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Shiv Nadar University

(SoNS) School of Natural Sciences

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.

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Physics

Fulltext

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.

Modern Physics Letters A

Generalized quantum conditions and coherent states

Using supersymmetry as a tool we set up a procedure to generate a sequence of pairwise isospectral potentials from a modified Crum-Darboux transformation. We show that such a transformation gives rise to shifted superpotentials much similar to what we encounter in a modified factorization scheme. We also explore some solvable systems to illustrate the applicability of our scheme. © World Scientific Publishing Company.

International Journal of Modern Physics A

Generating isospectral Hamiltonians from a modified Crum-Darboux transformation

Low resistivity Ni2Ge phase, a promising candidate as a contact and interconnect material for very large scale integrated circuit applications, has been synthesized by MeV ion beam mixing using Kr and Ar ions at and above room temperatures. Thin films of this phase produced by ion beam mixing show resistivity comparable to the one produced by thermal annealing and is much lower than that of many important suicides. The critical temperature which marks the beginning of the temperature dependent mixing is 326 K. The room temperature mixing efficiency for this system is found to be about an order of magnitude higher than the value predicted by any of the existing ballistic and spike models. The crystalline nature of the mixed region and the occurrence of the Ni2Ge phase have been discussed. © 1998 American Institute of Physics.

Journal of Applied Physics

Ion-induced room temperature synthesis of low resistive nickel germanide phase

The gene encoding the green fluorescent protein (gfp) under the control of the highly expressed Autographa californica nucleopolyhedrovirus (AcMNPV)- polyhedrin promoter has been introduced into the polyhedrin (polh) locus of Bombyx mori nucleopolyhedrovirus (BmNPV) by homologous recombination. The insect host larvae and the cultured cells infected with this recombinant virus (vBmGFP) showed high levels of expression of gfp. The larval tissues permissive to virus multiplication could be readily visualized using the tagged recombinant virus, thus providing a direct approach to study the progress of virus infection or its control in the animal host. The highly expressed recombinant protein, GFP, could be easily solubilized from fat bodies. Thus, the caterpillar-based expression could serve as an economic alternative method for the large-scale production of recombinant proteins, even when they are nonsecretory in nature. Further, if the recombinant vBmGFP is used as a parent in generating other recombinants, conversion of the fluorescent plaques to colorless plaques serves as an easy means for screening recombinants. Such a method is especially helpful for BmNPV- recombinant selections in the absence of the other simplified techniques as are available for the prototype baculovirus AcMNPV system.

Life Sciences

BioTechniques

Recombinant Bombyx mori nucleopolyhedrovirus harboring green fluorescent protein

Buried damaged layers in n-silicon created by implantation of MeV heavy ions has been studied by capacitance-voltage (C-V), current-voltage (I-V) and deep level transient spectroscopy (DLTS) techniques. In samples irradiated with doses below amorphization threshold, besides divacancy related trap, a new midgap acceptor trap level is isolated and shown to be responsible for carrier compensation. This defect level controls hysteresis in C-V characteristics and space charge limited current conduction in I-V characteristics. Possible origin of this defect have been discussed in the light of defect migration and cluster formation.

Defect level responsible for compensation in deep buried layers in n-type silicon

Hydrogen implantation in GaAs is performed. Depth profiling of H is also done using 1.38 MeV He+ ion induced ERDA. Isochronal vacuum annealing in the large range of 100-700°C is then conducted to study hydrogen migration. For as-implanted sample, simulation gives a total hydrogen content of 5.6 × 1016 at./cm2, with the peak located 1000 angstrom from the surface. An interesting change in the profile is observed at 400°C. The concentration under tail reduces significantly and the surface peak becomes sharper compared with the as-implanted peak, but the total hydrogen content remains almost the same. A net loss of hydrogen, indicating hydrogen out-diffusion is seen above 400°C.

Radiation Physics and Chemistry

Study of low energy plasma ion implanted hydrogen in GaAs

The 11A' and 21A' states of ozone are known to have a conical intersection near 83° in C2v, the intersection seam continuing into asymmetric geometries. We have calculated ab initio the symmetric stretch, antisymmetric stretch and bend components of the Born couplings between these states in the vicinity of the intersection seam, using MRD-CI wavefunctions and an analytical gradient formalism. All three components are significant and sharply peaked near the intersection seam. The non-adiabatic couplings in the vicinity of the energetically accessible conical intersection are expected to be important in understanding the spectroscopy of ozone in the region of the Huggins band. The conical nature of the intersection is illustrated. The singularity in the couplings is eliminated by constructing quasidiabatic states. Different diabatization schemes are discussed and compared. The quasidiabatic states are shown to have distinct characteristics. © 1998 Taylor & Francis Group, LLC.