bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cracking And Aromatization Of Butanes Over ZSM-5 Zeolites
Authors: Ono Yoshio , Kanae Kunihiko , Osako Kazuaki , Nakashiro Katsumi 
Published: March 2011

ABSTRACTThe transformation of butanes over H-ZSM-5, Zn-ZSM-5, and Ga-ZSM-5 at 773 K were studied with special emphasis on the activation mechanism of butanes. Over H-ZSM-5, butanes undergo cracking exclusively by a carbonium-ion mechanism at low conversion levels. At higher conversion levels, the activation by a hydride-transfer mechanism are involved. The loading of Zn and Ga greatly enhances the dehydrogenation of starting alkanes as well as intermediate alkenes. The loading of the metal cations promotes also the cracking, especially in the case of isobutane. The synergetic action of the metal cations and protons is proposed as a mechanism of alkane dehydrogenation.
Selective Oxidation Of Hydrocarbons By Cobaltsubstituted Aluminophosphate Molecular Sieves
Authors: Maroni Victor A. , Iton Lennox E. 
Published: March 2011

ABSTRACTThe Co(III) form of cobalt-substituted aluminophosphate molecular sieves, Co(III)-APOs, was found to be a selective oxidant for a variety of organic and inorganic compounds. At relatively low temperatures (20 to 100°C), alcohols are converted to aldehydes and ketones, benzene becomes a dimer radical cation, amines are transformed to imines, and NO is oxidized to NO+. There is also evidence that Co(III)APOs activate the C-H bonds of methane at higher temperatures (400–500°C). Accompanying all these reactions is a clearly observable change of color from the yellow of the Co(III) form to the blue of the Co(II) form.
Strain Relief and Defect Formation in High Dose Oxygen Implanted Silicon
Authors: Venables D. , Jones K. S. , Namavar F. , Manke J. M. 
Published: March 2011

ABSTRACTLattice strain and defect formation in oxygen implanted silicon (SIMOX) were investigated as a function of dose and annealing conditions by high resolution x-ray diffraction and transmission electron microscopy. X-ray rocking curves revealed the presence of two distinct strained layers. Self-interstitial clusters and oxygen interstitials gave rise to a buried strain layer in unidirectional tension centered around the projected range at low doses (l×1016 and 3×1016 cm−2. As the dose was increased to 1×1017 and 3×1017 cm−2 a supersaturation of vacancies near the surface produced a second strain layer with a unidirectional lattice contraction at the wafer surface. Annealing at 900°C, 0.5 hr. reduced this surface strain as the defects coarsened into observable cavities. The development of cavities upon annealing was used in a sequential implantation and low temperature annealing process to produce low threading dislocation density SIMOX. Possible mechanisms for threading dislocation formation are discussed.
Feasibility of Simox Material Quality Determination Using Spectroellipsometry: Comparison With Raman And Planar View Transmission Electron Microscopy
Authors: Crean G. M. , Lyncrt S. , Greef R. , Stoemenos J. , Rossow U. , Richter W. 
Published: March 2011

ABSTRACTOne of the most promising silicon on insulator (SOI) fabrication techniques under development is Separation by IMplanted OXygen (SIMOX) substrates. The objective of this paper is to evaluate the feasability of employing spectroscopic ellipsometry (SE) for the determination of SIMOX substrate quality. Defect density measurements obtained from planar view transmission electron microscopy (TEM) studies are presented and concur with the Raman experimental results. The need for the development of a more sophisticated ellipsometric optical response model to mirror the complexity of the annealed Si overlayer microstructure is demonstrated.
The Energy Dependence of Ion Damage in A1xGa1−xAs/GaAs HETErostructures and The Effects of Implanted Impurity
Authors: Cullis A. G. , Jacobson D. C. , Polman A. , Smith P. W. , Poate J. M. , Whitehouse C. R. 
Published: March 2011

ABSTRACTBombardment damage produced by Si+ ions in AlxGa1−xAs/GaAs layer structures has been studied using transmission electron microscopy and ion channeling and backscattering spectrometry. The damage resistance of A1xGa1−xAs alloy layers increases with Al concentration. In particular, by comparison of complementary Si+ ion doses yielding similar nuclear displacement densities at 150keV and 2MeV bombardment energies, it is demonstrated for the first time that the local concentration of implanted Si impurity is likely to be a significant factor in controlling lattice damage build-up, especially for the highest Si+ ion implantation doses. It is also shown that, in a manner analogous to A1As, the alloy layers can confer a significant protection from ion damage upon adjacent, epitaxially-bonded narrow zones of crystalline GaAs.
Anisotropic Damage Production at ION Irradiated GaAs/AlAs Interfaces
Authors: Klatt J. L. , Alwan J. , Coleman J. J. , Averback R. S. 
Published: March 2011

