bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Dynamics Simulations and Experimental Evidence for Deep Penetration by Channeled Ions During Low-Energy Ion Bombardment of III-V Semiconductors
Authors: Stoffel N.G. , Schwarz S.A. , Pudensi M.A.A. , Kash K. , Florez L.T. , Harbison J.P. , Wilkens B.J.
Published: March 2011

Molecular dynamics simulations are used to investigate the formation of deep crystalline damage during the low-energy ion bombardment of semiconductor crystals. The trajectories of primary ions are calculated as they propagated through a model crystal lattice. Energy losses by nuclear recoil and and by electronic excitation are included. For beams of heavy ions at energies below 1 keV, the average penetration range of the simulated trajectories is only a few nanometers. However, a small, but, significant fraction of the ions are found to scatter into <011= axial channels through which they propagate tens of nm below the surface. This effect is used to explain high-resolution secondary ion mass spectrometry and photoluminescence data which reveal deep ion penetration and optical damage on the same length scale. Our results suggest that unintentional ion channeling is a major factor in the extensive degradation of optical and electrical properties of semiconductor surfaces which are exposed to low energy ion bombardment during device fabrication.
Influence of Energy Deposited by Energetic Particle Bombardment on thin Film Characteristics
Authors: Winters Harold F. , Eckstein W. , Coufal H.J.
Published: March 2011

It has been recognized since the 1960's that bombardment of a growing thin film by energetic particles strongly influences film properties. Particle bombardment has generally been accomplished by accelerating ions into the growing film. However, it has also been recognized since the 1960's that energetic particles reflected from the target influence the characteristics of films grown by physical sputtering and many experiments have been interpreted on this basis. A systematic study of the energy reflected from the surface by normally incident, singly charged noble-gas ions on five substrates of different masses has recently been published. This data along with sputter yields from the literature allow estimates to be made which were previously unavailable. The energy reflected from the target is carried away by electrons, sputtered particles and reflected ions (neutrals). The purpose of this paper is to provide basic information which will allow thin film scientists to estimate the influence of various experimental parameters on the amount of energy arriving at the growing film. The energy reflected from the target per sputtered atom will be given as a function of ion mass, target mass, and ion energy. TRIM.SP Monte Carlo calculations will be used to estimate the ratio of the energy carried away by sputtered atoms to that carried away by reflected ions. Calculations will also be used to estimate the average energy of the sputtered atoms as a function of ion mass, substrate mass and ion energy. It will be shown how this information can be used to guide the adjustment of experimental parameters in sputtering environments so as to control film characteristics.
Laser-Induced Dry Etching of GaAs with High Aspect Ratio
Authors: Lee Cheon , Sayama Hirokazu , Namba Susumu , Takai Mikio
Published: March 2011

Laser-induced thermochemical reactions have been investigated for GaAs in a CCl2F2 gas ambient using an argon-ion laser. The chemical compositions of the reaction products deposited on the etched groove were measured by Auger electron spectroscopy (AES). The conditions of laser power, scan speed, and CC12F2 gas pressure under which the etching reaction occurs without deposition of the residue were clarified. High etching rates up to 267 μm/s and an aspect ratio of 4.5 have been achieved by a single scan of a laser beam. Microprobe photoluminescence and Raman scattering measurement were carried out on the etched surface to characterize damage induced by this processing.
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

Lead 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

Pulsed 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

High 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

Excimer 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

A 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

The 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

The 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

Residual 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

A 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.
Polydiacetylene Monolayers: Model Systems for Enzymatic Surface Modification
Authors: Wilson Troy E. , Bednarski Mark D.
Published: March 2011

We are exploring the requirements for enzyme-catalyzed reactions on small molecules tethered to the surfaces of organic monolayers. Despite considerable effort toward understanding enzymatic processes in solution1, the chemistry of enzymes at interfaces has not been studied. Increasingly sophisticated methods of surface modification, including self-assembly2 and photolithographic3 techniques, raise intriguing prospects for enzymatic surface chemistry. This paper describes our initial investigations of the proteolysis of a dipeptide substrate covalently tethered to the surface of a polydiacetylene film using the enzyme, subtilisin BPN'.
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

The 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

We 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

This 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

Recent 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

Recent 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

The 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

We 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

RHEED 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

The 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

GaAs/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

A 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

We 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

Cell 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

Ion 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.
Microstructural Behavior of Poly-Si Implanted with Oxygen
Authors: David Theodore N. , Huang WenLing M. , Crozier Peter A.
Published: March 2011

