bluuebunny/crossref_metadata_2025 huggingface dataset:
Optically Induced Paramagnetic Defects in PbTiO3 Single Crystals
Authors: Warren W.L. , Tuttle B.A. , Sun B.N. , Huang Y. , Payne D.A.
Published: March 2011

Optical excitations for trivalent platinum (5d7, t6e) and trivalent Pb (6s1) ions in lead titanate single crystals have been observed for the first time by electron paramagnetic resonance (EPR). The g and hyperfine coupling, A, tensors of Pt+3 defects were found to be axial: gil∥ = 1.938, g⊥ = 2.478, A∥ = 0.0164 cm−1, and A⊥ = 0.0324 cm−1. Analysis of the EPR spectra by crystal field theory indicates that the Pt+3 ions are in tetragonally distorted (elongated) octahedral sites, strongly suggesting that they substitute for the central Ti+4 ions in the perovskite lattice. Axially symmetric Fe+3 impurities were also observed in the crystals, and they also appear to substitute for the Ti+4 cation. Identification of Pb+3 in these single crystals further shows that holes trapped at Pb+2 ions are an inherent feature of Pb-based perovskite ferroelectrics.
Preparation of SrTiO3 Thin Films by Ecr and Thermal Mocvd
Authors: Lesaicherre P-Y. , Yamaguchi H. , Sakuma T. , Miyasaka Y. , Yoshida M. , Ishitani A.
Published: March 2011

SrTiO3 thin films were prepared by ECR and thermal MOCVD. In thermal-CVD mode, Sr content and Ti content were at a maximum at 0.56 Torr. Results showed that SrO deposition is a surface reaction limited process between 500 and 650°C, whereas TiO2 deposition is surface reaction limited between 500 and 600 °C, and diffusion limited above 600 °C. At a low pressure of 8 mTorr, ECR oxygen plasma was found to help decompose Ti(i-OC3H7)4. In ECR-CVD mode, the deposition temperature could be lowered to 400 °C. TEM and SEM analyses showed that SrTiO3 thin films have a columnar structure. The size of the grains depends on film thickness, and their shape on film composition (Sr/Ti ). Films prepared by thermal-CVD had a lateral step coverage of 50 %. 40 nm SrTiO3 thin films (Sr/Ti = 1.0) prepared by thermal-CVD on Pt/TaOx/Si and annealed for 2 hours in O2 had a maximum dielectric constant of 139 (Cs = 31 fF/μm2 and teq = 1.1 nm) and a leakage current density of 6x10−8 A/cm2 at 1.0 V.
Oxygen Tracer Diffusion in Sol-Gel Derived Pb(Zr,Ti)O3 thin Films
Authors: Vajo John J. , Momoda L.A. , Wong S.B. , Kamath G.S.
Published: March 2011

We have studied oxygen diffusion in thin films of Pb(Zr,Ti)O3 on Pt/Ti/SiO2/Si <100> multilayer substrates using 18O as a tracer. The PZT films were synthesized using the sol-gel technique and crystallized in air at 650° C for 30 minutes. Diffusion experiments were conducted in one atmosphere of 18O2 at tmipertures between 400-600°C, the extent of exchange was monitored using secondary ion mass spectromentry. Exchange profiles were modeled using solutions of the diffusion equation with boundary conditions for a layer with finite thickness. Significant exchange (>60%) of 16O by 18O was measured after treatment under conditions similar to those used for crystallization. At low levels of exchange, oxygen diffusion does not follow a simple Fickian profile and differences exist between nominally identical films. These results suggest that oxygen exchange is sensitive to the film's microstructure.
The Effect of Composition Dependent Lattice Strain on the Chemical Potential of Tellurium in Pb1−xSnxSe1−yTey Quaternary Alloys
Authors: Mccann Patrick J.
Published: March 2011

IV-VI semiconductor Pb1−xsSnxsSe1−ysTeys quaternary alloys were grown on (111) BaF2 by liquid phase epitaxy (LPE). X-ray diffraction analysis shows that liquid (Pb1−x1Snx1)0.99(Se1−y1Tey1)0.01 solutions produce alloys lattice-matched with the substrate wheny1 = 60%, 58%, and 57%, and x1 = 20%, 40%, and 60%, respectively. These data suggest that the chemical potential of tellurium in the Pb1−xsSnxsSe1−ysTeys solid solution decreases as tin and tellurium concentrations increase. It is argued that this reduction is due to decreasing strain energy driven segregation of tellurium from the solid to the liquid as the tin concentration increases.
Self-Accommodation Mechanisms for Orthorhombic Martensite Formation in Sputtered Thin Films of Thermoelastic Ti(Nicu)
Authors: Chang L. , Grummon D. S.
Published: March 2011

Direct observation of the self-accommodation morphology for orthorhombic martensite in Ti51.0Ni44.4Cu4.6 thin films has been accomplished by transmission microscopy of fine grained (<2μm) material prepared by triode magnetron sputtering. The films were observed to undergo, on cooling, two separate thermoelastic transformations in which the B2 austenite phase first transformed to an orthorhombic martensite with a =.291 nm, b =.425 nm and c =.450 nm followed by transformation to the monoclinic phase at lower temperature. The R-phase transformation was suppressed. Single grains contained as many as eight crystallographic variants of the orthorhombic phase, the majority of which were shaped as parallelograms bounded by {111}Ortho twin planes. The local self-accommodation mechanism produced combinations in which three adjacent variants shared a common {111}B2 pole. Although the majority of B19 variant domains accommodated themselves through {111}Ortho type twinning, a second accommodation mechanism, involving two sets of band-like martensite variants, bounded by {011}ortho twin planes, was also observed. Simultaneous occurrence of the {111}ortho and {011}ortho twinning modes, wihtin a single austenite grain, was not observed.
Strain Relief by Ion Beam Mixing. Molecular Dynamics Simulations Applied to Metallic Hetero-Structures
Authors: Mazzone A.A.
Published: March 2011