ABSTRACTIon beam mixing and damage production at GaAs-AlAs interfaces was studied by Rutherford backscattering and channeling methods. It was observed that the general features of the intermixing of GaAs with AlAs at 100K are typical of that in other semiconductor and metallic systems but that the damage production is not. The GaAs layers amorphize at a very low ion dose whereas the AlAs layers are very resistant to amorphization. Damage in the AlAs begins at one interface of the GaAs and grows through the AlAs layer, but damage at the other interface never nucleates. The ratio of nuclear to electronic stopping influences the growth of the damage zone.
Characterization of Novel Emissions in Mg+ -Implanted InP
Authors: Iida Tsutomu , Makita Yunosuke , Niki Shigeru , Yamada Akimasa , Asakura Hisao , Kimura Shinji , Obara Akira , Uekusa Shin-ichiro 
Published: March 2011

ABSTRACTPhotoluminescence (PL) measurements have been carried out as a function of temperature and of excitation power on heavily magnesium (Mg) implanted ultra-pure indium phosphide (InP) with a dose concentration, [Mg], ranging from l×lO15cm-3 to 3×1020cm−3. Several undefined emissions have been observed; a strong emission, Z, emerges near the band-acceptor emission for [Mg]= 3×1020cm−3 and two novel emissions, Y1 and Y3 appear below the energy of donor-acceptor pair emission for [Mg] smaller than 3×1018cm−3. In order to obtain more explanation on such emission, temperature and excitation power dependence of the emissions were investigated. Temperature dependent PL experiments revealed that Z is composed of three emissions named ZA, ZBand ZC. Measured activation energies suggest Z represents a pair type transition associated with Mg acceptors. While, Y1 and Y3 emissions are attributed to donor-acceptor type transition because of a significant blue-shift with increasing excitation power.
Mesotaxy Layers of IrSi3 in (111)Si Formed by MeV ION Implantation
Authors: Short K. T. , White Alice E. , Eaglesham D. J. , Jacobson D. C. , Poate J. M. 
Published: March 2011

ABSTRACTIridium has been implanted at 1MeV and 500keV in the dose range 1 to 3×1017/cm2 at 525°C to form a buried Ir-rich region ∼ 2500Å below the surface in (111)Si. Samples were annealed at temperatures in the range 600°C to 1200°C to form buried IrSi3 layers. Rutherford backscattering and channeling analysis in conjunction with transmission electron microscopy were used to study the formation and the alignment of the IrSi3 layer to the silicon host as a function of annealing. For a dose of 2×1017 Ir/cm2, stoichiometric IrSi3 formed beneath ∼ 2000Å of Si after annealing to 1100°C. The IrSi3 layer was aligned with the Si substrate with Xmin ∼12%, but a band of precipitates remained either side of the main layer.
Formation of Buried Epitaxial Si-Ge Alloy Layers in Si <100> Crystal by High Dose Ge ION Implantation
Authors: Yu Kin Man , Brown Ian G. , Im Seongil 
Published: March 2011

ABSTRACTWe have synthesized single crystal Si1−xGex alloy layers in Si <100> crystals by high dose Ge ion implantation and solid phase epitaxy. The implantation was performed using the metal vapor vacuum arc (Mevva) ion source. Ge ions at mean energies of 70 and 100 keV and with doses ranging from 1×1016 to to 7×1016 ions/cm2 were implanted into Si <100> crystals at room temperature, resulting in the formation of Si1−xGex alloy layers with peak Ge concentrations of 4 to 13 atomic %. Epitaxial regrowth of the amorphous layers was initiated by thermal annealing at temperatures higher than 500°C. The solid phase epitaxy process, the crystal quality, microstructures, interface morphology and defect structures were characterized by ion channeling and transmission electron microscopy. Compositionally graded single crystal Si1−xGex layers with full width at half maximum ∼100nm were formed under a ∼30nm Si layer after annealing at 600°C for 15 min. A high density of defects was found in the layers as well as in the substrate Si just below the original amorphous/crystalline interface. The concentration of these defects was significantly reduced after annealing at 900°C. The kinetics of the regrowth process, the crystalline quality of the alloy layers, the annealing characteristics of the defects, and the strains due to the lattice mismatch between the alloy and the substrate are discussed.
Ion Implantation of High Doses of Co in Si1−xGex Alloys
Authors: Lauwers A. , Maex K. , Vandervorst W. , Brijs G. , Poortmans J. , Caymax M. , Vanhellemont J. , Petersson S. 
Published: March 2011