Poly-Si layers are used for various applications in integrated-circuit manufacturing technology. In most cases, the microstructure of the layers can have a significant impact on performance of the structures. In the present study, poly-Si layers implanted with 1E14 and 1E16 oxygen cm-2 were characterized using transmission electron-microscopy (TEM). Layers implanted with 1E16 cm-2 oxygen had exhibited lower variations in sheet-resistance for a given variation in post-implant anneal temperature. The microstructural behavior of the films was therefore of interest. TEM characterization showed differences in the microstructure of poly-Si implanted with 1E14 and 1E16 oxygen cm-2. Layers implanted with 1E14 doses showed a columnar grain-structure similar to as-deposited poly-Si layers. Grain-sizes were quite uniform and relatively small. Layers implanted with 1E16 doses showed a strongly defected grain-structure quite different from as-deposited poly-Si layers. The columnar structure had been largely destroyed. Grain-sizes were less uniform, with primarily large grains but also small grains being present. There are indications that the 1E16 samples had been amorphized by the implant and recrystallized by the anneal, but it is not clear from these samples whether this is the cause for the variation in resistance-behavior (between IE 14 and IE 16 samples). TEM micrographs are indicative of the presence of oxygen-bubbles in both sets of implanted specimens. The bubbles arise due to the oxygen implant. There is no noticeable correlation between poly-Si grain-boundaries and the bubbles.
The Structure and Properties of Grain Boundaries in Ni3Al
Authors: Mills M. J. , Goods S. H. , Foiles S. M.
Published: March 2011

The mechanical behavior of polycrystalline intermetallic compounds are often strongly influenced by the properties of the interfaces present. A classic example of this is the intergranular fracture exhibited by polycrystalline Ni3Al, and the dramatic increase in ductility upon the addition of small amounts of boron. It has been proposed that boron may promote the transmission of slip across grain boundaries by inducing the formation of a local region of compositional disorder. The results of experimental efforts to characterize the effect of boron on the structure and chemistry of these grain boundaries are summarized. Recent high resolution transmission electron microscopy studies using oriented bicrystals are described which indicate that there is no apparent change in the compositional ordering to within 0.5 nm from the boundary. These experimental results are compared with the results of atomistic calculations which have been used to examine the effect of stoichiometry and boron content on the energy and degree of ordering of these boundaries. The proposed mechanisms of intergranular fracture in Ni3Al are discussed based on this experimental and theoretical work.
Phase Transitions at Internal Interfaces
Authors: Rottman Craig
Published: March 2011

Interfaces often undergo phase transitions even though nothing special is happening to the bulk solid. These transitions are possible in any internal interface, such as a grain boundary, an interphase boundary, a stacking fault, or an antiphase boundary. As for bulk solids, interface transitions may be defined from a thermodynamic point of view. When distinct interfacial phases coexist, interfacial phase diagrams are useful in visualizing thermodynamic data. Various classes of these transitions will be discussed in general and then illustrated with examples from recent work on models and experimental systems.
Atomic Structure of the SnO2(110) Surface
Authors: Godin T. J. , Lafemina John P.
Published: March 2011

Using a tight-binding, total-energy model, we examine atomic relaxations of the ideal stoichiometric and reduced tin oxide (110) surfaces. In both cases we find a nearly bond-length conserving rumple of the top layer, and a smaller counter-relaxation of the second layer. These calculations show no evidence of surface states in the band gap for either surface.
Grain-Boundary-Mediated Failure in Polycrystals
Authors: Nichols C. S. , Smith D. A.
Published: March 2011

It is well known that the atomic structure of an interface has some influence on its properties and thus on the properties of a poly crystalline ensemble as a whole. However, with the enormously large number of interface structures possible and no cohesive framework within which to understand them, it seems a hopeless task to search for structure-property relationships for all interfaces. Rather, we have adopted the viewpoint that interfaces may be grossly categorized into low-misorientation angle/special boundaries and random boundaries with a subsequent two-state division in their properties. We will discuss a simple methodology for examining stress-voiding and electromigration failures in thin metallic interconnects that takes the differing abilities of the interface classes to contribute to failure into account. We thus provide one of the first attempts to account consistently for the atomic structure of an interface and the macroscopic behavior observed in a poly crystalline system.
Hydrogen Segregation To Interfaces
Authors: Marwick A. D. , Liu Joyce C. , Krakow W. , Thompson R. D.
Published: March 2011

