bluuebunny/crossref_metadata_2025_split huggingface dataset:
Systematic Preparation Of Polyoxometalate Pillared Layered Double Hydroxides Via Direct Aqueous Reaction
Authors: Wang Jiandang , Tian Ying , Wang Ren-Chain , Colón Jorge L. , Clearfield Abraham 
Published: March 2011

ABSTRACTThe series of layered double hydroxides, MgnAl(OH)2n+2X (n = 2–5, X = NO3− or Cl−) and NinAl(OH) 2n+2X (n = 2–4, X = NO3− or Cl−), were pillared with polyoxometalate ions of the Keggin structure, ranging from [PW12O40]3− to [PV4W8O40]7−, in aqueous solution. Full exchange of the Keggin ions into the layers is achieved as evidenced by X-ray powder diffraction, infrared spectroscopy, elemental analysis and thermogravimetric analysis. Also, partial exchange was observed for Ni5Al(OH)12NO3 The key factor that effects these reactions is the pre-swelling step. Thus, when the layered double hydroxides are thoroughly wet either by preparing wet solids or by soaking the dried products for an extended period, pillaring reactions proceed with great ease. Relations can be extracted between the water content and the separation between the layers, as well as between layer charge density and the charge of the Keggin ion. The pillared layered double hydroxides were found generally to have interlayer distances ranging from 11.0 to 13.5 Å, which is smaller than the numerical sum of the Keggin ion diameter and the ideal thickness of the hydroxide layer. This fact and the low crystallinity are attributed to strong interaction between the basic layered double hydroxides and the acidic Keggin ions. A more crystalline phase with the expected 14.5 Å interlayer spacing was also obtained as a mixture with the lower spaced products.
Preparation of Montmorillonite-p-Aminoazobenzene Intercalation Compounds and Their Photochemical Behavior
Authors: Ogawa Makoto , Fujii Keiko , Kuroda Kazuyuki , Kato Chuzo 
Published: March 2011

ABSTRACTHomoionic-montmorillonite-p-aminoazobenzene intercalation compounds were prepared by novel solid-solid reactions at room temperature. When Na-, Ca- and Ni-montmorillonites were used as host materials, the absorption maxima of p-aminoazobenzene changed considerably upon intercalation, causing the difficulty of studying photochemical behavior of the intercalated dyes. The n-dodecylammonium-montmorillonite-p-aminoazobenzene intercalation compound gave an absorption spectrum similar to that observed for p-aminoazobenzene dissolved in benzene. The intercalated paminoazobenzene in the interlayer space of n-dodecylammoniummontmorillonite exhibited reversible cis-trans photoisomerization by irradiation of UV light.
Raman Microprobe Analysis of Simox Structures Implanted With Screen Oxide
Authors: Perez-Rodriguez A. , Morante J. R. , Martin E. , Jimenez J. , Margail J. , Papon M. A. 
Published: March 2011

ABSTRACTThe analysis of SIMOX structures obtained by doing the implantation with different thicknesses of thermal oxide (screen oxide) has been perfomed by Raman scattering, and the results have been correlated with those previously obtained by TEM. The use of a microRaman system on low angle bevelled sample has allowed to directly observe the different regions in the structures, corroborating the structural differences observed by TEM as a function of the screen oxide thickness. For as implanted structures, strong non homogeneous strain and disorder effects are observed in the top Si layers. After the High Temperature Anneal (HTA) process, crystalline quality of the structures is improved. The analysis of the spectra obtained at different excitation powers points out the dependence of the thermal effects of the spectra on the structural features of the scattering volume, as the dislocation density in the annealed layers. This dependence allows the assesment of the crystalline quality of these structures to be made.
Localized Crystallinity Measurement of Single-Crystal Ge on Insulator by Raman Polarization
Authors: Kato K. , Takai M. 
Published: March 2011

