bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic Oxygen Plasma Effects on CVD Deposited Diamond-Like Carbon Films
Authors: Hale Jeffrey S. , Synowicki R. A. , Nails S. , Woollam John A.
Published: March 2011

CVD deposited diamond-like carbon (DLC) films have been studied for possible use as a secondary standard for Low Earth Orbit materials degradation. Samples of various thicknesses have been exposed to a simulated Low Earth Orbit atomic oxygen (AO) environment using a plasma asher. Mass loss measurements indicate that DLC degrades at a rate of 0.7 mg/hr which is two to three times the rate of currently used Kapton samples which degrade at a rate of.3 mg/hr. Thickness measurements show that DLC thins at a rate of 77 Angstroms/min. Since DLC is not as susceptible to environmental factors such as moisture absorption, it could potentially provide more accurate measurements of AO fluence on short space flights. Adhesion of DLC films to both fused silica and crystalline silicon substrates has been studied under thermal cycling conditions. Film adhesion to fused silica can be enhanced by sputtering a thin layer of silicon dioxide onto the substrate prior to deposition. In addition to the above, the index of refraction and extinction coefficient of various thicknesses of DLC films has been characterized by Variable Angle Spectroscopic Ellipsometry.
Si-N Bonding at The SiO2/Si Interfaces During Deposition of SiO2 by the Remote Pecvd Process
Authors: Ma Y. , Yasuda T. , Habermehl S. , Lucovsky G.
Published: March 2011

Thin films of SiO2 were deposited on Si substrates by remote PECVD following an in-situ cleaning/surface passivation with atomic-H. Si-N bonds were found in the immediate vicinity of the SiO2/Si interface when nitrous oxide, N2O, was used as O-atom source gas in the remote PECVD process. Si-N bonds, as well as Si-surface roughening produced by H-atom etching, contribute to the formation of high densities of midgap trapping states, Dit ∼1011 cm−2 eV−1, at the SiO2/Si interface. Eliminating the H-atom processing step, and exposing the Si surface to plasma-generated O-atoms prior to the SiO2 deposition: i) eliminated Si-N bonding at the Si/SiO2 interface; ii) reduced midgap Dit to ∼ 1–3×1010 cm−2eV−1 iii) eliminated surface roughening; and iv) improved process latitude and reproducibility.
Dynamics of Graphite Photoablation
Authors: Murray P. T. , Peeler D. T. , Dempsey D. V.
Published: March 2011

Speed distributions were determined for the ions, ground state and electronically-excited neutrals ejected from a graphite target by 248 nm laser ablation. Mass distributions were measured for the laser-ejected ions. The measurements were carried out normal to the graphite target as well as at an angle of 45°. Significant differences were observed in both the speed and mass distributions at the two angles.
Effects of Fluorine Implantation into Hydrogenated Amorphous Silicon
Authors: Wong S. P. , Peng Shaoqi , Ke Ning , Liu Jingxi
Published: March 2011

Multiple-energy implantation of fluorine into rf glow discharge deposited hydrogenated amorphous silicon (a-Si:H) thin films has been performed. It is found that the optical gap decreases with the implanted fluorine concentration CF from 1.56 eV for the unimplanted sample to 1.40 eV for the sample with CF of 3×1021 cm−3. Results of the Staebler-Wronski experiment show that the ratio between the electrical conductivity before and after illumination, as well as the ratio between the photo- and dark conductivity, decrease also with Cp. Electrical measurements show that there is significant decrease in the conductivity activation energy Ea with CF for samples annealed at or below the substrate temperature TS during deposition. But for samples annealed at temperatures higher than TS, Ea was found to change back to values close to that of the unimplanted sample. A large shift to higher energy for one peak in the photoluminescence spectra at 77K has been observed, from 1.34 eV of the unimplanted sample to around 1.6 eV for the implanted samples, though with almost one order of magnitude weakening in intensity. It is also observed that ESR splitting has been induced in the fluorine implanted samples. The g-factors of the two resonances are determined to be 2.003 and 2.006, respectively. For the g=2.006 resonance, the spin density increases markedly after implantation but is essentially independent on CF before annealing and effectively reduced or eliminated after annealing. For the g=2.003 resonance, the spin density increases rapidly with CFp especially in the range from CF = 1×1020 to 1×1021 cm−3 before annealing and reduces only slightly after annealing.
The Role of Hydrogen in Laser Deposition of Diamond-Like Carbon
Authors: Thebert-Peeler D. , Murray P. T. , Petry L. , Haas T. W.
Published: March 2011

Thin films have been grown on Si (100) substrates by pulsed laser evaporation of graphite using both IR and UV radiation. The character of the resulting film is found to be independent of the presence of H°. Diamond-like films are found to be a result of low (RT) temperature deposition of the higher energy incident particles of the UV (versus IR) laser ablation process.
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.
Laser Cvd of Tungsten on Silicon Oxynitride
Authors: Izquierdo R. , Lecours A. , Meunier M.
Published: March 2011

