300–450°C), titanium diffuses along the grain boundaries of the micro-crystalline aluminum layer, to form an Al-rich phase. At higher temperature (450–500°C), the T1AI3 phase grows rapidly up to the surface. Above 460°C, an intermediate Ti-72at/Al phase grows between TiAl3 and Ti‥ At 600°C, the aluminum layer becomes morphologically unstable.
The Growth Dynamics Of Solid 4He
Authors: Wang Chia-Lai , Agnolet Glenn
Published: March 2011

The interfacial properties of the solid-liquid interface of 4He have been studied at temperatures below 0.5 K using crystallization waves. From the dispersion and damping of the crystallization waves, one can determine the interfacial stiffness, ᾶ, and the interfacial growth resistance, (Km)−1, respectively. Our measured values for ᾶ are consistently smaller than previously published values. At the lowest temperatures, the measured (Km)−1 increases as T4 which is consistent with the prediction that the growth velocity is limited by the scattering of ballistic phonons by the moving interface. We also observe that above 0.25 K the phonon damping is dramatically reduced.
Domain Growth and Wetting in a Low Molecular Weight Binary Fluid System
Authors: Shi Bill Q. , Cumming Andrew W.
Published: March 2011

We present the results of phase-separation experiments performed on the pseudo-binary fluid system guaiacol-glycerol-water. Elastic light scattering and optical microscopy were used to follow the phase-separation after quenches into the coexistence region of the phase diagram. For critical quenches, we observed the well known bicontinuous infinite cluster morphology normally associated with spinodal decomposition, but with two distinct growth modes. In the bulk, at early times we observed L(t) ∼ t1/3 consistent with diffusion driven dynamics, crossing over to L(t) ∼ t1 at later times, as hydrodynamics became important. Near the sample walls, there obtained a novel fast growth with L(t) ∼ t3/2, just as in the case of recent studies with polymer blends, inconsistent with either diffusion or interface driven dynamics. We attribute this large exponent to wetting effects, and the observation of the same phenomenon in such disparate systems as polymer blends and polar organic solvents is strong evidence that the phenomenon is generic to binary systems.
Dislocation Dissociation in the Σ13 Grain Boundary in Silicon
Authors: Sagalowicz Laurent , Beanland Richard , Clark William A. T.
Published: March 2011

Transmission electron microscopy has been used to study the atomic and dislocation structure of deformed and undeformed Σ13 {510} boundary in Si. It is shown that there are several alternative structures for this boundary, which may be separated by imperfect and partial grain boundary dislocations. It is also shown that the dissociation of crystal lattice dislocations which interact with the boundary during deformation results is far more complicated than simple geometrical models applicable in monatomic materials predicts.
High Resolution Analysis of Structure and Chemistry of Grain Boundaries in Silicon
Authors: Kim M. J. , Carpenter R. W.
Published: March 2011

High resolution electron microscopy and high spatial resolution analytical electron microscopy were used to analyze the structure and chemistry of a Σ3 {111} twin boundary in cast polysilicon and a Σ13 (510), [001] tilt boundary in a Si bicrystal. Twin boundaries in cast polysilicon were associated with lattice defects and discrete second phase precipitates. The precipitate was single phase amorphous and faceted on the Si {111} planes. Nanospectroscopy showed mem to be substoichiometric oxide. Similar oxide precipitates, but with different morphology, were also observed on the Σ13 tilt boundary in Si bicrystal, indicating that tilt grain boundaries and steps on twin boundaries were effective heterogeneous sites for nucleation of oxygen containing precipitates. The observed Σ13 tilt boundary exhibited a coincident site lattice periodicity but had an aperiodic interface dislocation core structure. Oxygen that diffused into the boundary in regions where precipitation did not occur may have played a role in modifying the GB core structures, resulting in aperiodicity. For both cases, a detailed analysis of grain boundary atomic structure and precipitate morphology is presented.
Combined Experimentaland Theoretical Determination of the Atomic Structure of the (310) Twin in NB
Authors: Campbells Geoffrey H. , King Wayne E. , Foiles Stephen M. , Gumbsch Peter , Rühle Manfred
Published: March 2011

A (310) twin boundary in Nb has been fabricated by diffusion bonding oriented single crystals and characterized using high resolution electron microscopy. Atomic structures for the boundary have been predicted using different interatomic potentials. Comparison of the theoretical models to the high resolution images has been performed through image simulation. On the basis of this comparison, one of the low energy structures predicted by theory can be ruled out.