bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Characterization of PbO Films Grown by Pulsed Laser Deposition.
Authors: Zabinski J.S. , Donley M.S. , Dyhouse V.J. , Moore R. , McDevitt N.T. 
Published: March 2011

AbstractLead monoxide (PbO) is a potential solid lubricant for use at elevated temperatures in oxidizing environments. The objective of this research was to grow thin films of PbO by Pulsed Laser Deposition (PLD). Film stoichiometry, crystallinity, and chemistry were adjusted by varying substrate temperature and O2 partial pressure during deposition and the effects of changes in film properties on friction coefficients and wear lives were investigated. Chemistry and crystallinity were evaluated using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and glancing angle X-ray diffraction (XRD). Friction coefficients and wear lives were measured in dry nitrogen and at room temperature using a ball-on-flat tribometer. Films deposited at room temperature retained the crystal structure of the target material, but were oxygen deficient. The O/Pb ratio was increased by raising the O2 partial pressure and by increasing the substrate temperature during deposition; the crystal structure and orientation changed with stoichiometry. Friction coefficients ranged from 0.20 - 0.45 and the wear lives were typically less than those obtained from MoS2 films.
In SituCharacterization of the Pulsed Laser DepositIon of Magnetic Thin Films
Authors: Paul A.J. , Bonnell D.W. , Hastie J.W. , Schenck P.K. , Shull R.D. , Ritter J.J. 
Published: March 2011

AbstractPulsed Laser Deposition (PLD) has been proven as an effective means of depositing films from refractory targets. In our earlier work, either Nd/YAG or excimer lasers, interacting directly with target surfaces, were used to deposit thin films of high Tcsuperconductors, high dielectric constant BaTiO3and ferroelectric PbZr0.53Ti0.47O3(PZT). Time-resolved molecular beam mass spectrometry and optical emission spectroscopic techniques have been developed to characterize the vapor plumes responsible for film formation. More recently, this work has been extended to the PLD of magnetic thin films of Ag- Fe3O4nanocomposites using excimer (ArF*, 193 nm) laser excitation. Optical emission spectra of the excited vapor phase species, formed during the plume generation and material deposition process, indicate that physically compressed powdered metal targets have inadequate homogeneity for film production, compared to targets that are chemically produced. Anin situLaser-induced Vaporization Mass Spectrometry (LVMS) technique utilizing a Nd/YAG (1064 nm) laser has been used to determine Time of-Arrival (TOA) profiles of the atomic, molecular, and ionic species produced in the plumes of Ag-Fe3O4. The neutral species TOA profiles indicate velocity distributions that are multimodal and not Maxwellian. These observations are in contrast to the TOA profiles observed from one-component targets (Ag or Fe3O4), where a single Maxwellian velocity distribution is found. Mössbauer effect measurements of the thin films have been made for correlation with the gas phase studies.
High Damage Threshold Optical Films for Excimer Lasers
Authors: Ito H. , Kajita N. , Minowa Y. , Yoshida H. , Ina T. 
Published: March 2011

AbstractHigh damage threshold coating for high energy KrF excimer laser has been developed by the multiple ion beam deposition system, which contains a couple of the ionized cluster beam (ICB) sources and the ionized gas beam source. The damage threshold of low refractive SiO2, high refractive A12O3 and SiO2/A12O3 multilayer coatings is found to be more than 105 shots at 8J/cm2 laser energy. Oxidation is enhanced by ion bombardment during the film growth.The refractive indices of SiO2 and A1203 films were 1.46 and 1.62 at the ion current density of 0.8μA/cm2. The film density of SiOx approaches to the bulk SiO2 of 2.3Og/cm3 with increasing ion current density. The stress-free SiO2 film can be obtained at the ion current density of around 0.5 μA/cm2.
Photoablation Studies of Polymers, Quartz, and Semiconductors with Vacuum Ultraviolet Laser Radiation
Authors: Herman Peter R. , Chen Boyi , Moore David J. , Canaga-Retnam Mark 
Published: March 2011

AbstractExcimer lasers sources of 193nm and 157 nm wavelength were used to obtain new photoablation etching rates for several materials of interest to the microelectronics industry. The harder 157nm radiation provided lower ablation rates and smaller threshold fluences for Polyimide and Polymethyl Methacrylate (PMMA) than with 193nm. For normally robust materials like quartz and Teflon (PTFE), the 157nm laser produced clean and smooth ablation sites with low threshold fluences of 620mJ/cm2 and 68mJ/cm2, respectively, features impossible to obtain with conventional excimer lasers at longer wavelengths. The data should help define new micromachining applications of these two materials for the electronic, optical or medical industry. Results are also reported for GaAs and InP based materials which are found to undergo moderate etch rates of 30-80nm/pulse at fluences of ∼3J/cm2, but suffer thermal damage and material segregation due to surface melting.
Simultaneous Fabrication of Insulator and Contact Holes by Excimer Laser
Authors: Aomori S. , Murahara M. 
Published: March 2011