Laser direct writing of tungsten from WF6 onto 0.6 μm thick films of silicon oxynitride on silicon using an argon-ion laser beam is investigated. XPS studies show that WF6 is chemisorbed on the oxynitride surface and that nitrogen plays a role in this adsorption. Deposits have good adhesion, columnar growth structure and resistivities ranging from 13 to 25 μΩ-cm. The deposition conditions significantly affect the deposit morphology and profile. In particular, increasing the hydrogen pressure increases the linewidth but reduces the thickness. Mass transport phenomena are invoked to explain these effects.
Thermal and Photoinduced Decomposition Pathways of Arsine on GaAs(100)
Authors: Zhu X.-Y. , Wolf M. , Huett T. , White J. M.
Published: March 2011

We have studied the thermal and photoinduced dissociation pathway of AsH3 on the Ga-rich GaAs(100) surface. Arsine adsorbs molecularly at 115 K and dissociates upon either heating to above 140 K or upon irradiation with 3.5 - 6.4 eV photons. The decomposition of arsine is accompanied by the formation of surface Ga-H species, which are thermally and photochemically more stable than surface AsHx. A comparison of the wavelength dependence for adsorbed and gas phase arsine reveals that the excitation mechanism of the AsH3 surface photochemistry is substrate mediated, which probably involves a charge transfer between surface states and the adsorbate.
Laser-Induced Deposition of Buried Insulator Lines in Mn-Zn Ferrite
Authors: Lu Y.F. , Takai M.
Published: March 2011

Maskless etching of single crystalline Mn-Zn ferrite (MnO: ZnO: Fe2O3 = 31:17:52) has been investigated in a SiCl4 atmosphere by Ar+ laser irradiation. The ferrite substrate can be thermochemically etched by a single scan of a laser beam. Silicon oxide was deposited simultaneously in the etched groove. The deposited silicon oxide lines were investigated by AES, XPS and RBS. It is found that the deposited lines were stoichiometric SiO2 under specific conditions. The etching and deposition process can be controlled by changing the SiCl4 gas pressure. A planarized SiO2 layer buried in ferrite was found not to affect the magnetic characteristics of the ferrite layer.
GaAs and Si Assisted Etching using a Scanning Tunneling Microscope
Authors: Baba Masakazu , Matsui Shinji
Published: March 2011

GaAs etching with Cl2 gas is studied with a scanning tunneling microscope (STM). Both Cl2 gas and tunnel electron assist etching occur under the tip during scanning and the etching profile is found to depend on the gas flow time. GaAs and Si patterns with nanometer dimensions are fabricated by STM assist etching with a very low voltage (-IV). Also atomic layer etching of GaAs is demonstrated by STM assist-etching using a Cl adlayer.
Activation of the Si(100)/Cl2 Etching Reaction at High Cl2 Translational Energies
Authors: Campos Francis X. , Weaver Gabriela C. , Waltman Curtis J. , Leone Stephen R.
Published: March 2011

Exposing a Si(100) surface to a pulsed beam of neutral Cl2 with high translational energy results in etching at a rate faster than that seen with chlorine at thermal energies. The Cl2 beam used in these experiments is produced by laser vaporization of cryogenic films. It has a broad energy distribution which can be varied by changing laser energy and film thickness. Beams with mean energies as low as 0.4 eV result in etching =10 times faster than etching by thermal Cl2. When Cl2 beams are used which have considerable flux above 3 eV, the etching rate increases by a further factor of 3.6 ± 0.6. This rate increase, which occurs at energies just above the Si-Si bond energy, suggests that kinetic energy can be efficiently utilized to break surface bonds.
Ge Surface Displacements Due to Low Energy Particles
Authors: Picraux S. T. , Horn K. M. , Chason E. , Tsao J. Y. , Bedrossian P. , Klitsner T. , Brice D. K.
Published: March 2011

The production of surface defects by low energy 4He and Xe ions incident on very smooth Ge(001)2x1 surfaces is reported. Roughening at -50°C by 100-500 eV ions is measured by RHEED in real-time using the intensity of the out-of-phase specular beam. For He, the surface displacements per ion range from 0.05 to 0.3 and are comparable to our binary collision calculated surface vacancy production rate for a displacement threshold energy of 11 eV (3/4 of bulk value). For Xe, the displacement rate ranges from 2 to 10 (∼30x higher) and falls between the calculated total vacancy and total defect (vacancy + interstitial) production rates.
Microstructures of Si(111) on Ion Sputtering and Electron Annealing
Authors: Al R. , Savage T. S. , Xu P. , Zhang J. P. , Marks L. D.
Published: March 2011

The microstructure evolution during preparation of thin Si(111) samples for surface sensitive imaging has been studied using ultra-high vacuum (UHV) transmission electron microscopy (TEM). The effects of ion beam sputtering and electron annealing have been investigated. A unique and routine sample preparation method for surface sensitive TEM imaging that combines TEM sample preparations with surface science sample preparation was developed. The microstructure evolution during the sample preparation process was studied in detail.
X-Ray Fluorescence Determination of Low Metal Concentration in Surface Masking Layers on Organic Polymers
Authors: Hutton Richard S. , Taylor Gary N.
Published: March 2011