This work presents molecular dynamics simulations of low-energy (40-80 eV) ionbeam mixing of thin metallic hetero-structures. The results indicate that the propagation of the cascade may maintain or even restore crystallinity in disordered interfacial regions.
Silicide Formation in Ti-Si and Co-Si REACTIONS
Authors: Clevengert L.L. , Hong Q.Q. , Mann R. , Harpert J.M.E. , Barmake K. , Cabral C. , Nobili C. , Ottaviani G.
Published: March 2011

Titanium silicide and cobalt silicide crystallization and formation reactions are important for the processing of CMOS circuits. We demonstrate that kinetic analysis of these reactions under both high heating rates and isothermal heating conditions allows for the determination of transformation mechanisms. For Ti/Si reactions, we show that the C49 to C54-TiSi2 transformation can not be bypassed using heating rates up to 3000°C/min. For the crystallization of CoSi2 from amorphous Co-Si thin films without ion irradiation, the crystallization kinetics are characterized by three dimensional growth from quickly consumed nucleation sites. With high dose silicon ion implantation of the as-deposited films, the crystallization mechanism changes to homogeneous nucleation and two dimensional growth.
Prediction of Silicide Formation Sequence from the Principle of the Largest Free Energy Degradation Rate
Authors: Zhang Lin , Ivey Douglas G.
Published: March 2011

Recently, a generalized kinetic model for silicide formation has been developed and a principle of the largest free energy degradation rate (largest FEDR) has been proposed. Free energy change rate as a function of diffusion flux has been derived from the kinetic model so that the principle can be justified not only for first phase formation but also for the subsequent processes. Silicide formation sequence predictions, from the model and the FEDR principle, for 15 metal-Si systems have shown very good agreement with the experimental results reported in the literature. In this paper, a brief introduction to the model and the principle is given, followed by examples of the predictions for several metal-Si systems and comparison with experimental results.
Metastable Phase Formation by Interdiffusion
Authors: Johnson W.W.
Published: March 2011

The formation and growth of an amorphous phase or other metastable phases during interdiffusion reactions in metals has been the subject of much study during the past decade [1-4]. The thermodynamic and kinetic factors which control phase selection and growth during the evolution of a binary diffusion couple are of particular interest. Amorphous phase formation in binary A/B diffusion couples has been shown to be favored in systems satisfying several themodynamic and kinetic criteria. First, the free energy of formation of the amorphous phase from the reactants must be negative. This provides the thermodynamic driving force to form the amorphous phase. In general, this condition is best satisfied in cases where the crystalline metals A and B have a negative heat of mixing in the amorphous phase [1,2,4]. On the other hand, the formation of simple crystalline solid solutions of the parent metals should be relatively unfavorable. Thus amorphous phase formation occurs generally in systems for which crystalline terminal solid solutions are restricted. In such binary systems, it is generally true that other crystalline intermetallic phases exist which have lower free energies than the amorphous phase and thus a larger thermodynamic driving force for growth during interdiffusion. As such, additional kinetic constraints must be present which suppress the nucleation and/or growth of the competing crystalline intermetallic phases [2,4].
Examination of Gallium Arsenide Mocvd Reaction Mechanisms
Authors: Windeler Robert S. , Hicks Robert F.
Published: March 2011

A mathematical model has been developed of the reactor used by Larsen et al. [1] to study the kinetics of gallium arsenide MOCVD.- Two different surface reactions were considered as the rate-limiting step in film growth below 500°C: (1) the desorption of methyl radicals from adsorbed trimethylgallium, and (2) the reaction of CH3 and H groups from adsorbed trimethylgallium and arsine to make methane. The latter step is consistent with the experimental results. It explains the rapid acceleration of the precursor decomposition rates when they are fed together to the reactor. It also explains why methane is the only hydrocarbon generated from trimethylgallium and arsine decomposition in deuterium at V/Ill ratios greater than 1.0.
Growth Mechanisms of YBa2Cu3O7-δ Thin Films Post Annealed at a Low Oxygen Partial Pressure
Authors: Hou S. Y. , Werder D. J. , Phillips Julia M. , Marshall J. H.
Published: March 2011

The growth mechanism of YBa2Cu3O 7-= thin films grown by the BaF2 post annealing process at low oxygen partial pressure have been studied by transmission electron microscopy. Under the annealing conditions of po2 = 4 Torr and 700°C, BaCuO2 and Y2 Cu2O5 precipitates develop from stoichiometric film precursors of YBCO during annealing. A growth model is proposed based on the observations. In addition, early stage nucleation and growth of both c- and a-axis oriented grains at the substrate interface were observed in quench annealed cross-sectional samples. 90° [100] symmetrical boundaries form between the a- and c-axis oriented grains. The possible effects of these boundaries are discussed.
Effects of Phosphorus Exposure on Arsenic-Stabilized GaAs 2×4 Surface
Authors: Bensaoula A. H. , Freundlich A. , Bensaoula A. , Rossignol V.
Published: March 2011