ABSTRACTAgglomeration has occurred during zone-melting to obtain single-crystal germanium layers because of insufficient wettability between germanium and silicon-dioxide. The agglomeration could be suppressed by controlling the capping layer thickness, germanium layer thickness, and the island shape. A rotation of crystal orientation was found in the stripe shape island, which was presumably caused by the stress relieving within an island.
Picosecond Photocarrier Lifetimes in Ion-Irradiated Amorphous and Crystalline Silicon
Authors: Stolk P. A. , Calcagnile L. , Roorda S. , van Linden H. B. , Heuvell Van den , Saris F. W. 
Published: March 2011

ABSTRACTCrystalline silicon (c-Si) and structurally relaxed amorphous silicon (a-Si) were implanted with 1 MeV Si+ at liquid nitrogen temperature. The photocarrier lifetime τ in the implanted samples was determined with sub-picosecond resolution through pump-probe reflectivity measurements. At low damage levels (i.e. <1014 ions/cm2), τ decreases with increasing ion dose in both materials, indicating a build up of trapping and recombination centers. The dominant centers in c-Si appear to be related to simple defects. The generation rate of electrically active defects is found to be the same in relaxed a-Si and c-Si, which suggests that the structural defects formed in a-Si strongly resemble the simple defects in c-Si. For ion doses > 1014 /cm2, τ saturates at a level of 0.8 ps for both materials. Strikingly, the saturation sets in far below the dose needed to amorphize (>1015 /cm2). The defect density in a-Si at saturation is estimated to be ≈1.6 at.%.
Evolution of Buried Oxide “Pipe” Defects Upon Implantation Through Particles in Simox Material
Authors: El-Ghor M. K. , Joyner K. A. , Hosack H. H. 
Published: March 2011

ABSTRACTWe have investigated the effect of the presence of oxide particles on the surface of silicon wafers during high energy, high dose implantation of oxygen into silicon. It was found that for single implants with doses of 1.5 × 1018/cm2 or 1.8 × 1018/cm2, such particles produce a non-continuous buried oxide layer in the as-implanted condition as well as after annealing. Etching results showed that no defects, which formed etchable paths through the buried oxide, were produced for particles with diameters 0.43 um or below for the lower dose and 0.53 um for the higher dose.
The Detailed Variation of Boron and Fluorine Profiles with Tilt and Rotation Angles for BF2+ ION Implantation in (100) Silicon
Authors: Gupta Puneet , Park Changhae , Klein Kevin , Yang Shyh-horng , Morris Steve , Do Vu , Tasch Al , Simonton Robert , Lux Gayle 
Published: March 2011

ABSTRACTOver 250 boron and over 250 fluorine profiles have been obtained from BF2+ implants over a wide range of implant energies, doses, tilt angles, and rotation angles. A detailed study has been conducted on the boron and fluorine profile variations with the tilt and rotation angles over the available range of energies and doses. Channeling through a few low index axial and planar channels in (100) silicon has been found to account for the observed profile variations with implant angle. Tilt and rotation angle combinations which minimize channeling and ensure process uniformity have been deduced.
Sb Implantation in Si1–xGex/Si(100) Structures
Authors: Atzmon Z. , Eizenberg M. , Revesz P. , Mayer J. W. , Schäffler F. 
Published: March 2011

ABSTRACTSolid phase epitaxial regrowth of Sb implanted strained Si1−x Gex alloy layers is reported. Two sets of Si1–xGex alloys with compositions of x=0.08 and x=0.18, MBE grown on (100)Si substrates, were implanted at room temperature with Sb− ions at energies of 200 and 100 keV, respectively, and a dose of 1015cm−2. These alloys were heat-treated in a rapid thermal annealing system at temperatures of 525, 550 and 575°C for durations between 5 and 600 sec. The study of the solid phase epitaxial regrowth was performed by Rutherford backscattering in the channeling mode. The measurements show a significant difference in the regrowth mechanism between the two alloys. For the Si0.92Ge0.00 alloy a fast regrowth process (faster than for Sb implanted Si or Si implanted SiGe layers) occured with an activation energy of 2.92±0.2eV. For the Si0.02Ge0.10 alloy the regrowth took place in two steps: a) a very fast initial process over a short distance, b) a regrowth process of the majority of the amorphous layer.
Diffusion and Phase Formation During Combined Heating and Sputter Etching
Authors: Harper J. M. E. , Hong Q. Z. , Motakef S. , Kelly R. 
Published: March 2011

