Density Reduction: A Mechanism For Amortization at High Ion Doses

1993 ◽  
Vol 321 ◽  
Author(s):  
E. D. Specht ◽  
D. A. Walko ◽  
S. J. Zinkle
Keyword(s):  
Surface Density ◽  
Room Temperature ◽  
High Energy ◽  
Cryogenic Temperatures ◽  
Progressive Reduction ◽  
Near Surface ◽  
X Ray ◽  
Atomic Displacements ◽  
Density Reduction ◽  
High Doses

ABSTRACTAt cryogenic temperatures, the accumulation of vacancy-interstitial pairs in Al2O3 from atomic displacements associated with ion implantation produces amorphization. At room temperature, these pairs recombine, and amorphization occurs only at high doses. X-ray reflectivity measurements show that amorphization of the surface of Al2O3 implanted at room temperature with 160 keV Cr+ ions is preceded by a progressive reduction in near-surface density. Monte Carlo simulations show that this density reduction can be accounted for by high-energy-transfer collisions which knock atoms deep into the target, leaving widely separated vacancies and interstitials, which do not recombine. Electron Microscopy shows that at least some of these vacancies condense into voids. We propose that this reduction in near-surface density can lead to amorphization at high doses. We present simple approximations for the density reduction expected for different ions and targets.

scholarly journals Density Reduction: A Mechanism for Amorphization at High Ion Doses

1993 ◽  
Vol 316 ◽  
Author(s):  
E.D. Specht ◽  
D.A. Walko ◽  
S.J. Zinkle
Keyword(s):  
Surface Density ◽  
Room Temperature ◽  
High Energy ◽  
Cryogenic Temperatures ◽  
Progressive Reduction ◽  
Near Surface ◽  
X Ray ◽  
Atomic Displacements ◽  
Density Reduction ◽  
High Doses

ABSTRACTAt cryogenic temperatures, the accumulation of vacancy-interstitial pairs in Al2O3 from atomic displacements associated with ion implantation produces amorphization. At room temperature, these pairs recombine, and amorphization occurs only at high doses. X-ray reflectivity measurements show that amorphization of the surface of Al2O3 implanted at room temperature with 160 keV Cr+ ions is preceded by a progressive reduction in near-surface density. Monte Carlo simulations show that this density reduction can be accounted for by high-energy-transfer collisions which knock atoms deep into the target, leaving widely separated vacancies and interstitials, which do not recombine. Electron microscopy shows that at least some of these vacancies condense into voids. We propose that this reduction in near-surface density can lead to amorphization at high doses. We present simple approximations for the density reduction expected for different ions and targets.

Microstructure Evolution of a Fine Grain Al-50wt%Si Alloy Fabricated by High Energy Milling

2011 ◽  
Vol 479 ◽  
pp. 54-61 ◽  
Author(s):  
Fei Wang ◽  
Ya Ping Wang
Keyword(s):  
Grain Growth ◽  
Microstructure Evolution ◽  
Room Temperature ◽  
Milling Time ◽  
High Energy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Laser Method ◽  
X Ray ◽  
Fine Grain

Microstructure evolution of high energy milled Al-50wt%Si alloy during heat treatment at different temperature was studied. Scanning electron microscope (SEM) and X-ray diffraction (XRD) results show that the size of the alloy powders decreased with increasing milling time. The observable coarsening of Si particles was not seen below 730°C in the high energy milled alloy, whereas, for the alloy prepared by mixed Al and Si powders, the grain growth occurred at 660°C. The activation energy for the grain growth of Si particles in the high energy milled alloy was determined as about 244 kJ/mol by the differential scanning calorimetry (DSC) data analysis. The size of Si particles in the hot pressed Al-50wt%Si alloy prepared by high energy milled powders was 5-30 m at 700°C, which was significantly reduced compared to that of the original Si powders. Thermal diffusivity of the hot pressed Al-50wt%Si alloy was 55 mm2/s at room temperature which was obtained by laser method.