ABSTRACTThe implantation of high doses of Co in Si1−xGex alloys is investigated for several Ge concentrations. The aim of this work is to monitor phase formation, layer formation and crystalline structure of the layers. The samples are evaluated by RBS, SIMS, TEM and sheet resistance measurements. Similar as for the implantation of high doses of Co in Si, buried layer formation of CoSi2 in the Si1−x Gex alloy is observed with a concommitant expulsion of Ge out of the silicide layer.
Process and Simulation of TiSi2/n+/p Silicon Shallow Junctions
Authors: Wu Ying , Savin W. , Fink T. , Ravindra N. M. , Lareau R. T. , Pfeffer R. L. , Yerke L. G. , Wrenn C. 
Published: March 2011

ABSTRACTExperimental analysis and simulation of the formation and electrical characterization of TiSi2/+/p-Si shallow junctions are presented here. The formation of shallow n+-p junction, by ion implantation of As through Ti films evaporated on p-Si substrates followed by Rapid Thermal Annealing (RTA) and conventional furnace annealing has been performed in these experiments. Structural techniques such as Secondary Ion Mass Spec-troscopy (SIMS) and Rutherford Backscattering (RBS) experiments have been employed to characterize these devices. RUMP simulations were used to analyze and interpret the RBS data. Current-voltage characteristics have been simulated using PISCES simulator.
A Novel Process to Form Epitaxial Si Structures With Buried Silicide
Authors: Erokhin YU. N. , Grotzschel R. , Oktyabrski S. R. , Roorda S. , Sinke W. , Vjatkin A. F. 
Published: March 2011

ABSTRACTThe interaction during low temperature thermal annealing of metal atoms from a Ni film evaporated on top of Si structures with a buried amorphous layer formed by ion implantation has been investigated. Rutherford Backscattering Spectrometry (RBS)/channeling, cross-sectional transmission electron microscopy (XTEM) and X-ray microanalysis were used to determine structures and compositions. It is shown that the combination of such silicon properties as the increased rate of silicidation reaction for amorphous silicon with respect to the crystalline one in combination with high metal atom diffusivity leads to formation of buried epitaxial Ni silicide islands at the interface between the amorphous and the top crystalline silicon layers. During thermal annealing at temperatures as low as 350° C, these islands move through the a-Si layer leaving behind epitaxially recrystallized Si.
Temperature Dependence of Ar Sputtering of CoSi2 Thin Films on Si and SiO2
Authors: Hong Q. Z. , Harper J. M. E. 
Published: March 2011

ABSTRACTThe temperature dependence of 300 eV argon ion sputtering of CoSi2 thin films in the range 50–600°C has been investigated. At temperatures above 400°C, the etch rate of CoSi2 on Si is significantly reduced, while the underlying Si reacts with the Co atoms diffusing from the silicide surface. As a result, the silicide layer effectively moves into the substrate during Ar bombardment. During sputtering of CoSi2 on Sio2, the thickness of the silicide layer decreases almost linearly with bombarding time until all the silicide is removed. Similar behavior is observed in low temperature sputtering of CoSi2 on (100) Si and evaporated Si. However, at elevated temperatures (400°C< <600°C), sputtering of CoSi2 on Si undergoes two consecutive stages. During the initial stage, the thickness of the silicide layer decreases at the same rate as that of the silicide on SiO2, and is accompanied by an enrichment in Co concentration near the surface. During the second stage, the etch rate of the silicide is reduced to only one third of the rate during the initial stage.
Ion Beam-Induced Amorphization of (Mg, Fe)2SiO4 Olivine Series: An In Situ Transmission Electron Microscopy Study
Authors: Wang L. M. , Ewing R. C. 
Published: March 2011

ABSTRACTEffects of ion beam irradiation of five members of the (Mg, Fe)2SiO4 olivine series, from synthetic pure fayalite (Fe2SiO4) to naturally occurring (Mg0.88Fe0.12)2SiO4, have been studied by in situ transmission electron microscopy (TEM). Under 1.5 MeV Kr+ ion room temperature irradiations, all of the samples have been amorphized. The critical amorphization dose or the total collision energy loss required for amorphization increased rapidly with the increasing Mg:Fe ratio which coincides with an increasing melting temperature (bond strength) and an increasing average bond ionicity. A 400 keV He+ ion irradiation of (Mg0.88Fe0.12)2-SiO4, which mainly results in ionization energy loss in the sample, did not cause amorphization even at a much higher dose rate and a much higher final dose. This indicates nuclear interactions (collisions) are primarily responsible for ion beam induced amorphization. Also, high resolution electron microscopy (HREM) images of the defect structure at a low ion dose have been obtained and compared with the displacement cascade structure generated by computer modelling.
Characterization of Ion Irradiated Zirconia-Yttria Films
Authors: Huang N. K. , Feng Z. R. , Xiong Z. K. , Wang D. Z. , Wang P. L. 
Published: March 2011