Phosphorus exposed GaAs (100) surfaces during a Chemical Beam Epitaxy growth process are studied using in-situ Reflection High Energy Electron Diffraction and ex-situ High Resolution X-ray Diffraction. It is shown that the phosphorus exposure of a GaAs (100) surface in the 500 – 580 °C temperature range results in the formation of one GaP monolayer.
Temperature Dependent Quasi-Periodic Facetting of AlAs Grown by MBE on (100) GaAs Substrates
Authors: Mirin Richard , Krishnamurthy Mohan , Ibbetson James , Gossard Arthur , English John , Petroff Pierre
Published: March 2011

High temperature (≥ 650°C) MBE growth of AlAs and AlAs/GaAs superlattices on (100) GaAs is shown to lead to quasi-periodic facetting. We demonstrate that the facetting is only due to the AlAs layers, and growth of GaAs on top of the facets replanarizes the surface. We show that the roughness between the AlAs and GaAs layers increases with increasing number of periods in the superlattice. The roughness increases to form distinct facets, which rapidly grow at the expense of the (100) surface. Within a few periods of the initial facet formation, the (100) surface has disappeared and only the facet planes are visible in cross-sectional transmission electron micrographs. At this point, the reflection high-energy electron diffraction pattern is spotty, and the specular spot is a distinct chevron. We also show that the facetting becomes more pronounced as the substrate temperature is increased from 620°C to 710°C. Atomic force micrographs show that the valleys enclosed by the facets can be several microns long, but they may also be only several nanometers long, depending on the growth conditions.
Epitaxial Growth of Cu Thin Films on (111)Si at Room Temperature
Authors: Liu C. S. , Chen L. J.
Published: March 2011

Epitaxial growth of Cu thin films on atomically cleaned (111)Si has been studied by transmission electron microscopy (TEM), x-ray diffractometry (XRD) and Auger electron spectroscopy (AES). An interface compound, CuSix with x= 11.2 to 14 at.%, was observed to be present at the Cu/Si interface. Interfacial dislocations at the silicide/Si interface were identified to be of edge type with 1/2<110> Burgers vectors. η“-Cu3Si was found to form in samples annealed at 200 °C for 1 h. Solid phase epitaxial growth of silicon on (111)Si was observed to occur at a temperature as low as 200 °C. Polycrystalline η”-Cu3Si is the only phase present in samples annealed at 200–800 °C. In samples annealed at or higher than 850 °c, a mixture of η′-Cu3Si and η“-Cu3Si were found to be present.
From Adatom Migration to Chemical Kinetics: Models for MBE, Mombe and MOCVD
Authors: Vvedensky D. D. , Shitarat T. , Smilauer P. , Kaneko T. , Zangwill A.
Published: March 2011

The application of Monte Carlo simulations to various epitaxial growth methods is examined from the standpoint of incorporating only those kinetics processes that are required to explain experimental data. A basic model for molecular-beam epitaxy (MBE) is first introduced and some of the features that make it suitable for describing atomic-scale processes are pointed out. Extensions of this model for cases where the atomic constituents of the growing surface are delivered in the form of heteroatomic molecules are then considered. The experimental scenarios that is discussed is the homoepitaxy of GaAs(001) using metalorganic molecular-beam epitaxy (MOMBE) with triethylgallium (TEG) and precursors and using MOCVD with trimethylgallium (TMG). For MOMBE, the comparisons between simulations and experiments are based on reflection high-energy electron diffraction intensities, by analogy with comparisons made for MBE, while for metalorganic chemical vapor deposition (MOCVD) the simulations are compared to in situ glancingincidence x-ray scattering measurements. In both of these cases, the inclusion of a second mobile species to represent the precursor together with various rules for the decomposition of this molecule (in terms of rates and local environments) with be shown to provide a useful starting point for explaining the general trends in the experimental data and for further refinements of the model.
Crystallographic Analysis of (110)CeO2/(100)Si Using RBS/Channeling Technique
Authors: Satoh Masataka , Yamamoto Yasuhiro , Nakajima Shigeyuki , Sakurai Yoshinobu , Inoue Tomoyasu , Ohsuna Tetsu
Published: March 2011

Epitaxially grown CeO2 layers on (100)Si substrates are studied using the RBS/channeling technique. The crystallographic correlation between the overgrown layers and off-oriented Si substrates is precisely analyzed by means of constructing stereographic projections obtained from the planar channeling dips. From the stereographic projections for the CeO2 layer on the 4° off-oriented Si substrate, it is clearly seen not only that the epitaxial (110)CeO2 layer is single crystal with the direction defined as [001]CeO2 ║ [011]Si, but also that the crystalline quality of (110)CeO2 on (100)Si can be improved by use of the off-oriented substrate. The inclined epitaxial direction is also detected as the depth information.
Dislocations Nucleating Growth in Liquid Phase Epitaxy of Gallium Arsenide
Authors: Möhling Werner , Weishart H. , Bauser E.
Published: March 2011

Dislocations in GaAs are analysed by X-ray topography in order to relate their nature to their efficiency in generating growth steps. The analysis is mainly based on comparing double crystal back reflection images of the defects to calculated misorientations of the crystal surface which are caused at the outcrop. All types of dislocations are equally effective provided their Burgers vector has a component normal to the growth interface. Concentric growth step patterns, which develop in varying numbers on different samples are not caused by substrate dislocations.
Evolving Surface Cusps During Strained Layer Epitaxy
Authors: Jesson D. E. , Pennycook S. J. , Baribeau J.-M. , Houghton D. C.
Published: March 2011