AbstractA SiO2 insulator and contact holes were simultaneously fabricated at room temperature by ArF and KrF excimer lasers. In this method, NF3 and O2 gases were employed for the reaction gas. When the ArF laser beam irradiated the NF3 and O2 gases in the presence of Si, SiFn and NO2 were produced by photo-chemical reaction. The SiFn adsorbed on the Si substrate pulled out O atoms from the NO2 to form a SiO2 layer. At the same time, the patterned KrF laser beam projected on the substrate and ablated the part exposed to fabricate contact holes. As the results, the simultaneous fabrication of SiO2 insulator with the 700 Å film thickness and selective pattern with the 10 μm width was demonstrated.
Critical Behavior of Interfaces: Roughening and Wetting Phenomena
Authors: Lipowsky Reinhard , Grotehans Stefan , Schmidt Götz J.O. 
Published: March 2011

ABSTRACTThe critical behavior of interfaces is discussed from a theoretical point of view. Two classes of critical phenomena will be considered: (i) Roughening phenomena related to changes in the interfacial morphology; and (ii) Wetting phenomena related to changes in the interfacial structure. In two dimensions, the critical behavior can be determined exactly for a variety of models. As a result, one obtains different universality classes depending on the nature of the inter molecular forces.
Determination of the Width of the Single Phase Stability Field of Nickel Titanate Spinel
Authors: Anderson Ian M. , Barry Carter C. 
Published: March 2011

ABSTRACTThe width of the single-phase stability field of nickel titanate spinel (Ni2(1+x)Ti1−xO4) has been determined in order to resolve an ambiguity in the analysis of the microstructure of equilibrated and quenched spinel-containing specimens. Bulk polycrystalline diffusion couples of the constituent oxides, NiO and NiTiO3, have been prepared at several reaction temperatures between 1400°C and 1550°C. The microstructure of the reaction layers of slow-cooled specimens has been examined by SEM and the composition has been mapped using x-ray microanalysis. It is concluded that the nickel titanate spinel phase has a narrow range of stability, and that the stoichiometry of the spinel is temperature dependent. The microstructure of equilibrated and quenched specimens is discussed in light of these findings.
Blister-Promoted Bubble Growth in Viscous Polymer Melts
Authors: Albalák Ramon J. , Tadmor Zehev , Talmon Yeshayahu 
Published: March 2011

ABSTRACTResidual monomer and other low molecular weight volatile components are removed from polymer melts in a devolatilization step involving bubble formation and growth. Polymer strands containing residual volatiles were extruded into a heated and evacuated devolatilization tank and were then frozen by the flow of cooling water. They were subsequently fractured in liquid nitrogen to reveal their cross-sections and examined in a scanning electron microscope (SEM).SEM observations revealed a previously unknown growth phenomenon in which devolatilization was seen to proceed through a ‘blistering’ mechanism. We discovered that volatile bubbles growing in the melt are fed by the formation of blisters on their inner surfaces. These blisters are formed by the coalescence of a growing bubble and the many satellite micro-bubbles formed around it as it expands. We propose a general mechanism for bubble growth in which we have shown that heterogeneous bubble nucleation in the core, which is governed by the degree of superheat, plays a major role in determining the overall rate of devolatilization. Tensile stresses accompanying bubble growth may result in a local increase in superheat by reducing the local pressure in the melt. This additional superheat combined with the possible accumulation of impurities on the macrobubble surface may be sufficient to increase the nucleation rate of microbubbles in the melt adjacent to the growing bubble, resulting in the large number of blisters formed on the bubble surface.
Domain Structures and Phase Transitions in Langmuir Monolayers
Authors: Qiu Xia , Ruiz-Garcia Jaime , Knobler Charles M. 
Published: March 2011