ABSTRACTZirconia-yttria films containing 8.0wt% Y2O3 were prepared on a Si substrate with r.f. magnetron sputtering deposition followed by 170 KeV Ar+ ion irradiation at room temperature. The characterization of these zirconia-yttria films with different ion bombarding doses has been studied by XRD, XPS and AES. It was found that all the films consisted of three portions, the amorphous films deposited with r.f. magnetron-sputtering were partially crystallized and nontransformable tetragonal (T') phase was detected after Ar+ ion bombardment of a dose of 1×1016 ion/cm2, and the oxidized states of Zr3d, Y3d and Ols peaks of XPS were observed under the conditions of argon ion bombardment of different doses.
MeV Self Ion Beam Induced Amorphisation of Silicon Carbide Surfaces and Its Effect on Their Trdbomechanical Propertdzs
Authors: Sood D. K. , Nath V. C. , Xi Yang 
Published: March 2011

ABSTRACTAmorphisation of sintered SiC by bombardment with self (C, Si) ions has been studied. Ion doses ranged from 1×1015 to 1×1017 ions/cm2; and ion energy was varied from 0.09 to 5 MeV. Amorphisation was detected by micro-focus Raman scattering. Tribomechanical properties-friction and wear were studied with a high precision pin (steel ball) and disc (implanted) machine. Results show substantial improvements in friction and wear, which persist to a large number of cycles. Tribomechanical properties are shown to correlate with surface amorphisation and carburisation. Carbon ions are found to be much more effective than Si ions (with similar damage distributions) in reducing friction and wear.
Stability of Uranium Silicides During High Energy Ion Irradiation
Authors: Birtcher R. C. , Wang L. M. 
Published: March 2011

ABSTRACTChanges induced by 1.5 MeV Kr ion irradiation of both U3Si and U3Si2 have been followed by in situ transmission electron microcopy. When irradiated at sufficiently low temperatures, both alloys transform from the crystalline to the amorphous state. When irradiated at temperatures above the temperature limit for ion-beam amorphization, both compounds disorder, with the Martensite twin structure in U3Si disappearing from view in TEM. Prolonged irradiation of the disordered crystalline phases results in nucleation of small crystallites within the initially large crystal grains. The new crystallites increase in number during continued irradiation until a fine grain structure is formed. Electron diffraction yields a powder-like diffraction pattern that indicates a random alignment of the small crystallites. During a second irradiation at lower temperatures, the small crystallizes retard amorphization. After 2 dpa at high temperatures, the amorphization dose is increased by over twenty times compared to that of initially unirradiated material.
Role of Chromium in High-Dose, High-Rate, Elevated Temperature Nitrogen Implantation of Austenitic Stainless Steels
Authors: Williamson D. L. , Ivanov I. , Wei R. , Wilbur P. J. 
Published: March 2011

ABSTRACTIn order to help establish the role of Cr in high-dose, high-dose-rate, elevated temperature N implantation of austenitic (fcc) stainless steels, similar implantations into fee Ni80Fe20 and Ni80Cr20 alloys have been made and characterized by Auger depth profiling and X-ray diffraction. For the Ni-Fe alloy a shallow layer fcc(∼ 0.2 μm) containing an ordered fee γ'-(Ni0.8Fe0.4)4N phase is induced. In contrast, for the Ni-Cr alloy a much thicker N-containing layer (∼ 0.2 μm) is produced consisting primarily of a high-N solid solution fee phase. The fractions of the implanted N retained in Ni-Fe and Ni-Cr were approximately 10 and 100%, respectively. The mechanisms by which Cr is promoting the deep migration and high retention of N in solid solution are proposed.
Photoluminescence of Erbium in Amorphous Silicon: Structural Relaxation and Optical Doping
Authors: Custer J. S. , Snoeks E. , Polman A. 
Published: March 2011