We have combined Z-contrast imaging and Ge marker layer experiments to study the evolving surface morphology of SixGel-x alloys grown by molecular beam epitaxy (MBE). Surface cusps are seen to arise as the intersection lines between coherent islands. The potential implications of stress concentrations associated with cusps are considered with a view to strain relaxation in the film via dislocation nucleation.
Effects of Minimizing the Driving Force for Epitaxy in the Ge/Si(001) System
Authors: Hansson P. O. , Bauser E. , Albrecht M. , Strunk H. P.
Published: March 2011

A new technique for Ge/Si heteroepitaxy from the solution, referred to as interfacial energy epitaxy, produces Ge layers with atomically abrupt interfaces to Si and permits monolayer-controlled growth at temperatures up to 937°C. The initial driving force for epitaxy comes from interfacial energy differences between Ge, Si, and the solvent or growth mediator, whose surface free energy has to be smaller than that of Ge. A superheating of the growth solution partly out-balances this driving force, which allows us to minimize the total driving force for epitaxy. Two-dimensional growth results. Subsequent faceting and pseudomorphic island growth manifest additional driving forces for epitaxy, which may be due to interfacial- and strain energy gain.
Strain-Field Induced Crosshatch Formation During Molecular Beam Epitaxy of InGaAs/GaAs Films
Authors: Zhou X. C. , Jiang J. , Du A. Y. , Zhao J. W. , Mu S. M. , Peng L.-M. , Zhong Z. T.
Published: March 2011

Using reflection electron microscopy (REM), transmission electron microscopy (TEM), and Nomarski optical microscopy we obtained direct evidence that local surface strain-fields, originated from misfit dislocations, are responsible for the formation of morphological crosshatches during molecular beam epitaxy of lattice mismatched InGaAs/GaAs layers. A mechanism is proposed to correlate the formation of the crosshatched patterns with the variation of the growth rate across the epitaxial surface under the perturbation of network shaped strain-fields in the surface.
Molecular Dynamics Simulations of Diamond and Carbon Clusters
Authors: Pailthorpe Bernard A.
Published: March 2011

The synthesis of amorphous diamond thin films has been studied previously by classical molecular dynamics computer simulations utilising Stillinger Weber potentials, reparameterised to describe bonding in carbon. The simulations provided insight into the surface processes occuring during thin film growth and showed the role of stress and an energy window in promoting amorphous diamond formation from carbon ion beams. However, more realistic simulations require a full treatment of quantum effects to describe adequately chemical bonding and electronic properties. Local Density Functional theories and the Car-Parrinello molecular dynamics algorithm have proved to be successful and offer a route to first-principles materials design. We are using these techniques to investigate bonding and structure in small carbon clusters and to study doping of diamond required to fabricate electronic devices. Results are presented for a novel, three dimensional, neutral carbon-11 cluster which was studied by ab initio molecular dynamics simulations confirming that, while the 3D structure is stable, the ring is the lower energy structure. However, the 3D structure deforms rapidly to a more open structure of the same topology which is dynamically stable during simulated annealing up to 2000K. Higher quality calculations indicate that new, lower symmetry bonding arrangements form also. Attempts to enclose lithium or boron atoms within the Cl 1 cage caused heating and ultimate rupture into smaller fragments.
Helium Ion Beam Induced Arsenic Atom Displacement Studied by Medium-Energy Ion Spectroscopy
Authors: Yokoyama Shin , Radzimski Zbigniew J. , Ishibashi Kensaku , Watanabe Takeshi , Hirose Masataka
Published: March 2011

An arsenic atom displacement in As+ ion implanted Si induced by He+ ion beam irradiation has been studied by medium-energy (175keV) ion spectroscopy (MEIS). The He+ energy and dose dependences of the displaced arsenic atoms have been examined in the range of 30-175keV and ≤6×10-4C/cm2, respectively. The amount of the displaced arsenic atoms are found to be proportional to the dose and inversely proportional to the nuclear stopping power in the low-dose region, while it saturates at high-dose region. The dose-proportional region is composed of two different proportional coefficient segments.
Nanosized Thallium Inclusions in Aluminium
Authors: Johnson E. , Johansen A. , Bourdelle K.K. , Andersen H.H. , Sarholt-Kristensen L.
Published: March 2011

Ion implantation of pure aluminium with thallium induces formation of nanosized crystalline thallium inclusions with either fee or bee structure. The size of the inclusions depends on the implantation conditions and subsequent annealing treatments. Inclusions less than 10-15 nm in size are generally fee while larger inclusions are bee. The fee inclusions are aligned topotactically with the aluminium matrix with a cube/cube orientation relationship, and they have a truncated octahedral shape bounded by {111} and {001} planes. The lattice parameter of the fee thallium inclusions is 0.484 nm ± 0.002 nm, which is slightly but significantly larger than for the high pressure fee thallium phase known to be stable above 3.8 GPa. The lattice parameter of the bec inclusions is close to the equilibrium value of 0.387 nm and the orientation relationship is given by the Kurdjumov-Sachs rule (011)bcc ║ (111)fcc and [111]bcc ║ [101]fcc The bec inclusions,, representing the high temperature equilibrium phase but existing in metastable equilibrium at lower temperatures, have curved and less well-defined facets. Inclusions with hep structure, the stable phase at room temperature, have not been observed.
Flux Dependence of Amorphous Layer Formation and Damage Annealing in Room Temperature Implantation of Boron into Silicon
Authors: Simonton Robert , Shi Jinghong , Boden Ted , Maillot Philippe , Larson Larry
Published: March 2011