Silicon Carbide for Alpha, Beta, Ion and Soft X-Ray High Performance Detectors

2005 ◽  
Vol 483-485 ◽  
pp. 1015-1020 ◽  
Author(s):  
Giuseppe Bertuccio ◽  
Simona Binetti ◽  
S. Caccia ◽  
R. Casiraghi ◽  
Antonio Castaldini ◽  
...  
Keyword(s):  
High Performance ◽  
Room Temperature ◽  
Collection Efficiency ◽  
High Energy ◽  
Beta Particle ◽  
High Energy Resolution ◽  
Charge Collection Efficiency ◽  
X Ray ◽  
Current Densities ◽  
Full Charge

High performance SiC detectors for ionising radiation have been designed, manufactured and tested. Schottky junctions on low-doped epitaxial 4H-SiC with leakage current densities of few pA/cm2 at room temperature has been realised at this purpose. The epitaxial layer has been characterised at different dose of radiations in order to investigate the SiC radiation hardness. The response of the detectors to alpha and beta particle and to soft X-ray have been measured. High energy resolution and full charge collection efficiency have been successfully demonstrated.

Synchrotron X-ray Absorption Studies of Atomic-Level Alloying in Immiscible Mixtures

1998 ◽  
Vol 524 ◽  
Author(s):  
J.-H. He ◽  
P. J. Schilling ◽  
E. Ma
Keyword(s):  
Ball Milling ◽  
Room Temperature ◽  
High Energy ◽  
Atomic Level ◽  
High Energy Ball Milling ◽  
Edge Structure ◽  
X Ray ◽  
Energy Ball ◽  
Immiscible Mixtures ◽  
X Ray Absorption

ABSTRACTAn X-ray absorption beamline has been developed recently at the electron storage ring of the LSU Center for Advanced Microstructures and Devices. Using Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES), we have studied the local atomic environments in immiscible mixtures processed by high-energy ball milling, a mechanical alloying technique involving heavy deformation. By examining the local coordination and bond distances, it is concluded that atomic-level alloying can indeed be induced between Cu and Fe through milling at room temperature, forming substitutional fcc and bcc solid solutions. In addition to single-phase regions, a two-phase region consisting of fcc/bcc solutions has been found after milling at both room temperature and liquid nitrogen temperature. In contrast to the Cu-Fe system, solid solution formation is not detectable in milled Ag-Fe and Cu-Ta mixtures. This work demonstrates the power of synchrotron EXAFS/XANES experiments in monitoring nonequilibrium alloying on the atomic level. At the same time, the results provide direct experimental evidence of the capability as well as limitations of high-energy ball milling to form alloys in positive-heat-of-mixing systems.

X-ray study of the α–β transformation of berlinite (AlPO4)

1976 ◽  
Vol 54 (6) ◽  
pp. 638-647 ◽  
Author(s):  
H. N. Ng ◽  
C. Calvo
Keyword(s):  
Room Temperature ◽  
Translational Motion ◽  
Fold Axis ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Atomic Displacements ◽  
Β Phase ◽  
Four Corners ◽  
Dauphiné Twinning

The α–β transformation of berlinite (AlPO4) at 586 °C was studied by X-ray diffraction. Atomic displacements were obtained from results of least-squares refinement of data taken between room temperature and 600 °C using reflections whose intensity is unaffected by Dauphiné twinning. The results suggest a rotational motion of the PO4 and AlO4 tetrahedra around the two-fold axis together with a translational motion along the same axis as the transition is approached from below. The vibrational amplitudes of the atoms increase with temperature and have exceeded half of the separation between Dauphiné twin-related configurations at 500 °C. The final β-phase configuration is not achieved by this twinning due to the mismatch of the two configurational potential minima in the a direction. Analysis of the intensity vs. temperature data favours a single minimum model for the β phase configuration over an order–disorder model. The β-AlPO4 structure consists of alternate PO4 and AlO4 tetrahedra sharing all four corners with P—O and Al—O distances 1.505 and 1.694 Å respectively. The results are correlated with those obtained from temperature dependent studies by Raman scattering and by EPR on Fe3+-doped AlPO4.