ABSTRACTSputter etching normally removes material with an overall composition equal to the target composition. At room temperature, this steady-state removal process is usually quickly established by the formation of an altered surface layer which compensates for preferential sputtering, together with an altered subsurface layer which reflects the existence of bombardment-induced Gibbsian segregation (GS). At elevated temperature, ordinary GS, diffusion and the presence of compound phases may strongly affect the development of the steady-state condition. In this paper, we describe two cases in which diffusion and GS become significant processes during sputter etching of a compound material AxB1−x on an underlying substrate of B atoms. In the first case, diffusion is dominated by the substrate species. This case is demonstrated by the sputtering of TiSi2 on (100) Si by 300 eV Ar+. At room temperature, normal sputtering of the TiSi2 layer occurs. At elevated temperature (500–700°C), however, Si diffuses from the substrate to the surface, where it undergoes GS. This allows the development of a steady-state highly selective sputtering of Si atoms, accompanied by movement of the TiSi2 layer into the substrate. In the second case, diffusion is dominated by the non-substrate species. This case is demonstrated by CoSi2, for which the development of steady-state etching occurs in two distinct stages which are strongly temperature-dependent. In this material, Co is the dominant diffusing species, and it is unclear whether or not Si GS occurs. What is clear, however, is that Ar+ bombardment at 500–600°C leads to partial decomposition of the CoSi2 layer and diffusion of Co towards the substrate Si, where new CoSi2 is formed. The combination of sputter etching and elevated temperature is shown to be a controllable environment for compound phase formation at a buried interface.
Silicide Formation in High-Dose Fe-Implanted Silicon
Authors: Tan Z. , Namavar F. , Heald S. M. , Budnick J. I. , Sanchez F. H. 
Published: March 2011

ABSTRACTWe have studied the silicide formation in Fe-implanted Si(100), with 1×1017-1×1018 Fe/cm2, using extended x-ray-absorption fine structure (EXAFS), x-ray diffraction and Rutherford backscattering spectrometry (RBS) methods. In the samples as-implanted at 350 °C, no silicide was observed at doses below 3×1017 Fe/cm2. At 5×1017 Fe/cm2, both α-FeSi2 and (β-FeSi2 form but α-FeSi2 appears to be the majority phase. As the dose increases to 7×1017 and above, ordered FeSi forms, but implantation damage is severe and a large number of Fe atoms are in very disordered environments. In addition to FeSi, Fe5Si3 was also observed in the 1×1018 Fe/cm2 sample. Upon post-implantation annealing at 700 °C or 900 °C, single phase P-FeSi2 was obtained independent of the dosage.
Phase Formation of Platinum Silicides Formed by Ion Implantation
Authors: Kalkhoran Nader M. , Namavar F. , Perry D. , Cortesi E. 
Published: March 2011

ABSTRACTWe have studied the formation of platinum silicide layers by ion implantation and annealing, and have determined the dependence of platinum silicide phase formation on ion implantation conditions and substrate orientation. The results indicate that in most cases, the ion implanted layer consists of PtSi phase. However, depending on the implantation and annealing conditions and substrate orientation, other phases, including Pt2Si, Pt3Si, and Pt12Si5, as well as Si and Pt microcrystals, also form.
Study of Amorphization Process in Silicon Irradiated by Different Ions Using In Situ Stress-Measurement and TEM Techniques
Authors: Yuan Jianzhong , Verner Igor V. , Maksimov Sergei K. , Corbett James W. 
Published: March 2011