A highly sensitive x-ray fluorescence (XRF) technique has been developed for the determination of low metal concentrations in the etch resistant layer of surface-imaged photoresists. The samples may be analyzed quickly and the method is applicable to a wide variety of surfaceimaging processes. For each metal of interest the XRF spectrometer is easily calibrated using polymer films containing known concentrations of a metal-containing reagent. Examples of the application of this technique to the analysis of Ti, Si and Zr-containing films are described.
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 asgrown 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.
Low Energy Ion Beam Modification of High Performance Polymer
Authors: Jeong Hyo-Soo , White R. C.
Published: March 2011

Ion beam modification of polyimide (PI) by low energy and surface analysis were performed using XPS. The surface chemistry was monitored as a function of ion dose. The results indicate that even low energy ion beam (LEIB) induces a drastic change in chemical compositions on the PI surface, and the modification begins to occur at the onset of beam treatment, contrary to previous observations. Damage level is severely restricted to surface region. It is also proven that LEIB modification is a direct way to control interface chemistry.
Laser Etching of Ceramics for Defining Slider Air-Bearing Surfaces for Magnetic Recording Heads
Authors: Khan Jamal
Published: March 2011

A laser etching process was used to etch air-bearing surface patterns (cavities) on sliders for magnetic recording heads. Results on projection through mask as well as maskless etching of patterns on the TiC-A12O3 ceramic substrate and encapsulant alumina film on the surface are described. Pattern dimensions and location, along with laser operating parameters, are defined via a computer software program in the maskless etching process, and no external hard masks were used. A combination of maskless etching processes, using a Q-switched Nd:YAG laser for most of the ceramic substrate material in the back of the cavity and an excimer laser system for the alumina coating and nearby areas in the front, was found to give the best results.
Large Area Photochemical Dry Etching of Polymers with Incoherent Excimer UV Radiation
Authors: Esrom Hilmar , Zhang Jun-Ying , Kogelschatz Ulrich
Published: March 2011

Photochemical dry etching and surface modification of different polymers, e.g., poly-methylmethacrylate (PMMA), polyimid (PI) and poly-ethylene terephthalate (PET) was achieved with an incoherent excimer UV source. Decomposition and etch rates of PMMA were determined as a function of UV intensity and exposure time at different wavelengths λ = 172 nm (Xe2*), λ = 222 nm (KrCI*) and λ = 308 nm (XeCI*). The morphology of the exposed area of PMMA was investigated with SEM. The etching of the polymers can be explained as a result of extensive photooxidation. The results are compared with data obtained from mercury lamp and excimer laser experiments.
Oxide Phase Formation in Excimer Laser Processed Ti Alloy
Authors: Jervis T. R. , Hubbard K. M. , Zocco T. G.
Published: March 2011

Excimer laser surface processing of Ti-6A1-4V results in substantial surface oxygen incorporation as measured by the narrow resonance in the elastic scattering of a particles at 3.05 MeV. Single pulse processing at 1.0 J-cm−2 results in transformation from the original a + β grain structure to a martensite structure. Multiple pulse processing results in oxygen incorporation proportional to the number of pulses during processing, but this is primarily reflected in the depth of the oxygen containing layer. A maximum oxygen to titanium ratio of 1.0 was observed in the surface layer. This was confirmed by transmission electron microscopy (TEM) which showed the development of a fine-grained equiaxed TiO surface layer from a phase mixture of Ti alloy with TiO precipitates. Concentration vs. depth profiles show that this layer is approximately 400 nm thick after 40 pulses. Further processing with a total of 60 pulses results in coarsening of the grains and an increase in the thickness of the layer. The TiO precipitate concentration increases gradually, becoming apparent in electron diffraction patterns after 30 pulses. No other oxide phases are observed, the TiO developing directly from the metallic phases. In particular, we do not observe the formation of Ti2O prior to the formation of the TiO, or the formation of TiO2.
In-Situ Ellipsometry Study of Pulsed Laser Deposited ZnO Films
Authors: Pittal Shakil , Mcconville L.A. , Tanno 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.
Generation of Shock Waves in Confined Excimer Laser Ablation of Polyimide
Authors: Zweig Adrian D. , Deutsch T.F.
Published: March 2011

We study acoustic effects associated with the ablation of polyimide under water confinement. Ablation launches a shock in the target. After the shock propagates into the surrounding water we measure its velocity with an optical probe system. In the water the shocks decay after propagating a few hundred microns. The peak shock pressure scales with the square root of the laser fluence. Our observations can be explained by a simple model that interprets the generated pressures as being due to the heating of a confined ideal gas.
Photophysics of Polyatomic Species Ejection Following Uv Laser Ablation of Single Crystal Bi2Sr2Ca1Cu2O8
Authors: Wiedeman Lawrence , Kim Hyun-Sook , Helvajian Henry
Published: March 2011

A series of experiments have been conducted which probe the origin of the polyatomic ions (e.g., Sr2O+, BiCu+) measured following the low fluence, pulsed UV laser irradiation of crystalline Bi2Sr2CaCu2O8 (BiSrCaCuO). The photoejection of polyatomic species presents a problem for the pulsed laser deposition (PLD) technique. The deposition of polyatomic products could limit epitaxial growth during thin film material processing. Our results indicate that the polyatomic species are not the consequence of a gas phase recombination, but are in fact directly produced. All experiments are done at laser fluences below that required for above surface plasma formation. As such, our results do not address the formation of large clusters within the dense plume in high fluence laser ablation.
Photon-Single Phonon Coupling at Polar Crystal Surfaces: Infrared Optical Anisotropy Spectra
Authors: Mochan W. Luis , Recamier Jose , Monsivais Guillermo , Barriga Lucia Diaz
Published: March 2011