We implanted <100> silicon 200mm wafers with 20keV 11B+ to a fluence of 5×1015 atoms/ cm2 using beam currents from 1-7mA, which produced flux of about 50-350µA/cm2. The implant temperature of all wafers rose no more than five degrees above room temperature, regardless of flux. Cross sectional TEM images (as-implanted) of the highest flux samples revealed a continuous amorphous layer from the implanted surface to a depth of about 530Å. The high flux and <30°C implantation temperature allowed amorphous layer formation even with this moderate boron fluence, as was suggested by Jones, et.al.1. We observed a strong dependence of as-implanted damage on boron flux, as previously reported by Eisen and Welch2. After 900°C, 20 sec RTA, the highest flux samples had 50% lower sheet resistance than the lowest flux samples, due to better activation, as observed in SRP. When a 1050°C, 15 sec RTA was employed, this sheet resistance and activation dependence on flux disappeared. Cross sectional TEM images revealed that the size and number of the Type II end of range defects , which were centered near the amorphous and crystalline as-implanted interface, in the highest flux samples were smaller than the Type 1 dislocation loops centered about the peak disorder in the lowest flux samples after RTA. SIMS and SRP profiles indicated that transient enhanced diffusion during the 900°C, 20 sec RTA may have been reduced in the highest flux samples. Based on these observations and on previous reports, we conclude that sufficiently high flux during room temperature boron implantation will produce a continuous amorphous layer with doses that are appropriate for p-type source/drain formation. The amorphous layer will produce improved activation and damage annealing behavior in subsequent RTA, particularly as the RTA temperature is reduced.
Defect Induced Amortization in Silicon: A Tight Binding Molecular Dynamics Simulation
Authors: Maric D. , Colombo L.
Published: March 2011

We present an investigation on the amorphization process of crystalline silicon induced by ion beam bombardment by simulating the insertion of self-interstitials at different temperatures. The simulation is carried out by tight-binding molecular dynamics which allows for a detailed characterization of the chemical bonding and electronic properties of the irradiated samples. The irradiation process consists of two steps: (i) insertion of defects at a constant rate; (ii) annealing of the sample and observation of its structural properties. Thanks to the large size of the simulation cell (up to 276 atoms) we can characterize the amorphous network both on the short-range and medium-range length scale. Electronic properties are investigated as well and their evolution is monitored during the insertion process. Finally, we present a thorough comparison of the structural properties of the irradiated sample with amorphous silicon as obtained by rapid quench from the melt.
Amorphization and Dynamic Recovery of A2BO4 Structure Types During 1.5 MeV Krypton Ion-Beam Irradiation
Authors: Wang L.M. , Gong W.L. , Ewing R.C.
Published: March 2011

The temperature dependence of the critical amorphization dose, Dc of four A2BO4 compositions, forsterite (Mg2SiO4), fayalite (Fe2SiO4), synthetic Mg2GeO4, and phenakite (Be2SiO4) was investigated by in situ TEM during 1.5 MeV Kr+ ion beam irradiation at temperatures between 15 to 700 K. For the Mg- and Fe-compositions, the A-site is in octahedral coordination, and the structure is a derivative hcp (Pbnm); for the Be-composition, the A- and B-sites are in tetrahedral coordination, forming corner-sharing hexagonal rings (R3). Although the Dc's were quite close at 15 K for all the four compositions (0.2–0.5 dpa), Dc increased with increasing irradiation temperature at different rates. The Dc-temperature curve is the result of competition between amorphization and dynamic recovery processes. The Dc rate of increase (highest to lowest) is: Be2SiO4, Mg2SiO4, Mg2GeO4, Fe2SiO4. At room temperature, Be2SiO4 amorphized at 1.55 dpa; Fe2SiO4, at only 0.22 dpa. Based on the Dc-temperature curves, the activation energy, Ea, of the dynamic recovery process and the critical temperature, Tc, above which complete amorphization does not occur are: 0.029, 0.047, 0.055 and 0.079 eV and 390, 550, 650 and 995 K for Be2SiO4, Mg2SiO4, Mg2GeO4 and Fe2SiO4, respectively. These results are explained in terms of the materials properties (e.g., bonding and thermodynamic stability) and cascade size which is a function of the density of the phases. Finally, we note the importance of increased amorphization cross-section, as a function of temperature (e.g., the low rate of increase of Dc with temperature for Fe2SiO4).
A Cubic Phase Formed in Immiscible Fe/Ag(Cu) System S by Ion Mixing
Authors: Liu B.X. , Pan F. , Tao K.
Published: March 2011

FexAg1-x (x=0.20-0.65) and Fey Cu1-y (y=0.50-0.75) nano-multilayers were prepared by alternative deposition of pure constituent metals. Ion mixing of the multilayers by 200 keV xenon ions at 77K resulted in the formation of a similar metastable phase with a big lattice of cubic structure, when the ion dose exceeded 1×1016 and 1×1015 Xe+/cm2 for Fe/Ag and Fe/Cu systems, respectively. The fraction of the new phase emerged in the alloy films increased with increasing ion dose in both cases.
Piezoresistivity in Ion Implanted Polymer Films
Authors: Wang Y.Q. , Robey D.S. , Giedd R.E. , Moss M.G.
Published: March 2011

Piezorcsistive properties have important sensor applications. In this study we find that several ion implanted polymers exhibit piezorcsistive properties. Piezoresistive gauge factors of these films are found to be significantly greater than those of metals, however smaller than those of semiconductors. Potential advantages of using the piezorcsistive properties of these films are also discussed.
Ion Beam Synthesis of Luminescent SI and GE Nanocrystals in a Silicon Dioxide Matrix
Authors: Atwater H.A. , Shcheglov K.V. , Wong S.S. , Vahala K.J. , Flagan R.C. , Brongersma M.L. , Polman A.
Published: March 2011