ABSTRACTA variety of recent measurements has shown that the phase diagrams of Langmuir monolayers of relatively simple amphiphiles such as fatty acids and their methyl and ethyl esters are remarkably complex. Nine condensed phases have been identified; their structures can be related to those of known smectic phases. A key distinction between phases is the orientation of the molecular tilt azimuth with respect to the local hexagonal order of the head groups. When monolayers are examined by fluorescence microscopy, regions of uniform tilt can be observed if the exciting radiation is polarized with respect to the surface normal. The tilt regions form patterns similar to those observed in freely suspended films of smectic liquid crystals. The patterns can be changed by compressing the film and by changing the temperature. Transitions between different phases can be observed.
X-Ray Scattering Studies of Multilayer Interfaces
Authors: Sanyal M. K. , Sinha S. K. , Gibaud A. , Satija S. K. , Majkrzak C. F. , Homma H. 
Published: March 2011

AbstractThe results of specular and diffuse x-ray scattering studies of multilayers are discussed. We show here that such studies can yield detailed statistical information about the interfacial roughness and morphology. Results on a GaAs/AlAs multilayer are presented and the data is analyzed within the Born approximation.
High Resolution Leed Study of The Fe Growth Mode on Cu(100), Cu(110) and Cu (111) Surfaces
Authors: Cao Yuqun , Montano Pedro A. 
Published: March 2011

ABSTRACTWe have investigated the growth mode of iron on clean Cu(100), Cu (110) and Cu(111) surfaces using high resolution LEED. We studied the effect of substrate temperature on the growth of epitaxial fee iron. Iron metal was evaporated from an electron beam source under UHV conditions and deposited on the copper single crystal surfaces at three different temperatures (173 K, 300 K and 473 K). A high resolution LEED system was used to measure the diffraction spot profiles. The samples were studied as a function of temperature after deposition on the copper substrates. The clean Cu surfaces were also measured and used as references for the Fe:Cu system. The diffraction spot profiles show Gaussian line shape before and after the Fe deposition. The effect of iron grown on the Cu surface is to reduce the coherent length. This effect is observed for all the copper surfaces. The intensity of the diffraction spots exhibit a sudden increase above 470 K, simultaneously a larger coherent length is observed. This effect occurs for all copper surfaces. The epitaxial growth of Fe is better on Cu (100) than on the other surfaces. The best epitaxial growth is obtained for the highest substrate temperature. A careful Auger study reveals that the anomalous increase observed on the intensity of the diffraction spots is related to the evaporation of iron from the copper surface. The spot profiles at low temperature are very broad and are suggestive of very poor epitaxy, random islands growth with a high probability of bec iron inclusions.
Epitaxial Growth of GaAs-AIGaAs Quantum Wire Superlattices on Vicinal Surfaces.
Authors: Petroff P. M. , Krishnamurthy M. , Wassermeier M. , Miller M. , Weman H. , Kroemer H. , Merz J. 
Published: March 2011

ABSTRACTThis paper reviews the problems that are generic to the direct epitaxy of quantum wire superlattices on {100} and {110} vicinal surfaces using molecular beam epitaxy.
Dynamics of Microstructure in the Early Stages of Ion Beam Assisted Film Growth
Authors: Atwater Harry A. , Tsai C. J. , Nikzad S. , Murty M.V.R. 
Published: March 2011

ABSTRACTRecent progress in low energy ion-surface interactions, and the early stages of ion-assisted epitaxy of semiconductor thin films is described. Advances in three areas are discussed: dynamics of displacements and defect incorporation, nucleation mechanisms, and the use of ion bombardment to modify epitaxial growth kinetics in atrulysurface-selective manner.
High–Resolution Low Energy Electron Diffraction Study of Surface Instabilities and Growth Dynamics
Authors: Yang H.-N. , Zuot J.-K. , Fang K. , Lu T.-M. , Wang G.-C. 
Published: March 2011

ABSTRACTRecent advances in high–resolution low–energy electron diffraction (HRLEED) techniques have led to a new capability which provides both very high spatial and temporal resolutions to probe quantitatively the equilibrium and dynamical processes that occur on surfaces and growth fronts. These techniques are especially powerful when the surface or growth front contains atomic steps. Different distributions of steps give different surface atomic pair correlation functions and therefore different angular profile shapes in the diffraction pattern. Recent examples of quantitative HRLEED study of low index plane equilibrium roughening and preroughening transitions are presented. In the growth dynamics, both two–level and multilevel step structures are considered. Examples of the measurements of growth exponents and dynamics scaling are presented.
Interfacial Stability of CoSi2/Si Structures Grown by Molecular Beam Epitaxy
Authors: George T. , Fathauer R. W. 
Published: March 2011

