Physics

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Shiv Nadar University

The iron di-silicide β-FeSi2 is a promising direct band gap semiconductor but difficult to produce. Here, the successful direct synthesis of this phase by ion beam mixing of Fe/Si bilayers at temperatures in the range of 450 to 550°C is reported. The obtained single-phase β-FeSi2 layers and their structure are confirmed by Rutherford backscattering spectrometry, X-ray diffraction and conversion electron Mossbauer spectroscopy.

World University root node

(SoNS) School of Natural Sciences

Applied Physics A: Materials Science and Processing

Direct synthesis of β-FeSi2 by ion beam mixing of Fe/Si bilayers

Inspired by the possibility of factorizing the second derivative interwining operators using a modified form of the well-known Crum-Darboux transformation, we pressent a scheme for generating a new pair of isospectral potentials. We also consider the interesting problem of constructing coherent states for such factorizable operators.

Modern Physics Letters A

Higher derivatives supersymmetry, a modified Crum-Darboux transformation and coherent state

We study the problem of pseudoscalar mixing in an (Formula presented) breaking framework. In this connection, we derive the condition of a vanishing (Formula presented) component in the η,(Formula presented) wave functions. We also obtain new constraints obeyed by the mixed decay constants (Formula presented) which determine the octet-singlet mixing angles. In the (Formula presented) sector we find from a fit to the radiative decay rates of mesons that the presence of a (Formula presented) admixture in (Formula presented) is small in disagreement with the point of view that the branching ratio of (Formula presented) is enhanced by (Formula presented) mixing. © 1999 The American Physical Society.

Physical Review D - Particles, Fields, Gravitation and Cosmology

Mixing angles and decay constants of η, [formula presented], and [formula presented]

We study the problem of pseudoscalar mixing in an SU(4)xSU(4)xUA(1) breaking framework. In this connection, we derive the condition of a vanishing cc̄ component in the η,η′ wave functions. We also obtain new constraints obeyed by the mixed decay constants fη,η′q (q=u,s), which determine the octet-singlet mixing angles. In the ηη′ ηc sector we find from a fit to the radiative decay rates of mesons that the presence of a cc̄ admixture in η′ is small in disagreement with the point of view that the branching ratio of B→η′ K is enhanced by η′ ηc mixing. ©1999 The American Physical Society.

Mixing angles and decay constants of η, η′, and ηc

We study chiral and UA(1) phase transition in the dilute gas approximation. A comprehensive analysis of the mass and mixing angel of η and η′ reveals that in the transition of the quark-gluon-plasma droplets to the hadrons, besides the chiral phase transition, the UA(1) phase transition also plays a significant and non-trivial role. © 1999 Elsevier Science B.V. All rights reserved.

Fulltext

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

Chiral and UA(1) phase transitions in QCD: An analysis of the I = 0 pseudoscalars

We report on the evaluation of ion-beam induced damage in α-quartz and its dynamic annealing behavior in the temperature range between 80 and 1050 K using Rutherford backscattering spectrometry in channeling geometry. The results illustrate that the critical temperature for inhibiting amorphization during irradiation is about Tc≈940 K. The critical fluence φc for amorphization is independent of the temperature up to 550 K, but strongly increases at higher temperatures. The activation energy for the diffusion of defects in the collision cascade or at the amorphous/crystalline interface is found to be 0.28±0.02 eV. The dynamic annealing mechanism is explained by the vacancy out-diffusion model of Morehead and Crowder. © 1999 American Institute of Physics.

Journal of Applied Physics

Ion-beam induced amorphization and dynamic epitaxial recrystallization in α-quartz

The epitaxial α-quartz thin film could be a promising material for fabricating optical devices because of its unique optical and mechanical properties and processing advantages compared to bulk materials. This letter reports on the solid-phase epitaxial growth of thin amorphous SiO2 films deposited by electron gun evaporation on single-crystalline α-quartz substrates. This was achieved by high-dose Cs+-ion implantation and subsequent thermal annealing in air. Also, a thin amorphous layer produced by Si+-ion implantation on a-quartz was epitaxially regrown, thus indicating that the epitaxy is independent of the preparation history of the amorphous layer. The results are explained on the basis of network modifications induced by alkali and oxygen in the SiO2 structure. © 1999 American Institute of Physics.

Applied Physics Letters

Epitaxial crystallization of amorphous SiO2 films deposited on single-crystalline α-quartz

The temperature dependence of the amorphization in α-quartz by Ne-ion bombardment has been investigated using Rutherford Backscattering Spectrometry in channeling geometry (RBS-C). The experimental results show that the critical temperature Tc for inhibiting amorphization in quartz is around 940 K. The damage depth profile χ3(z, φ) is independent of the temperature and fluence and can be simulated with a power-law function [χ(z, φ) α (φFD(z))3] of the damage energy distribution FD (z). At low irradiation temperature, the critical dose φc for amorphization is independent of the temperature but it strongly increases at higher temperatures with an activation energy of 0.28 eV and has been explained by out-diffusion model of Morehead and Crowder. © 1999 Elsevier Science B.V. All rights reserved.

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Temperature dependence of ion-beam induced amorphization in α-quartz

This paper reports on the changes occurring in the concentration versus depth profiles of hydrogen in undoped semi-insulating (SI) GaAs (100) crystals. DC plasma ion implanted SI-GaAs samples were isochronally annealed in vacuum in the range of 100-350 °C. Hydrogen depth profiling has been performed by elastic recoil detection analysis technique. The changes in the H profiles have been explained on the basis of migration of hydrogen towards the defect-rich region produced during plasma ion implantation.

Proceedings of SPIE - The International Society for Optical Engineering

Study of plasma ion implanted hydrogen in semi-insulating GaAs

We consider possible modifications of the Calogero-Vasiliev quantum condition and address the problem of construction of coherent states.