Phase Transitions and Recrystallization in a Ti-46at%Al-9at%Nb Alloy as Observed by In-Situ High-Energy X-ray Diffraction

2006 ◽  
Vol 980 ◽  
Author(s):  
Klaus-Dieter Liss ◽  
Helmut Clemens ◽  
Arno Bartels ◽  
Andreas Stark ◽  
Thomas Buslaps
Keyword(s):  
Phase Transitions ◽  
Room Temperature ◽  
Strain Relaxation ◽  
Reciprocal Lattice ◽  
Lamellar Microstructure ◽  
High Energy ◽  
X Ray Diffraction ◽  
Orientation Relationships ◽  
X Ray

AbstractHigh-energy synchrotron X-ray diffraction is a powerful tool for bulk studies of materials. In this investigation, it is applied to the investigation of an intermetallic γ-TiAl based alloy with a composition of Ti-46Al-9Nb. The morphology of the reflections on the Debye-Scherrer rings is evaluated in order to approach grain sizes as well as crystallographic correlations. An in-situ heating cycle from room temperature to a temperature above the α-transus temperature has been conducted starting from a massively transformed sample. With increasing temperature the occurrence of strain relaxation, chemical and phase separation, domain orientations, phase transitions, recrystallization processes, and subsequent grain growth can be observed. During cooling to room temperature, crystallographic correlations between the re-appearing γ-phase and the host α-phase, known as the Blackburn correlation, are observed in the reciprocal lattice, which splits into different twinning and domain orientation relationships present in the fully lamellar microstructure.

scholarly journals Влияние термообработки на электрические характеристики полуизолирующих слоев, полученных с помощью облучения n-SiC высокоэнергетическими ионами аргона

2018 ◽  
Vol 44 (6) ◽  
pp. 11 ◽  
Author(s):  
П.А. Иванов ◽  
А.С. Потапов ◽  
М.Ф. Кудояров ◽  
М.А. Козловский ◽  
Т.П. Самсонова
Keyword(s):  
Heat Treatment ◽  
Silicon Carbide ◽  
Room Temperature ◽  
High Energy ◽  
Room Temperature Resistivity ◽  
Electrical Characteristics ◽  
Near Surface ◽  
Heat Treated ◽  
Argon Ions ◽  
Temperature Resistivity

AbstractIrradiation of crystalline n -type silicon carbide ( n -SiC) with high-energy (53-MeV) argon ions was used to create near-surface semi-insulating ( i -SiC) layers. The influence of subsequent heat treatment on the electrical characteristics of i -SiC layers has been studied. The most high-ohmic ion-irradiated i -SiC layers with room-temperature resistivity of no less than 1.6 × 10^13 Ω cm were obtained upon the heat treatment at 600°C, whereas the resistivity of such layers heat-treated at 230°C was about 5 × 10^7 Ω cm.

Epitaxial Growth of fee Fe and Cu Films on Diamond

1993 ◽  
Vol 313 ◽  
Author(s):  
D.P. Pappas ◽  
J.W. Glesener ◽  
V.G. Harris ◽  
J.J. Krebs ◽  
Y.U. Idzerda ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Energy ◽  
Copper Films ◽  
Face Centered Cubic ◽  
Continuous Film ◽  
X Ray ◽  
Cu Films ◽  
Face Centered ◽  
X Ray Absorption ◽  
Oriented Single Crystal

ABSTRACTThe growth of iron and copper films and multilayers on the (100) face of diamond has been achieved and studied by reflection high energy electron diffraction (RHEED), extended x-ray absorption fine structure (EXAFS), ferromagnetic resonance (FMR), and SQUID Magnetometry. RHEED and AES studies show that 2–3 atomic layers (AL) of Fe on C (100) forms a continuous film. The films as deposited at room temperature are disordered, and after a 350° C anneal displays a face-centered cubic structure. Subsequent layers of Cu on this epitaxial Fe film grow as an oriented, single crystal fee film. FMR and SQUID signals have been observed from the Fe films, showing that they are ferromagnetic.

Defect Pair Formation by Implantation-Induced Stresses in High-Dose Oxygen Implanted Silicon-on-Insulator Material

1993 ◽  
Vol 316 ◽  
Author(s):  
J.D. Lee ◽  
J.C. Park ◽  
D. Venables ◽  
S.J. Krause ◽  
P. Roitman
Keyword(s):  
Defect Density ◽  
Silicon On Insulator ◽  
Surface Strain ◽  
High Dose ◽  
X Ray Diffraction ◽  
Near Surface ◽  
X Ray ◽  
Density Reduction ◽  
Transmission Electron ◽  
Pair Density

ABSTRACTDefect 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.

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