ABSTRACTThe stability of CoSi2/Si interfaces was examined in this study using columnar suicide structures grown on (111) Si substrates. In the first set of experiments, Co and Si were co-deposited (1:7 flux ratio) using molecular beam epitaxy at 800°C and the resulting columnar suicide layer was capped by epitaxial Si. Deposition of Co on the surface of the Si capping layer at 800°C results in the growth of the buried suicide columns. The buried columns grow by subsurface diffusion of the deposited Co, suppressing the formation of surface islands of CoSi2. The columns' sidewalls appear to be less stable than the top and bottom interfaces, resulting in preferential lateral growth and ultimately in the coalescence of the columns to form a continuous buried CoSi2 layer.In the second set of experiments, annealing of a 250nm-thick buried columnar layer at 1000°C under a 100nm-thick Si capping layer results in the formation of a surface layer of CoSi2 with a reduction in the sizes of the CoSi2 columns. For a sample having a thicker (500nm) Si capping layer the annealing leads to Ostwald ripening producing buried equiaxed columns. The' high CoSi2/Si interfacial strain could provide the driving force for the observed behavior of the buried columns under high-temperature annealing.
Novel Epitaxial Growth and Surface Order-Disorder Transitions of CU3AU(110) and CU3AU(111)
Authors: Huang J.C.A. , Dura J. A. , Flynn C. P. 
Published: March 2011

AbstractWe report the results of a reflection high energy electron diffraction (RHEED) study on the order-disorder transitions at the (111) and (110) surface of Cu3Au. Our Cu3Au films were epitaxially grown on sapphire substrates with bcc (Nb or Mo-Cr) buffer layers. The (111) and (110) surfaces of Cu3Au are atomically flat as indicated by the RHEED patterns. We use the normalized integrated intensity of the superstructure streaks to measure the long range order parameter. We observed that the surface layers of both (110) and (111) Cu3Au exhibit an apparently continuous order-disorder transition, close to that predicted by mean field theory [5]. The kinetics of surface ordering also were monitored by RHEED after initial deposition of disordered layers, 2 MLs thick, on the ordered Cu3Au templates. In studies of the surface reordering process we find that the RHEED pattern is almost entirely sensitive to the surface layer alone.
Initial Stages of Deposition-Concurrent Surface Segregation in Fe/Au Epitaxial Multilayers on GaAs(001)
Authors: Sano Ken-Ichi , Miyagawa Tsugio 
Published: March 2011

ABSTRACTRHEED and AES studies showed deposition-concurrent surface segregation (DCSS) consists of two stages: an initial and a continuous segregation stage. The dominant terms of the enthalpies of DCSS were shown to be the difference between the surface energies of the film and the substrate material.
Epitaxial YBa2Cu3O7−x Thin Films: Scanning Tunneling Microscope Study of the Initial Stages of Epitaxial Growth, Growth Mechanism, and Effects of Substrate Temperature
Authors: Zhu Shen , Lowndes Douglas H. , Zheng X.-Y. , Norton David P. , Warmack R. J. 
Published: March 2011

ABSTRACTThe surface microstructure of epitaxial YBa2Cu3O7−x films grown by pulsed laser ablation on (001) MgO and SrTiO3 substrates has been studied at various growth stages, ranging in thickness from eight c-axis perpendicular unit cells to ∼220 nm. On MgO (lattice mismatch ∼9%) even the thinnest films grow unit cell-by-unit cell by an island growth mechanism. However, on SrTi03 (mismatch ∼1%), a transition from a layer-like growth mode to island growth is observed as the film thickness increases. Islands with clear spiral growth structures are observed in even the thinnest films on MgO, but for films grown on SrTiO3 the spiral growth features are found only for film thicknesses slightly greater than the critical thickness for the switch to an island growth mode. The islands consist of stacks of atomically flat terraces whose step heights are multiples of the c-axis lattice parameter. The island density decreases significantly with increasing film thickness, while their diameters range from 50–400 nm, increasing with growth temperature. The terraced island grain morphology causes a surface roughness of from 10 to 30 nm (depending on growth temperature) in films ∼200 nm thick.
Smoothing Effects of MOCVD Grown GaAs/AlxGa1−xAs Superlattices
Authors: Xu Xian-gang , Huang Bai-biao , Liu Shi-wen , Ren Hong-wen , Jiang Min-hua 
Published: March 2011