We extend a formalism for the calculation of the surface-induced infrared anisotropy spectra of cubic polar crystals, in order to incorporate surface relaxation, reconstruction, and in general, surface modifications to the dynamic matrix. We calculate the reflectance anisotropy of a model (110) GaAs surface. The spectra have a rich structure which can be related to critical points of the phonon dispersion relation, and to coupling to surface states and surface resonances. The results display a very large sensitivity to the surface parameters, indicating that the surface induced anisotropy can be employed as an optical surface probe in the far IR.
Electron, Ion and Photon Beam Processing
Authors: Gamo Kenji
Published: March 2011

Beam processing techniques are increasingly important because of their unique capability as nano-device fabrication techniques. These are low temperature processing, high spacial resolution, high material and spacial selectivity and anisotropy, etc. For device fabrication, reduction of processinduced damage is crucial. In the present paper, basic characteristics of electron, ion and photon beam processing for etching and deposition are compared with putting emphasize on the effect of damage and promising techniques to minimize damage.
Slim: a Personal Computer Based Software for Simulation of Laser Interaction with Materials
Authors: Singh Rajiv K. , Viatella John
Published: March 2011

A user-friendly, personal computer (PC) based routine called SLIM [Simulation of Laser Interaction with Materials] has been developed to understand the non-equilibrium effects of high intensity, short laser pulses on different materials. By employing an accurate implicit finite difference scheme with varying spatial and temporal node dimensions, the time-dependent thermal history of laser-irradiated material can be accurately and quickly determined. This program can take into account the temperature dependent optical and thermal properties of the solid, time dependent laser pulse intensity, and formation and propagation of the melt and/or vaporization interfaces induced by intense laser irradiation. The program can also simulate thermal effects on multilayer structures exposed to pulsed laser irradiation It is expected that this simulation routine will be indispensable to all researchers working in the area of pulsed laser processing of materials, including rapid heating, melting, annealing, laser doping, laser deposition of thin films and laser solidification processing.
Resistless Etching of SiO2 by Two Color Excimer Lasers
Authors: Obara T. , Murahara M.
Published: March 2011

Resistless etching of thermal oxide silicon filmes were demonstrated by ArF & KrF excimer lasers, and CC12F2 gases. CC12F2 was decomposed by ArF excimer laser light, and CF2 radicals were produced. These radicals, which have absorption band nearby 250nm, were vary stable. Then the circuit pattarned KrF laser light was irradiated on the SiO2 in an atomsphere of CF2 radicals. As thse result, the etching pattern of 2 μ m width was performed.
Morphological Features of the Solid-Liquid Interface of a Gallium Film
Authors: Robinson Richard D. , Miaoulis Ioannis N.
Published: March 2011

This paper presents a new experimental method to investigate solid-liquid interface morphologies during Zone-Melting-Recrystallization at lower than the typical processing temperatures. Gallium films were used as a substitute for silicon films. In situ preliminary investigation identified three phenomena typically occurring during ZMR of silicon films: a) Transition from planar to dendritic to cellular morphologies was observed for different processing conditions; b) cell period proved to be dependant on scanning velocity; c) instabilities at the solidification interface at low heating strip temperatures were caused by supercooling and optical property variations as the material changed phase.
Morphological Changes in Rod-Shaped Precipitates With Internal Boundaries: Finite Difference Analysis
Authors: Choy Jun-Ho , Hackney S. A. , Lee J. K.
Published: March 2011

Shape evolution of rod-shaped precipitates due to surface diffusion has been studied under the conditions of constant volume and isotropie interfacial free energy. The shape evolution depends strongly on both the initial aspect ratio and the grain boundary groove angle. For a finite rod with one grain boundary, the morphology evolves into an equilibrium shape made of spherical portions if its aspect ratio and the groove angle are small. Increase in the aspect ratio causes a boundary splitting. For an infinite rod with periodic boundaries, three types of morphological evolutions are observed. When the relationship between the aspect ratio and the groove angle satisfies a certain critical condition, the shape evolves into an equilibrium. If the relationship deviates significantly from this condition, an ovulation process takes place at each location of the internal grain boundaries. When the deviation is intermediate, the morphology undergoes an oscillation in a quasi-dynamic state between the process toward an equilibrium shape and the ovulation process. The ovulation process due to internal grain boundaries is found to precede the Rayleigh spheroidization process.
Kinetics of Explosive Crystallization Phenomena in Amorphous Silicon and Crystal Structure of the Layers Formed
Authors: Glaser E. , Bartsch H. , Andrä G.
Published: March 2011

Systematic relations are shown between the parameters controlling explosive crystallization in silicon (temperature, width of a liquid zone, and gradient of melt undercooling), the kinetics of the crystallization process, the predominance of preferential growth directions, and the crystal structure observed. Three typical regions of crystallization are found: (a) cellular growth of a laminated crystalline layer controlled by the formation of high densities of twins at a nearly plane liquid/solid interface, (b) cellular-dendritic growth of crystal lamellae characterized by branching of a curved interface, and (c) formation of a diffuse “slush zone” due to random nucleation in a-Si and grain growth in the liquid zone.
Spinodal Decomposition of the Interface in a Nonlinear Growth Model with Noise
Authors: GoluBovic Leonardo , Karunasiri R. P. U.
Published: March 2011