In order to achieve a better understanding of hydrogen segregation to interfaces, a combination of techniques is being used in which hydrogen is deliberately introduced into planar interfaces between thin films, then the segregation measured using highenergy ion-beam profiling techniques. Results are given for heterophase interfaces produced by epitaxial deposition on silicon: The AI/Si (111) and CoSi2/Si (001) interfaces. A preliminary study of Au tilt boundaries in thin-film bicrystals shows the presence of a large amount of hydrogen, ∼1016 atoms/cm2, in the boundary after plasma hydrogenation, but also the presence of C impurity (∼ 1.6 × 1015 atoms/cm2 ) and Ag. We conclude that some of the hydrogen in the boundary may have been chemically bound to the carbon.
An Atom Probe Field Ion Microscope Investigation Of The Role Of Boron In Precipitates And At Grain Boundaries In NiAl
Authors: Jayaram Raman , Miller M. K.
Published: March 2011

The high resolution analytical technique of Atom Probe Field Ion Microscopy (APFTM) haseen used to characterize grain boundaries and the matrix of a stoichiometric NiAl alloy doped with 0.04 (100 wppm) and 0.12 at. % (300 wppm) boron. Field ion images revealed boron segregation to the grain boundaries. Atom probe elemental analysis of the grain boundaries measured a boron coverage of up to 30% of a monolayer. Extensive atom probe analyses also revealed a fine dispersion of nanoscale boride precipitates in the matrix. The boron segregation to the grain boundaries was found to correlate with the observed suppression of intergranular fracture. However, the decrease in ductility of boron-doped NiAl is attributed in part to the precipitation hardening effect of the boride phases.
Environment Sensitive Embedding Energies of Impurities, and Grain Boundary Relaxation in Iron
Authors: Krasko Genrich L.
Published: March 2011

Impurities, such as H, P, S, B, etc, have a very low solubility in iron, and therefore prefer to segregate at the grain boundaries (GBs). In order to analyze the energetics of the impurities on the iron GB, the LMTO calculations were performed on a simple 8-atom supercel 1 emulating a typical (capped trigonal prism) GB environment. The so-called “environment-sensitive embedding energies” were calculated for H, B, C, N, O, Al, Si, P, and S, as a function of the electron charge density due to the host atoms at the impurity site. It was shown that, at the electron charge density typical of a GB, B and C have the lowest energy among the analyzed impurities, and thus would compete with them for the site on the GB, tending to push the other impurities off the GB. The above energies were then used in a modified Finnis-Sinclair embedded atom approach for calculating the equilibrium interplanar distances in the vicinity of a (111) σ3 tilt GB plane, both for the clean GB and that with an impurity. These distances were found to be oscillating, returning to the equilibrium spacing between (111) planes in bulk BCC iron by the 10th-12th plane off the GB plane. H, B, C, N and O actually dampen the deformation wave (making the oscillation amplitudes less than in the clean GB), while, Al, Si, P and S result in an increase of the oscillations. The effect of B, C, N and O may be interpreted as cohesion enhancement; this conclusion supports our earlier first-principles results [1] on B and C.
Xafs Studies of Cr-Si-O Interfaces with Al and Polyimide by using Synchrotron Radiation
Authors: Ogata Kiyoshi , Nakano Asao , Narizuka Yasunori , Watanabe Takayoshi , Yamazaki Tetsuya
Published: March 2011

The structure change of a Cr-Si-O thin film with regard to heat-treatment was investigated not only by the transmission XAFS method but by the surface sensitive XAFS method using synchrotron radiation. As a result of transmission XAFS, the Cr-Si-O thin film as sputtered has an amorphous structure like a mixture of SiO2, Cr and CrSix. After heat-treatment to 650 K, Si-Cr bonds decreased and Si-O and Cr-Cr bonds increased. CrSix is unstable in the system. The interfacial studies by the surface XAFS method showed i) at the interface with polyimide, there is a thin layer which is dominantly made of Cr2O3 and ii) at the interface with Al, Cr atoms are mainly coordinated to Cr. Analyses by the XAFS method gave consistent results with chemical analyses by x-ray photoelectron spei roscopy and observation by transmission electron microscopy.
Using Ultrathin-Film, Modulated Composites to Control the Reaction Mechanism of Ternary Compound Formation
Authors: Fister Loreli , Johnson David C.
Published: March 2011