ABSTRACTGaAs/AlxGa1-xAs (x=0.5, 0.6, 1.0) superlattices used as buffer layers in HEMT devices have been grown by Metalorganic Chemical Vapor Deposition (MOCVD) at. atmospheric pressure, and characterized by cross-sectional transmission electron microscopy (XTEM). The initial stage of nucleation on the substrates has been clearly verified by examining the undulations of a 30na GaAs layer sandwiched between the substrate and the superlattice. Both Alo.5Gao.5As/GaAs and AlAs/GaAs superlattices can smooth out interface roughness caused by contaminations and dislocations on the substrate surface. The mechanism of smoothing effect has been discussed in detail.
Real Time Ellipsometry Study of the Interfaces Formation of Microcrystalline Silicon
Authors: Fang M. , Drevillon B. 
Published: March 2011

ABSTRACTA detailed study by real time spectroellipsometry of the early stage of the growth of microcrystalline silicon (μc-Si) on various substrates is presented. In practical applications μc-Si films are generally deposited on hydrogenated amorphous silicon (a-Si:H) or on transparent conducting oxides (TCO). In the case of a-Si:H, the beginning of the deposition is described by an uniform growth of a 60 Å thick porous μc-Si. However a nucleation-coalescence mechanism is observed during the growth of the first 60–70 Å thick μc-Si on smooth crystalline silicon (c-Si) substrate. In contrast a strong chemical reduction of the TCO substrates is observed during the first 10–20s of the exposure to the hydrogen diluted plasma. Then the ellipsometric measurements reveal an induction period of 30–60 s for the nucleation of microcrystallites. The influence of the preparation conditions of μc-Si on the TCO / μc-Si interfaces formation is emphasized.
In-Situ, Time Resolved, Kinetics of Reactions in Co-Ge thin Films
Authors: Walser R. M. , Lee Byung-Hak , Valanju Alaka , Win Winston , Becker M. F. 
Published: March 2011

ABSTRACTWe report the first kinetic study of metal-semiconductor interface reactions using in-situ, time resolved, laser interferometry. Diffusion couples with Co/Ge thicknesses of 1500 Å/1500 Å were sputter deposited on silicon wafers, and vacuum-annealed at temperatures between 300°C-400°C. Under these conditions polycrystalline CoGe was expected to form [1]. Real time laser (HeNe 6328 Å) interferograms for each anneal were recorded in-situ. These data were supplemented by information from AES and X-ray.For temperatures below 400°C the diffusion controlled formation of CoGe was observed. The composition was confirmed by Auger depth profiling that showed uniform Co and Ge concentrations when the reaction went to completion. The well defined interferences fringes were formed by the dissolution of amorphous Ge. The activation energy = 1.6 eV for the formation of CoGe were determined with precision from the temperature dependence of the time required to anneal the fixed λ/4 distance between adjacent minima and maxima of the interferogram. We discuss the evidence for formation of an intermediate Co-rich compound following the initial diffusion of Co into Ge. The results of these experiments indicate that optical interferometry will be a valuable adjunct to other techniques used to study metal-semiconductor interface reactions.
Phase Separation Kinetics of Binary Systems: Effects of Hydrodynamic Interaction And Surfactants
Authors: Kawasaki Kyozi , Koga Tsuyoshi , Kawakatsu Toshihiro 
Published: March 2011

ABSTRACTCell dynamics computer simulation method is used to investigate effects of hydro-dynamic interaction as well as effects of added surfactants on phase separation kinetics. In the former the obtained scattering structure function for 3-dimensional system reproduces the experimental results for polymer blends remarkably well. In the latter we display self-assembling process in two-dimensional system on computer.
Point Defect Detector Studies of Oxidized Silicon
Authors: Meng H. L. , Jones K. S. , Prussin S. 
Published: March 2011

ABSTRACTIon implantation and thermal oxidation are device fabrication processes that lead to perturbation of equilibrium point defects concentration in silicon. This study investigates the interaction between oxidation-induced point defects and type II dislocation loops intentionally introduced in silicon via ion implantation. The type II dislocation loops were introduced via Si implants into (100) Si wafers at 50 keV to a dose ranging from 2×1015 to 1×1016/cm2. The subsequent furnace annealing at 900 °C was done for times between 30 min and 4 hr in either a dry oxygen or nitrogen ambient. Plan-view transmission electron microscopy (PTEM) was used to characterize the increase in atom concentration bound by dislocation loops as a result of oxidation. The results show type II dislocation loops can be used as point defect detector and they are efficient in measuring oxidation-induced point defects. It is also shown that the measured net interstitials flux trapped by dislocation loops is linearly proportional to the total supersaturation of interstitials as measured by oxidation enhanced diffusion (OED) studies.