We consider a non-linear version of Edwards-Wilkinson interface model for the growth in the presence of a collimated partjcie flux. We include both surface tension and surface diffusion relaxation. In a range of positive small values of the surface tension, the interface develops a state which fulfills standard criteria for spinodal decomposition. This suggests the existence of a phase transition from the ordinary state with the interface perpendicular to the incoming flux to a novel, noue.induced state with the interface apontaneously tilted with respect to the direction of the flux.
Impurity Segregation in A/A1−xBx Heterostructures During Liquid Phase Epitaxy
Authors: Cook Stephen J. , Clancy Paillette
Published: March 2011

The segregation behavior of model dopants during liquid phase epitaxy of A/A1−xBx heterostructures is studied using Non-equilibrium Molecular Dynamics computer simulation. Interatomic interactions are modelled using the Lennard-Jones potential and the dopant “B” atoms are assigned to have a different diameter than the host “A” atoms. The extent of segregation as a function of regrowth velocity is found to be well represented by the Continuous Growth Model of Aziz for solidification on the (111) orientation. The mechanism of segregation, however, more closely resembles the physical picture due to Jackson, Gilmer and Leamy.
Surface Microstructural Evolution of Ultrathin films by Real time Spectroscopic Elupsometry
Authors: Collins R. W. , An Ilsinan , Li Y. M. , Wroński C. R.
Published: March 2011

Vapor deposition of smooth, microstructurally uniform amorphous films on dissimilar substrates requires coalescence of clusters that form during initial nucleation. We have developed techniques that provide sub-monolayer sensitivity to this phenomenon, relying on real time spectroscopie ellipsometry observations during ultrathin film growth (thicknesses < 50 Å). An investigation of tetrahedrally-bonded amorphous semiconductors lends insights into the role of nucleation density and adatom surface diffusion in determining the ultimate atomic-scale roughness on the film.
Simulation of Crystal Growth With Facetted Interfaces
Authors: Roosen Andrew , Taylor Jean E.
Published: March 2011

We present a method for simulation of crystal growth using completely facetted interfaces and the definition of curvature appropriate to such interfaces. The representation of these surfaces, as facets with fixed normal directions, variable distances, and semi-fixed adjacencies, is quite different from that in other methods. It is flexible as to possible growth rules, it appears to avoid the problems involved in measuring curvature and in detecting and making topological changes, and it runs relatively fast. We expect it to be a valid method to approximate growth with any isotropie or anisotropie surface energy and kinetics. The use of the method is demonstrated in dendritic crystal growth and in Ostwald ripening.
Influence of Compression Process on Optical Properties of PDA Langmuir-Blodgett Films
Authors: Yuan Chun-wei , Lu Chun-lin , Liang Yong , Gu Ning , Wei Yu
Published: March 2011

In performing compression-expansion-recompression process during preparation of diacetylene (DA) monolayer, the change in colour of polydiacetylene (PDA) LB films was observed and more ordered structure of the films was achieved. The effect on optical properties could be ascribed to better arrangement of DA monomer which favoured the formation of PDA films in blue-form in polymerization.
Simulations of Microscopic Wetting Phenomena on Self-Assembled Monolayers.
Authors: Hautman Joseph , Klein Michael L.
Published: March 2011

Recently developed methods of fabricating layers of long-chain molecules with functional tailgroups have provided new possibilities in the design and modification of surface properties.fi] An ui.derstanding of the relationship between the detailed molecu.'.ar structure and macroscopic properties, such as wetting and adhesion, is needed to facilitate the design of surface characteristics for specific applications such as coatings, adhesives, optical devices and substrates for binding biomolecules. [1, 2]
Electrochemical Roughening and Annealing of Au(111) Surfaces in Perchloric and Sulfuric Acid Electrolytes Studied by STM
Authors: Hanson Karrie J. , Green Michael P.
Published: March 2011

A technique commonly used as the final stage of cleaning gold electrode surfaces is to electrochemically form and reduce a monolayer of oxide on the surface. We have investigated the changes on the Au(111) surface during this procedure using in situ electrochemical scanning tunneling microscopy.
Electrical and Photoelectrochemical Characterization of CDS Particulate Films by Scanning Electrochemical Microscopy, Scanning Tunneling Microscopy, and Scanning Tunneling Spectroscopy
Authors: Zhao Xiao Kang , McCormick Larry , Fendler Janos H.
Published: March 2011

Cadmium sulfide particulate films have been generated at monolayer interfaces. Controlled and slow infusion of hydrogen sulfide onto compressed monolayers prepared from cadmium arachidate resulted in the formation of covalent metal sulfide bonds at a large number of sites at the monolayer-aqueous interface. The initial nucleation resulted in the downward growth of well-separated, metal-sulfide microclusters which grew in height and width and coalesced into interconnected arrays of semiconductor particles.
X-ray Scattering from Interfaces
Authors: Vlieg E. , Van Der Vegt H. A.
Published: March 2011