Ion beam synthesis of Si and Ge nanocrystals in an SiO2 matrix is performed by precipitation from supersaturated solid solutions created by ion implantation. Films of SiO2 on (100) Si substrates are implanted with Si and Ge at doses 1 × 1016/cm2 - 5 × 1016/cm2. Implanted samples are subsequently annealed to induce precipitation of Si and Ge nanocrystals. Raman spectroscopy and high-resolution transmission electron microscopy indicate a correlation between visible room-temperature photoluminescence and the formation of diamond cubic nanocrystals approximately 2–5 nm in diameter in annealed samples. As-implanted but unannealed samples do not exhibit luminescence. Rutherford backscattering spectra indicate a steepening of implanted Ge profiles upon annealing. Photoluminescence spectra are correlated with annealing temperatures, and compared with theoretical predictions for various possible luminescence mechanisms, such as radiative recombination of quantum-confined excitons, as well as possible localized state luminescence related to structural defects in SiO2. Potential optoelectronic device applications are also discussed.
Accumulation of Implantation Damage in MEV Implanted Diamond Crystals
Authors: Hunn John D. , Withrow S.P. , Clausing R.E. , Heatherly L. , Bentley J. , Hembree D.M. , Parikh N.R.
Published: March 2011

Single crystal, type IIa natural diamond substrates have been implanted with 4 MeV carbon ions to doses ranging from 0.5–130×1016 cm-2. The accumulation of implantation damage is studied by Raman and RBS/channeling. Similar effects are observed for crystals of [100], [110], and [111] orientation but with different rates of damage accumulation. With increasing implantation damage, the triply degenerate Raman mode at 1332 cm-1 broadens and shifts down to around 1300 cm-1. This corresponds to a peak in the one-phonon density of states as predicted for Raman from an amorphous sp3 network. There is no evidence for the existence of sp2 carbon in the implanted area. Additional non-graphite Raman peaks appear at 1451, 1494, and 1635 cm-1. At the higher doses, the 1332 cm-1 Raman mode is no longer observed; however, RBS/channeling still shows the surface region to be crystalline and it is possible to grow high quality homoepitaxial diamond films on these substrates.
Characterization of Thermally Annealed Sb Implanted Fused Silica
Authors: Morgan S.H. , Pan Z. , Henderson D.O. , Park S.Y. , Weeks R.A. , Magruder R.H. , Zuhr R.A.
Published: March 2011

The local environment of the polarizable ion in heavy metal oxide glasses is postulated to strongly influence the nonlinear response of these materials. We have previously observed that post-implantation thermal annealing changes the chemical properties of the implanted layer in a different fashion in Pb- and Bi- implanted SiO2. In this paper we report the optical behavior of Sb-implanted SiO2 as a function of annealing temperature and atmosphere. High purity fused silica substrates were implanted at room temperature to a dose of 6 × 1016 ions/cm2, and subsequently annealed at temperatures from 500 to 1000 C in argon and oxygen atmospheres. RBS, optical absorption (1.8 to 6.2 eV), infrared reflectance (450 to 5000 cm-1), and nonlinear index of refraction were measured before and after annealing. The results of these measurements indicate that annealing treatment significantly affects the local environment of the implanted Sb ions, and consequently the optical response.
Colloidal Au Nanoclusters Formed in Fused Silica by MeV Ion Implantation and Annealing
Authors: White C. W. , Zhou D. S. , Budai J. D. , Zuhr R. A. , Magruder R. H. , Osborne D. H.
Published: March 2011

MeV implantation of Au has been used to create a high density of Au nanoclusters in the near surface of fused silica. Measurements of the nanocluster size and size distribution under various implantation/annealing conditions are presented and correlated with measurements of optical absorption arising from surface plasmon resonance absorption by the Au nanoclusters in fused silica. Preliminary measurements of the nonlinear refractive index are included.
Application of Coatings for Electromagnetic Gun Technology
Authors: Otooni M. A. , Graf A. , Colombo G. , Conrad J. , Sridharan K. , Shamim M. M. , Fetherston R. P. , Chen A.
Published: March 2011

Copper and aluminum are extensively used in various parts of the Electromagnetic (EM) Gun systems. Copper is used in the design of the railgun because it has favorable electrical and thermal properties. Aluminum is used for armature and sabot fabrication because of it is light weight and has favorable thermal properties. Extensive degradation of the copper rail and aluminum armature occurs owing to the severe heating and thermomechanical deformation of these components during operation of the EM gun. In this research effort, several modification techniques were used to protect the rail and armature materials from these degradation processes. These include application of Plasma Source Ion Implantation (PSII) and Ion Beam Enhanced Deposition (IBED) . By using these techniques, the copper rails and aluminum armatures were coated with TiN and TaN. Several characterization techniques were used to assess the chemical,mechanical and other properties of these modified surfaces. Optical Microscopy, Scanning and Transmission Electron Microscopy, and Scanning Auger Spectroscopy techniques were also used. Microhardness measurements have also been performed. From the results of this preliminary investigation, it has been concluded that the surface properties of the coated rail and armature materials have been improved and the extent of wear and spark erosion from these surfaces has been reduced.
Improvement of Strength and Reliability of Structural Ceramic through Ion Implantations
Authors: Bhattacharya Rabi S. , Rai A.K.
Published: March 2011