ABSTRACTDetailed measurements of the stresses induced by implantation of ions of different types, such as light ions: boron and nitrogen, and heavy ions: argon, krypton and xenon, were carried out in situ on thin silicon films. The measurement were made for keV energy of ions, for a wide range of doses and for different values of the dose rate. Experimental results indicate that the ion-beam-induced transformation in silicon is dose-rate dependent for light ions, as well as for heavy ions. The last conclusion contradicts the classical ideas of amorphization of elemental semiconductors by heavy ions that are based on the concepts of a heterogeneous mechanism of formation of the amorphous state during implantation. Heavy-ion implantation behaves similarly with light-ion implantation at a higher sample temperature. A comparison TEM investigation with stress measurement was made. The results indicate that i) the ion-beam-induced deformation correlates with structural changes and ii) both homogeneous and heterogeneous mechanisms are involved in the structural changes. The results are discussed in terms of non-equilibrium phase transitions in silicon under irradiation.
Erbium-defect interactions in silica films implanted with MeV Er ions
Authors: Polman A. , Jacobson D. C. , Poate J. M. 
Published: March 2011

ABSTRACTThe effect of ion implantation damage on energy transfer processes in Er-doped silica films prepared by MeV ion implantation is studied, using measurements of the luminescence decay of Er3+(4ƒ11) at 1.535 μm. Silica films implanted with Er and annealed at 900°C show a luminescence lifetime of 14.1 ms. Subsequent irradiation with MeV C, Si, or Ge ions at fluences as low as 1011 ions/cm2 decreases the lifetime, which eventually saturates at 6.6–7.8 ms for fluences larger than 1014 ions/cm2. The fluence required to saturate and the lifetime at saturation depend on the ion used. These results are interpreted in terms of non-radiative energy transfer processes caused by irradiation-induced defects in the silica. The ion damage effects are mainly caused by the electronic component of the energy loss along the ion trajectories.
Formation of Au Colloid Particles in Silica Glass by Ion Implantation.
Authors: Fukumi K. , Chayahara A. , Adachi M. , Kadono K. , Sakaguchi T. , Miya M. , Horino Y. , Kitamura N. , Hayakawa J. , Yamashita H. , Fujii K. , Satou M. 
Published: March 2011

ABSTRACTFormation of Au colloid particles and their optical property have been investigated in silica glasses implanted with Au+ ions at an acceleration energy of 1.5MeV and fluence levels of 1016-1017 ions/cm2. The Au colloid particles are formed in the as-implanted glasses. It is inferred that the average radius of Au colloid particles depends on the fluence level, although the fluence level does not affect the distribution of Au atomic concentration. The heat-treatment little affects the Au atomic distribution. The Au colloid particles grow to 4.3nm in average radius during heat treatment. It is revealed that the large nonlinear optical property of the Au+ -ion-implanted silica glass is attributed to the high concentration of the Au colloid particles in the narrow region.
Dynamic Redistribution of Excess Charge During Photoemission in an Electron Bombarded Glass-Ceramic
Authors: Carroll D. L. , Doering D. L. , Blais B. S. 
Published: March 2011

ABSTRACTWe have measured the energy distribution of excess charge trapped by an electron irradiated mica-glass ceramic, Macor™. Photoelectron emission as a function of incident wavelength shows two distinctly different contributions to the measured density of electron trap states. First, there is a broad continuum of binding states which extends well above the Fermi level. This results in spontaneous electron emission which depletes the excess charge in these states rapidly at room temperature and more slowly at 170K. The free decay of charge emission can be described semiclassically. Second, localized trap states appear as peaks on the continuum distribution which occur at 2.7 and 3.1 eV. These correspond to two thermionic emission peaks which occur during heating at 550K and 595K respectively. Photoemission at high intensities using the 458, 488, and 514 nm wavelengths of an argon ion laser and the 632 nm wavelength of a He-Ne laser greatly enhances the depletion of excess charge from the sample. The laser-induced emission intensity is initially high and drops rapidly, followed by a more gradual decrease. The initial intensity measures the population of electrons with binding energies less than the photon energy. The later emission is related to the repopulation of these states by the dynamic redistribution of electrons from deeper states. This behavior may lead to a model for the mechanism of electron redistribution in charged insulating materials.
The Role of Ballistic, Electronic, and Thermal Processes in Electron Irradiation Damage of Maximum Valence Transition Metal Oxide Surfaces
Authors: Buckett M. I. , Marks L. D. 
Published: March 2011