A predictable, controllable approach to the synthesis of ternary compounds through known intermediates is presented. Thin and ultrathin film superlattices were made in the Mo-Se, Cu-Se and Mo-Cu systems. Differential scanning calorimetry, low- and high-angle x-ray diffraction were used to assess the interdiffusion and nucleation reactions between elemental layers in these one-dimensional crystals. The experimental parameter modulation distance was used to influence the interfacial reactions. The results from each binary system were then used to predict the reaction pathway in the synthesis of a ternary compound, Cu2Mo6Se8. Superlattices with two different lengthscales were investigated. In the first, only one intermediate, MoSe2 which typically crystallizes at ∼200'C, is observed prior to the crystallization of Cu2Mo6Se8. In the second, no crystalline intermediates are observed below 6000 C.
Formation And Stability Of Nanocrystalline Nb-Cu Alloys
Authors: Abe Yoshio R. , Holzer J. C. , Johnson W. L.
Published: March 2011

Nanocrystalline Nb100−xCux (0 ≤ x ≤ 30) alloys of 8 – 25 nm grain size are synthesized with the mechanical alloying technique. Differential scanning calorimetry reveals two separate stages of grain growth. In the first stage, the grain growth is associated with migration of solute Cu atoms to grain boundaries. Grain growth stops as the grain boundaries are saturated with Cu. The second reaction takes place either when the threshold for the nucleation of an Fcc Cu phase in the grain boundary is overcome by thermal activation, or when segregating Cu atoms in the grain boundary are driven by diffusion to the growing Cu grains, and the Cu concentration in the grain boundary drops. This increases the grain boundary energy, and initiates a second stage of rapid grain growth.
Interface Electronic And Magnetic Structures Of Layered Fe In Contact With MgO
Authors: Kim Young Keun , McHenry Michael E. , Oliveria Manuel P. , Eberhart Mark E.
Published: March 2011

A model based on the state-of-the-art, first-principles layer Korringa-Kohn-Rostoker (LKKR) method has proven to be very effective in describing the electronic and magnetic structure of metal/ceramic interfaces. We have performed self-consistent field computations incorporating spin polarization both for Fe/MgO superlattice (bulk technique) and for MgO/Fe/MgO sandwich (layer technique) systems. Muffin-tin potentials were employed for both materials in our computations. Iron layer was embedded in MgO, the host material, to have a [110](100)Fe / [100](100)MgO contact configuration. A large enhancement of magnetic moments has been found at the interface.
Hrem Study On The Interfacial Structure In Oxygen-Defective CaMnO3−x System
Authors: Shibahara H. , Taguch H.
Published: March 2011

Electron diffraction and high resolution electron microscope observation for CaMnO3−x (x=0. 02 and 0. 05) showed unique features of the ordered structure. A coherent intergrowth of several phases with a long period in CaMnO3−x composed of extended perovekite units was observed. The relation in crystallography in the family of ordered perovskite related oxides in CaMnO3−x, which could help towards an understanding of magnetic properties and catalytic action of CaMnO3−x, is discussed.
High Resolution Electron Microscopy Studies On The Microstructure Of β-Si3N4w/Al Interfaces In A β-Si3N4w/6061Al Composite
Authors: Ning X. G. , Pan J. , Hu K. Y. , Ye H. Q.
Published: March 2011

The whisker/matrix interfaces in a β-Si3N4w/60 61Al composite were structurally characterized by high resolution transmission electron microscopy (HRTEM). It was shown that there was a nearly amorphous layer (2–3 nm thickness) at a whisker/matrix interface. The magnesium segregation at the whisker/Al interface was revealed by electron dispersive analysis of x-ray (EDAX). MgO and MgAl2O4 nanocrystal particles were formed at the whisker/matrix interface due to the Mg segregation there during the manufacturing of the composite. The Mg2Si particles preferred to precipitate at the whisker/Al interface when the composite was processed with T6 heating treatment. There were specific orientation relationship of the MgAl2O4 or Mg2Si particles with the β-Si3N4 whiskers.
Study Of Interfaces In XDTM Al/TiCp Metal Matrix Composites
Authors: Mitra R. , Chiou W. A. , Weertman J. R. , Fine M. E. , Aikin R. M.
Published: March 2011