The feasibility of strength and reliability improvements of Si3N4 through ion implantations has been studied. The approach has been to implant elements that may chemically combine with themselves to form precipitates after appropriate annealing. These precipitates can improve the strength and reliability of ceramics through the introduction of a compressive stress in the implanted surface layer and/or by modifying the fracture originating machining flaws. Sequential implantations of ion pairs of Ti+ and C+, and Si+ and C+ were performed at energies in the range 46 to 175 keV and at doses of 1×1017 cm-2 for each ion species. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM) techniques were used to analyze the implanted layer. Strength and reliability were determined from four-point flexure strength measurements. Precipitates of TiN and C were found to form in Ti++C+ and Si++C+ implanted Si3N4 surfaces, respectively. Si++C+ implantation resulted in improvements of both strength and reliability of Si3N4, while Ti++C+ implantations had no effect.
Structural Characters and Tribological Properties of Diamondlike Carbon Films
Authors: He Xiao-Ming , Li Wen-Zhi , Li Heng-De
Published: March 2011

Diamond-like carbon films have been prepared by using dual ion beam sputtering deposition under CH++Ne+ bombardment with energies 50–800 eV. The obtained films possess a smooth surface and an amorphous structure containing some sp3 bondings. DLC films bombarded by low energy CH++Ne+ exhibit the relatively high binding energy and electrical resistivity which are approximate to those of diamond. It is believed that a Mo interlayer between AISI 52100 steel substrates and DLC films brings the films good adhesion. This offers promises to DLC films on bearing steel to perform a stable wearing in much lower friction coefficient (<0.1) under large wear loads (30–90N). Experimentally, low wear coefficients and high anti wear numbers obtained prove that the DLC films indeed possess excellent wear resistance. In addition, the speed or the momentum of friction motion was revealed to exert some serious effects upon the wear resistance of DLC films when the wearing was carried out under very high wear load (> 30 N).
Electric Field Induced De-channeling in LiNbO3
Authors: Zimmerman R. L. , Ila D. , Kukhtarev N. , Williams E. K.
Published: March 2011

An electric field has been imposed on single crystals of pure and doped LiNbO3 during bombardment with 1.03 MeV protons and 2.1 MeV alpha particles. Simultaneous (p,p), (p,α) and (p,p'γ) channeling between the crystal planes showed that the channeling is less pronounced when an electric field of 106 volts/m is imposed perpendicular to the incident ion beam direction and to the channeling planes in the crystal. The results obtained are discussed and compared to the effects due to the fringe field outside the crystal, differential cation-anion movement, movement of interplanar impurities, the piezoelectric strain and movement or creation of crystal defects on ion channeling.
Simox Material Development for Sub-0.25µm Cmos Technology
Authors: Sadana D.K. , Hovel H.J. , Frecouf J.L. , Chu S.F. , Watson T.J.
Published: March 2011

Advantages of SOI materials for CMOS technology arc discussed. The lending SOI materials for CMOS applications appear to be SIMOX and BSOl presently. Progress made in two types of SIMOX, namely, standard and thin BOX. is presented. Recent results from 200mm SIMOX are included. Finally, various defects in annealed SIMOX are discussed. An effort has been made to present data which is typical of commercial SIMOX.
Defect Pair Formation by Implantation-Induced Stresses in High-Dose Oxygen Implanted Silicon-on-Insulator Material
Authors: Lee J.D. , Park J.C. , Venables D. , Krause S.J. , Roitman P.
Published: March 2011

Defect microstructure and the near-surface strain of high-dose oxygen implanted silicon-on-insulator material (SIMOX) were investigated as a function of dose, implant temperature, and annealing temperature by transmission electron microscopy and high resolution x-ray diffraction. Dislocation half loops (DHLs) begin to form by stress assisted climb at a critical stress level due to implantation-induced damage. DHLs evolve into through-thickness defect (TTD) pairs by expansion during annealing. Both DHL and TTD-pair density increase with higher implant dose and lower implant temperature. Possible methods for defect density reduction are suggested based on the results of this study.
Characterization of GeSi Layer Formed by High Dose Ge Implantation into Si
Authors: Cheung W.Y. , Wong S.P. , Wilson I.H. , Zhang T.H.
Published: March 2011

High dose Ge implantation into p-type <100> Si wafers at 150 keV has been performed at doses of 3.6×1016, 6.7×1016 and 9.0×1016 cm-2. The Ge distribution and the crystal quality of the implanted layer before and after annealing at various temperatures have been studied by RBS and channelling experiments. It is found that for the medium and high dose samples before annealing, more than 90% of the Ge atoms are in interstitial sites and after annealing at 1000°C, more than 50% of the Ge atoms have become substitutional. The situation is better for the low dose sample where less than 70% of the Ge atoms are in interstitial sites before annealing and about 80% of them become substitutional after annealing at 1000°C. The ESR spectra of these samples are of lorentzian shape with a g-value of about 2.007 and a spin density of about 6×1016 cm-3. The ESR signals of these samples have been inferred to be mainly due to Si-dangling bonds in the GeSi alloy layer and can be eliminated by annealing at 1000°C for 10 minutes. Electrical characterization of the GeSi layer by spreading resistance profiling technique shows that the implantation damage has been extended deep into the substrate before annealing. After annealing at 1000°C, these defects are removed but the spreading resistance of the surface GeSi layer is found to remain higher than that of the substrate.
Growth Rate of Solder Intermetallics
Authors: Demaree J. D.
Published: March 2011