X-ray diffraction has found an increasing use in the characterization of surface structures. Due to the high penetration depth of X-rays, the technique is also very suitable for the study of buried interfaces. We will give a general outline of the technique, and then discuss two examples concerning epitaxial growth.
In-Situ X-Ray Reflectivity Study on Growth Dynamics of Sputter Deposited Gold on Silicon
Authors: Chiarello R. P. , Kim H. K. , Roberts T. , Miller D. J. , Kampwirth R. T. , Gray K. E. , You H.
Published: March 2011

We performed in-situ x-ray reflectivity measurements to study the growth dynamics of gold sputter deposited onto silicon using an x-ray scattering chamber equipped with a faced magnetron source where the substrate is held at a right angle relative to the sputtering guns. By operating the guns at low power (1 watt) and under 20 mTorr Ar, we could control the gold deposition rate to less than 1Å/sec. The observed x-ray reflectivity for gold deposited onto a silicon substrate at 300 K and 400 K is consistent with nucleated island growth for average gold particle sizes less than 50 Å. Above 50 Å, the reflectivity data indicates that the gold film uniformly covers the silicon surface, and that as the film thickness is increased the gold-vacuum interface gets progressively rougher. Detailed analysis of room temperature data is in progress, as is the temperature dependence on the roughness of the gold vacuum interface.
The Finite Size Effect on The Metal-Insulator Transition of VO2 Films Grown by MOCVD
Authors: Kim Hyung Kook , Chiarello R. P. , You Hoydoo , Chang M. H. L. , Zhang T. J. , LAM D. J.
Published: March 2011

We studied the finite size effect on the metal-insulator phase transition and the accompanying tetragonal to monoclinic structural phase transition of VO2 films grown by MOCVD. X-ray diffraction measurements and electrical conductivity measurements were done as a function of temperature for VO2 films with out-of plane particle size ranging from 60–310Å. Each VO2 film was grown on a thin TiO2 buffer layer, which in turn was grown by MOCVD on a polished sapphire (1120) substrate. The transition was found to be first order. As the out-of plane particle size becomes larger, the transition temperature shifts and the transition width narrows. For the 60Å film the transition was observed at ∼61°C with a transition width of ∼10°C, while for the 310Å film the transition temperature was ∼59°C and the transition width ∼2°C. We also observed thermal hysteresis for each film, which became smaller with increasing particle size.
High-Resolution Leed Study of Intermixing of Fe Films on Au(001) Surface
Authors: He Y.-L. , Wang G.-C.
Published: March 2011

Ultrathin ferromagnetic Fe films have been grown on an Au(OOl) surface. Using the angular profile measurements of High-Resolution LEED (HRLEED), we show the inho-mogeneities at the interface due to atomic place exchange between Fe and Au atoms can drastically change the angular intensity distributions of diffraction beams. The contributions from the inhomogeneities on the surface can be properly decoupled from the total angular intensity distributions. Through the energy dependent angular profile analysis of diffraction beams, we have quantitatively determined the degree of inhomogeneous atomic intermixing at elevated annealing temperatures.
Electron Microscope Studies of Some Vapor Deposited Materials: Nucleation, Epitaxial Growth and Surface Topography
Authors: Krakow William
Published: March 2011

The nucleation and epitaxial growth of deposits at both low and high temperature substrate conditions and the resulting two and three dimensional growth modes have been investigated using electron diffraction and transmission electron microscopy. At high temperatures, the growth of small particles such as Au, Pt and Ge grown under low rate conditions similar to MBE are revealed by lattice imaging. Using an intermediate bufler layer Ag film, surface growth of (100) and (310) Au thin film layers are revealed by diffraction contrast to be in a step ledge growth regime. While the above investigations were performed ex situ to the microscope vacuum environment, an in situ evaporator has been also been installed on a high resolution electron microscope. Observations can be made in real time of cluster growth from atomic diameters on up. The resulting atomic motion around cluster edges is similar in appearance to surface melting.
Electronic Structure of Defects on Reduced TiO2 (Rutile) Surfaces
Authors: Zhong Qian , Vohs John M. , Bonnell Dawn A.
Published: March 2011

Several TiO2 (110) surfaces, reduced via different mechanisms, were investigated in ultra-high vacuum using Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) to determine the effect of reduction on the surface atomic and electronic structure. Defect chemistry and its relation to the change of property and structure are discussed.
Growth of Crystalline Superlattices of Aluminum Nitride/Zirconium Nitride on SI(111): Roughness and Layer Interruptions
Authors: Meng W. J. , Heremans J.
Published: March 2011

We report on growth of crystalline superlattices of aluminum nitride/zirconium nitride on aluminum nitride buffered Si(111) substrates. We observed increased buffer layer surface roughness as compared with the buffer/Substrate interface. This roughness in turn influences the quality of the superlattice. We report results of surface morphology examination as a function of growth rate and substrate temperature.
Epitaxial Growth of Bi2Sr2CuO6 Thin Films on Single Crystal Surfaces.
Authors: Matsumoto Takuya , Kawai Tomoji , Kawai Shichio
Published: March 2011