ABSTRACTPhotoluminescence of erbium in ion-implanted amorphous Si has been observed after annealing at 400°C. In addition, a broad band of luminescence attributed to intrinsic defects in amorphous Si is present. The background level steadily increases with increasing anneal temperature. The fluorescence lifetimes of either the Er or the background in all samples are ≤150μsec.
Metastable Phase Formation in the Y-TI System by Ion Mixing
Authors: Lai S. L. , Zhang Z. J. , Ding J. R. , Liu B. X. 
Published: March 2011

ABSTRACTAmorphization behavior was studied for the Y-Ti system, which has rather positive heat of formation being around + 22 kJ/mol, by room temperature 360 keV xenon ion mixing of YxTi100−xmultilayered films to various doses, ranging from 7×1014 to 1×1016 xe/cm2 Single and uniform amorphous phase was obtained in a narrow composition region, i.e. x=65 to 75, after ion mixing to the relevant doses. Moreover, a metastable fee crystalline Y-Ti phase was observed, for the first time, in this system. The crystalline lattice constant of the metastable phase was determined to be 4.012 Å. The re-crystallization temperature of the formed amorphous alloy was found out to be 600°C by in situ transmission electron microscope annealing as well as by vacuum furnace experiments. Possible interpretation is also discussed by comparing the experimental results with those proposed models for predicting glass forming ability.
Al-Yb Amorphous Alloys Produced by Ion Mixing or Solid State Reaction
Authors: Liu B. X. , Ding J. R. , Che D. Z. , Zhang H. B. 
Published: March 2011

ABSTRACTWe report, in this paper, three different ways of producing amorphous alloys in the Al-Yb system, (i) Al80Yb20multilayered films were readily amorphized by 180 keV xenon ion mixing at room temperature(RT) to a dose of 3×1015 Xe/cm2. (ii) When the dose went up to 1×1016 Xe/cm2 or higher, a metastable phase of hcp structure was formed. Interestingly, the hcp phase turned into amorphous after annealing at 500°C for about 10 minutes. (iii) Amorphous alloys were also formed by steady state thermal annealing of the Al-Yb multilayered films at about 450 °C for 20 minutes. The optimum amorphization range was found out by experiments to be 17 to 30 Yb at%, i.e., within this composition range, the multilayered films could entirely be amorphized by solid state reaction.The recrystallization behavior of the amorphous alloys formed by different methods was also studied and the difference in this aspect was thought to relate to the structures resulting from different processing methods.Possible explanation of the observed sequence of phase transition is also discussed.
Molecular Dynamics Simulation of Electron Irradiation-Induced Amortization of the Ordered Compound NiZr
Authors: Devanathan R. , Lam N. Q. , Sabochick M. J. , Okamoto P. R. , Meshh M. 
Published: March 2011

ABSTRACTWe present the results of a molecular dynamics simulation of the crystalline-to-amorphous transformation in the ordered intermetallic compound NiZr, using embedded-atom potentials. It is found that NiZr can be amorphized by random atom exchanges as well as by the introduction of Frenkel pairs. In both cases, the shear elastic constants C44 and C decreased drastically and eventually became equal. The average shear elastic constant fell to about 40% of its original value. These results are in general agreement with experimental observations.
Nanoindentation Hardness of 17–4PH Stainless Steel Irradiated With 2.5 MEV PER Nucleon 20NE2+ Ions
Authors: Grummon D. S. , Schalek R. , Rachel T. , Schock H. , Ronningen R. M. , Mcharris Wm. C. 
Published: March 2011

ABSTRACTDirect ion implantation of radioactive isotopes, such as 7Be or 22Na, has recently been of interest as a means of surface layer activation for purposes of wear-rate measurement in material systems for which activation by conventional proton irradiation is ineffective. Though direct implantation doses anticipated for adequate wear measurement sensitivity are expected to be quite low (∼1012 cm−2), the potential for alteration of wear properties by ion damage cannot be ignored. The present work was designed to simulate 22Na implantation with non-radioactive 20Ne irradiations into specimens of 17–4PH stainless steel which had been deliberately heat treated to contain 98 vol% metastable martensite. Specimens were subjected to doses of 2×1012, 2×1013 and 2×1014 cm−2 of 20Ne2+, applied at a total energy of 50 MeV, giving a projected ion range (determined by TRIM-91 computations) of approximately 10 μm. Nanoindentation surface hardness traverses were conducted to detect any material softening which may have resulted from ion-solid interactions within the projected range. Though doses of > 1014 cm−2 produced a detectable softening (apparent as a dip in the hardness level corresponding to locations near the end of the ion range) the maximum dose for a negligible effect on nanoindentation hardness was found to be approximately 1013 cm−2, well above the doses anticipated for use in wear studies employing direct ion implantation of radioisotopes.