The formation of intermetallic layers between copper wires and lead-tin solders is indicative of the strong metallurgical bond required for a durable solder joint Previous studies have shown that these interracial compounds grow at significant rates (up to 1 µm/day at 100°C), and differences in thermal expansion and hardness between the metals and the intermetallics can lead to the mechanical failure of the solder joint during service. Most previous measurements of the compound formation rate have used elevated temperatures to facilitate the direct observation of the intermetallic thickness by optical microscopy, SEM, or TEM. In this study, Rutherford backscattering spectrometry (RBS) has been used to study the intermetallic growth rate using sputter-deposited thin films of Cu and PbSn. The extraordinary depth sensitivity of RBS (~10 nm) allows these measurements to be made in relatively short times, without the need for heat treatment to accelerate the reaction. Measurements have indicated that at least 23 nm of Cu6Sn5 and 30 nm of Cu3Sn form between Cu and PbSn solder in less than one hour. Faster deposition methods are being investigated to further characterize this rapid reaction. Iron has been proposed as a diffusion barrier material to inhibit intermetallic growth in solder joints. Preliminary measurements of the solder/Fe reaction indicates a much slower rate of growth, with less than 50 nm of total intermetallic forming over 8 hours.
Low Energy Ion Implantation / Deposition as a Film Synthesis and Bonding Tool
Authors: Anders André , Anders Simons , Brown Ian G. , Ivanov Igor C.
Published: March 2011

We describe a novel means for the production of atomically-bonded thin films of a wide range of materials. The technique is a plasma and ion beam method involving synthesis of the desired surface film by plasma deposition and the simultaneous atomic mixing of the film into the substrate by low energy ion implantation from the surrounding plasma. Vacuum-arc-produced metal plasma is used for the metallic component of the film and gases can be added to form compound films. Multiple plasma generators can be used, and films of single metals, alloys, ceramics and multilayers can be formed. By repetitively pulse biasing the substrate during plasma deposition, the growing film is subjected to energetic ion bombardment, and direct and recoil ion implantation is induced. The depositing film is thereby atomically mixed to the substrate as it is formed. The films are atomically smooth, can be anywhere from a few monolayers to microns in thickness, and the interface or mixed transition zone can be tailored. Here we outline the basic plasma physics of the method and describe a number of novel surfaces which have been formed with excellent properties.
Element Profiles of Surface Layers Created by Metal Ion Beam Assisted Deposition
Authors: Duvanov Sergei M. , Kobzev Alexander P. , Tolopa Alexander M.
Published: March 2011

Depth profiles of elements in the surface layers of metals and metallized dielectrics were investigated by Rutherford Backscatteríng Spectrometry (RBS) (for the depth profiling of heavy elements), resonant elastic Backscattering Spectrometry (BS) of 4He+ and 1H+ (for the light elements depth profiling), Elastic Recoil Detection (ERD) of 1H+ (for depth profiling of hydrogen atoms), SIMS and AES techniques. The technological TAMEK source operated in the regime of ion beam assisted deposition (IBAD) of the metal ions (ion implantation at average beam energy ≤ 150 KeV and simultaneous deposition of the same ions at energy 100 eV) in pulse mode. Coatings were deposited on metal and glass samples at temperature of substrates T=100° C. In this report, we discuss the investigation results of samples modified by IBAD in technical vacuum produced by oil diffusion pumping. Phases like TiO, TiC, TiN, TiH are indicated in interface coating-substrate layers. The total thickness of mutually mixed metal-glass layer was found to be 400 nm and it was equal up to 3 µm for metal-metal layers. Cu/Al thin layers on a glass subsrate may be used as mirrors for powerful lasers with large (up to 5 J/cm2) energy contribution.
Epitaxial Planarization Using Ion Beam Assisted Deposition
Authors: Chang Bertha P. , Sonnenberg Neville , McIntyre Paul C. , Cima Michael J. , Sun Jonathan Z. , Yu-Jahnes Lock See
Published: March 2011

CeO2 thin films have been deposited on patterned (100) LaAlO3 substrates using ion beam assisted deposition (IBAD) with ion beam energies between 350 and 500eV. Deposition temperatures were varied between 400°C and 600°C and deposition rates from 0.2Å/s to 1.2Å/s. Both normal and off-normal incidence ion bombardment have been studied. A trend towards planarization is observed when the ion to atom ratio is adjusted to obtain the proper degree of etching. The planarization mechanism for normal incidence bombardment appears to be similar to that previously observed for bias sputtering. X-ray diffraction shows that an initial layer of evaporated epitaxial CeO2 is required for continued epitaxial development during IBAD processing. The extent of planarization via off-normal ion incidence can be related to the direction of the ion beam with respect to the patterned features. X-ray pole figure measurements show that these films possess an in-plane orientation that is directly related to the ion beam parameters.
ECR Plasma Synthesis of Silicon Nitride Films ON GaAs and InSb
Authors: Barbour J. C. , Lovejoy M. L. , Ashby C. I. H. , Howard A. J. , Custer J. S. , Shul R. J.
Published: March 2011

The growth of high-quality dielectric films from Electron Cyclotron Resonance (ECR) plasmas provides for low-temperature surface passivation of compound semiconductors. Silicon nitride (SiNx) films were grown at temperatures from 30°C to 250°C on GaAs substrates. The stress in the films was measured as a function of bias applied during growth (varied from 0 to 200 V), and as a function of sample annealing treatments. Composition profiles of the samples were measured using ion beam analysis. The GaAs photoluminescence (PL) signal after SiNx growth without an applied bias (ion energy = 30 eV) was twice as large as the PL signal from the cleaned GaAs substrate. The PL signal from samples biased at -50 and -100 V indicated that damage degraded the passivation quality, while atomic force microscopy of these samples showed a three fold increase in rms surface roughness relative to unbiased samples. The sample grown with a bias of-200 V showed the largest reduction in film stress but also the smallest PL signal.