Epitaxial growth of Bi2Sr2CuO6 thin films on a SrTiO3, a misoriented SrTiO3 and a Bi2Sr2CaCu2O8 single crystal have been performed using computer-controlled laser molecular beam epitaxy. On the SrTiO3 substrate, the 2201 films consist of two types of domains whose b-axes are perpendicular to each other. In contrast, the 2201 film on the 2212 single crystal has a complete single type of domains. Layer-by-layer growth with a half unit cell thickness of 2201 films is observed.
Crystallization of Amorphous Silicon-Aluminum thin Films: IN-SITU Observation and Thermal Analysis.
Authors: Konno Toyohiko J. , Sinclair Robert
Published: March 2011

The crystallization of sputter-deposited Si/Al amorphous alloys was examined by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). In-situ high-resolution TEM reveals the existence of an Al layer between the amorphous matrix and the growing crystalline phase. The activation energy for the growth is about 1.2eV, roughly corresponding to the activation energy of Si diffusion in Al. These two observations support the view that a crystallization mechanism, in which an Al buffer layer provides the shortest reaction path, is responsible for the reaction. The product microstructure exhibits secondary crystallization at a higher temperature.
The Importance of Thickness to the Crystallization of Amorphous thin Films
Authors: Cardinale Gregory F. , Farrens S. N. , Howitt D. G.
Published: March 2011

The crystallization of an amorphous thin film, when it is annealed, can be described in terms of the latent heat of the transformation and an activation energy which depends upon the configurational entropy of the surface of the crystallizing interface. An expression is derived for anatase, the low temperature form of titanium oxide, which is consistent with the growth that is observed.
Simulation and Modeling of Kinetics of Silicon Oxidation in the thin Oxide Regime
Authors: Dutta Tirthankar , Ravindra N. M.
Published: March 2011

Thermal oxidation of Silicon in the thin regime is of vital importance to VLSI device engineers because thin layers of SiO2 are exclusively used as the gate dielectric for high performance of MOS devices. There exists a number of models to explain this kinetics of oxidation. However there is a considerable variance among the reported rate constants, which are supposed to describe the oxidation process. Rather than arriving at an alternative model, the present study aims at simulation of existing models of oxidation in dry oxygen, with a recent set of experimental data and arrive at the best possible model and provide accurate rate constants for oxidation in dry oxygen. These experimental data have been obtained, earlier, using high-resolution transmission electron microscopy (HRTEM) and ellip-sometry techniques to measure thicknesses of silicon oxide, grown at 800° in dry oxygen, in the thickness range of 2–20 nm.
In-Situ TEM Observation of a Structural Change in a Near Σ=3-Twist Boundary In Ordered Cu3Au.
Authors: Tichelaar F. D. , Schapink F. W.
Published: March 2011

In this paper the structure of a (011)-Σ=3 twist boundary in ordered Cu3Au is analysed geometrically. Wrong nearest-neighbour bonds can be avoided by facetting on an atomic scale along common {112} planes, together with a rigid-body translation parallel to one of the facets as measured in earlier work. In the specimen different translational states were found in different areas of the [165]-Σ=3 boundary by transmission electron microscopy (TEM). One of the translations was in agreement with the model, the other was associated with a presumably energetically more unfavourable structure. The in situ observation at 230 °C of the motion of the dislocation separating the different boundary areas was associated with a transformation of the boundary structure with the higher energy into the more favourable structure. Therefore, it is likely that the driving force of the dislocation motion was a difference in boundary energy.
Shape Transformations of Ge Precipitates in Al
Authors: Lours P. , Westmacott K. H. , Dahmen U.
Published: March 2011

Ge precipitates in Al-Ge alloys have been observed to undergo a transformation in shape during in-situ temperature cycling in a high voltage electron microscope. Octahedral precipitates with a parallel-cube orientation relationship spheroidized on heating and refaceted to the octahedral shape on cooling. This shape transformation was essentially conservative if the temperature excursions were kept small. These observations are discussed in terms of an interface roughening transformation.
The Role of Surface Stress in the Faceting of Stepped Si(111) Surfaces
Authors: Williams Ellen D. , Phaneuf R. J. , Bartelt N. C. , Świe¸ch W. , Bauer E.
Published: March 2011

The nucleation and growth of facets on stepped Si(111) have been observed in real time using the newly developed technique of low-energy electron microscopy (LEEM). The results show that the growth of an isolated facet spontaneously stops at a well-defined size. This is a surprise as classical theories of the growth of linear facets predict a continuous growth, which would only be limited by collisions with neighboring facets. We review predictions that elastic interactions between surface regions of different structure can stabilize finite size domains and facets. We show that a model in which elastic relaxations caused by the facet boundaries stabilize a finite facet width is entirely consistent with the experimental observations.
The Effect of Initial Growth Conditions on the Tilting of Lattice Planes in InP-ON-GaAs Heterostructures
Authors: Riesz Ferenc , Lischka K. , Rakennus K. , Hakkarainen T. , Pesek A. , Koppensteiner E.
Published: March 2011