ABSTRACTSurface-initiated radiation damage processes in a number of the maximum valence transition metal oxides - TiO2, V2O5, WO3, MoO3, Ta2O5, Al2O3, and Nb2O5 - have been investigated by in-situ high resolution electron microscopy under UHV conditions and at incident energies ranging from 3 keV to 300 keV. The relative contributions of ballistic, electronic, and thermal effects are evaluated by a comparison of the observed structural changes and damage rates - made under various experimental conditions of incident electron energy and flux - to theoretical predictions based on thermodynamic and available energy criteria.
The Behavior of Intersttitals in Irradiated Graphite
Authors: Pedraza D. F. 
Published: March 2011

ABSTRACTA computer model is developed to simulate the behavior of self-interstitials with particular attention to clustering. Owing to the layer structure of graphite, atomistic simulations can be performed using a large parallelepipedic supercell containing a few layers. In particular, interstitial clustering is studied here using a supercell that contains two basal planes only. Frenkel pairs are randomly produced. Interstitials are placed at sites between the crystal planes while vacancies are distributed in the two crystal planes. The size of the computational cell is 20000 atoms and periodic boundary conditions are used in two dimensions. Vacancies are assumed immobile whereas interstitials are given a certain mobility.Two point defect sinks are considered, direct recombination of Frenkel pairs and interstitial clusters. The clusters are assumed to be mobile up to a certain size where they are presumed to become loop nuclei. Clusters can shrink by emission of singly bonded interstitials or by recombination of a peripheral interstitial with a neighboring vacancy. The conditions under which interstitial clustering occurs are reported. It is shown that when clustering occurs the cluster size population gradually shifts towards the largest size cluster. The implications of the present results for irradiation growth and irradiation-induced amorphization are discussed.
In Situ Transmission Electron Microscope Studies of Ion Irradiation-Induced and Irradiation-Enhanced Phase Changes
Authors: Allen Charles W. 
Published: March 2011

ABSTRACTMotivated at least initially by materials needs for nuclear reactor development, extensive irradiation effects studies employing transmission electron microscopes (TEM) have been performed for several decades, involving irradiation-induced and irradiation-enhanced microstructural changes, including phase transformations such as precipitation, dissolution, crystallization, amorphization, and order-disorder phenomena. From the introduction of commercial high voltage electron microscopes (HVEM) in the mid-1960s, studies of electron irradiation effects have constituted a major aspect of HVEM application in materials science. For irradiation effects studies two additional developments have had particularly significant impact; (1) the development of TEM specimen holders in which specimen temperature can be controlled in the range 10–2200 K and (2) the interfacing of ion accelerators which allows in situ TEM studies of irradiation effects and the ion beam modification of materials within this broad temperature range. This paper treats several aspects of in situ studies of electron and ion beam-induced and enhanced phase changes and presents two case studies involving in situ experiments performed in an HVEM to illustrate the strategies of such an approach of the materials research of irradiation effects.
Small Lead and Indium Inclusions in Aluminium
Authors: Johnson E. , Hjemsted K. , Schmidt B. , Bourdelle K. K. , Johansen A. , Andersen H. H. , Sarholt-Kristensen L. 
Published: March 2011

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

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

ABSTRACTMultilayers of Y1Ba2Cu3O7-y/Y1Ba2(Cu1−xNix)3O7-ysuperconducting thin films have been grown epitaxially on (100) ZrO2 substrates using a pulsed laser deposition technique. The thickness of the Y1Ba2Cu3O7-y layer was varied from 60 Å to 900 Å and the thickness of the Y1Ba2(Cu1−xNix3O7-y layer was varied from 60 A to 100 A to determine the effect of the Ni-doped layers on the superconducting properties. Variations of critical current density were investigated as a function of temperature in magnetic fields up to 5 T. Magnetic field dependence of normalized critical current density, Jc(H)/Jc(O), is improved by the growth of Ni-doped multilayer structures, possibly due to an increase in flux pinning force.