The metal-ceramic interface in an XDTM Al/TiCp metal matrix composite has been characterized in as-extruded, recrystallized, and high temperature heat-treated conditions. In both the as-extruded and recrystallized composite, the interface is atomically abrupt. Localized orientation relationships exist between Al and Tic that lead to some degree of coherency at the interface. Recrystallization produces semicoherent interfaces by formation of subgrains in the Al adjacent to the Tie particles. Few interfaces show cracking, even after extensive deformation. Lack of cracking together with the direct contact down to atomic level, observed between the two phases are evidence for excellent bonding between the carbide particles and the aluminum matrix. Heat treating samples at 913 k for 24 hours produces reaction products like Al3Ti and Al4C3. These reactions are explained on the basis of thermodynamic data.
Interface And Near-Interface Microstructure Of Discontinuous Reinforced Metal Matrix Composites
Authors: Lucas James P. , Yang Nancy Y. C. , Stephens John J.
Published: March 2011

Interfacial microstructure can have a significant influence on the microfracture processes of discontinuous reinforced metal matrix composites (DMMCs). The fracture properties, however, are largely influenced by the microfracture and deformation mechanisms associated with the matrix microstructure and with the interface microstructure. Also, it is known that the paniculate morphology and distribution can modify the deformation process by influencing the stress state that develops in the matrix materials near the reinforcement. Along with the matrix microstructure, characterizing the role of the interfacial and the near-interfacial microstructure is essential for a broader understanding of fracture behavior in DMMCs. To characterize the microstructure of cast DMMCs, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron microprobe (EMP) examinations were conducted at the interface and in regions near the particulate/matrix interface. Materials studied consisted of cast Al-4.5Cu and Al-7Si matrix alloy systems with B4C and SiC reinforcement. In general, the interfacial and matrix microstructure of Al-4.5Cu/SiC and Al-4.5 CuB4C composites exhibited little variance, i.e. the reinforcement type had no apparent effect on the resultant microstructures. For the Al-7Si system, however, significant microstructural variance was observed both in the matrix and interfacial regions. In the Al-7Si/B4C composite, an extensive reaction zone was found at the B4C interface. Interfacial compounds observed in Al-7SiC/B4C were Ti(O,B), Si, and MgB6 precipitates. In the near-interface region compounds such as Alx(B, C, 0)y, AlxMg(1−x)B2, and Al4C3 were found. In sharp contrast to Al-7SiC/B4C, an extensive interfacial reaction zone was not revealed for Al-7Si/SiC MMC. Only isolated, extremely fine second phase precipitates were observed on SiC paniculate interfaces. Fracture surface evidence suggested that both the matrix and the interface microstructure influenced deformation and microfracture mechanisms in DMMCs.
Lomer Dislocations in (0 0 1) GaSb/GaAs Heterostructure.
Authors: Rocherj André M. , Kang Joon M. , Ponchet Anne
Published: March 2011

The (001) GaSb/GaAs heterostructure reveals a nearly complete relaxation of the misfit strain. This relaxation is connected to the highly regular network of Lomer dislocations which is a consequence of island growth conditions.
Stress and Microstructure in Lpcvd Polycrystalline Silicon Films: Experimental Results and Closed Form Modeling of Stresses
Authors: Krulevitch P. , Johnson G. C. , Howe R. T.
Published: March 2011

Characterization of undoped polycrystalline silicon films indicates that correlations exist between stress and microstructure. Films of thickness between 0.5–3.6 μm were deposited onto SiO2-covered single crystal silicon wafers between 605 and 700°C using low pressure chemical vapor deposition (LPCVD). The average in-plane film stress and the stress gradient through the film thickness were determined from wafer curvature measurements, and film microstructure was studied with cross-sectional TEM. Films deposited near 605°C exhibit overall tensile stresses that result from an amorphous to crystalline phase change. At deposition temperatures exceeding 630°C, a columnar grain structure evolves out of a transition region of small grains at the SiO2 interface. The columnar films are compressive, with the source of compression linked to the region of small grains. Stress is modeled using a closed form solution ihat considers a linearly elastic contracting ellipsoidal inclusion near the surface of a half space. Several applications of the stress model are discussed.