The relative misorientation (tilt) between the epilayer and substrate (400) lattice planes of InP epilayers grown by gas-source molecular beam epitaxy on (100) GaAs substrates misoriented towards the (110) plane was studied by high resolution x-ray diffraction. For the growth temperature of 490–500°C, the direction of the relative tilt was nearly coincident with the direction of the substrate lattice plane tilting. In contrary, when a buffer layer was deposited at a lower temperature of 400–450°C prior to growth, an azimuthal rotation of about 45° was found between the directions of the relative tilt and the substrate lattice plane tilting. In order to explain the results, a temperature-dependent anisotropic nucleation model is proposed.
The Interaction of Bulk Defects with Surface Reconstructions
Authors: Dunn D. N. , Marks L. D. , Merkle K. L.
Published: March 2011

It is demonstrated by ultra-high vacuum transmission electron microscopy that subsurface dislocations and stacking faults strongly interact with the Au (001) (5×n) surface reconstruction. This effect is found in both bulk single crystal and thin fílm samples.
Analysis of Faceted Growth Hillocks in MOCVD Grown Epitaxial HgCdTe on GaAs with a Nuclear Microprobe
Authors: Jamieson David N. , Dooley S. P. , Russo S. P. , Johnston P. N. , Pain G. N. , Leech P. W.
Published: March 2011

Hg1-xCdxTe epitaxial layers on GaAs substrates grown by Metal Organic Chemical Vapour Deposition (MOCVD) display growth defects resembling pyramidal faceted hillocks which appear to originate from defects originally present on the substrate. For <100> oriented GaAs substrates and normal growth conditions, these growth defects have an areal density of 1–1000 mm-2. The size of the hillocks depends on the layer thickness and they have the potential to degrade performance of optoelectronic devices fabricated in the epitaxial layers. Nuclear microprobe analysis, performed with a 2 MeV He+ beam focused to less than 5 μm in diameter, has allowed the hillocks to be imaged with the technique of Channeling Contrast Microscopy (CCM). Channeling spectra, obtained by Rutherford Backseat tering Spectrometry (RBS) of the hillocks themselves, showed that the χmin was 13 %. This was similar to the χmin of the high quality single crystal surrounding material. The CCM images also revealed extensive regions of poor channeling, with shapes that suggested that the regions originally arose from scratches in the substrate. These poor channeling regions were not readily observable by other techniques.
In-Situ Transmission Electron Microscopy of the Etching of Silicon (111) Surfaces by Oxygen
Authors: Gibson J. M. , Ross F. M.
Published: March 2011

Silicon (111) surfaces have been etched in-situ in a ultra-high vacuum transmission electron microscope. Surface steps are observed to flow during etching, so that Si atoms are removed only from steps. This is in contrast to the behavior during the formation of an oxide layer reported previously. The nucleation of steps and their interaction with surface impurities is described.
Dissolution and Growth Kinetics of Small Crystals in Liquids
Authors: Uttormark Michael J. , Thompson Michael O. , Clancy Paulette
Published: March 2011

Molecular Dynamics simulations of the melting of small crystalline clusters (≃800 atoms) in the liquid have been performed at various temperatures above the equilibrium melting point. The melting rates as functions of size and temperature are derived and compared to that predicted by Classical Nucleation Theory. It is found that the driving force for the melting of clusters does not follow the form assumed in the theory, and that this difference is most apparent for clusters containing less than 300 atoms. The implications of these findings on nucleation phenomenon and possible sources for the discrepancies are discussed.
Diffusion Limited Interface Kinetics in Multicomponent Systems
Authors: Hopfe William D. , Morral J. E.
Published: March 2011

The stability of phases in materials can be related to reactions occurring at their interfaces, for example fiber/matrix reactions in composites. The reaction can be modelled in a simple way, even for multicomponent systems, when it is diffusion controlled and when no intermediate phases form. In the current work a model is proposed that assumes local equilibrium at the interface and small concentration differences in each phase. The physical properties required for the model are the “square root diffusivity” for each phase and the applicable phase diagram. The model is applied to predicting concentration profiles and interface velocities for the reaction of a B2 aluminide containing Ni-34at%Cr-12at%Al with various Ni-rich, gamma solid solutions containing Cr and Al. The example shows how varying the gamma composition can alter the aluminide stability with respect to dissolution or growth. In addition, a simplified form of the model is given for extrapolating experimental interface velocity data.
Correlations Between the Structure, Energy and Diffusivity of Grain and Interphase Boundaries
Authors: Muschik T. , Gust W. , Predel B. , Wolf U. , Gumbsch P. , Sommer J. , Herzig C.
Published: March 2011

The paper illustrates the benefits of a combined use of computer simulations of interfacial properties and experiments performed on macroscopic, well-defined bicrystals. The results from two studies are reported. Relative energies of inclined Cu Σ3 grain boundaries were determined by thermal grooving experiments on diffusion-bonded Cu bicrystals. A comparison with calculated energies for crystallographically identical interfaces points to the possibility of macrofaceting of inclined grain boundaries upon annealing. Grain boundary entropy effects are discussed as another possible reason for small differences between theory and experiment. The diffusion rate of Ag* radiotracer in heterophase boundaries of diffusion-bonded Ag-Cu bicrystals can qualitatively be correlated with computed structural details of crystallographically identical Ag-Cu and Ag-Ni phase boundaries. The (computed) site-to-site variation of vacancy formation enthalpy on the (110) phase boundary leads to an anisotropy of Ag* phase boundary diffusion.