Physics

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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.

(SoNS) School of Natural Sciences

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.

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Journal of Applied Physics

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

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.

Proceedings of SPIE - The International Society for Optical Engineering

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

Squeezed states for parabosons are constructed since we know that a parabose oscillator can be parametrized in terms of bosonic operators. We also discuss some of their important properties.

Modern Physics Letters A

Squeezed states for parabosons

Exploiting the Lax form of the Korteweg-de Vries equation, we determine the whole set of its symmetry operators and relate them to conserved quantities. We also study a KdV supersymmetric version and put in evidence its even (bosonic) and odd (fermionic) symmetries. We then get the Lie superalgebra characterizing this supersymmetric nonlinear equation. © World Scientific Publishing Company.

Generating symmetry operators for the KdV equation and seeking their supersymmetric generalizations

The results of MeV Kr+ ion-beam mixing of Au in amorphous metallic alloy Fe78B13Si9 at room temperature for various doses are presented. The mixing rate found experimentally does not correlate with prediction of current phenomenological models which consider the influence of ballistic and thermodynamic parameters of the mixing.

MeV ion beam mixing of Au in Fe78B13Si9 amorphous metallic alloy

This paper reports on the atomic transport occurring across the interface of Cu/Ge and Co/Ge layers leading to the synthesis of Cu3Ge and Co2Ge phases under MeV Kr and Ar ion irradiations. These phases have potential applications in modern semiconductor device technology. The marker experiments show that in the case of Cu/Ge systems both Cu and Ge are mobile but Cu is the dominant moving species. On the other hand, in the case of the Co/Ge system only Ge atoms are mobile. The atomic movements during ion irradiation in these two systems have been explained on the basis of distribution of defect density and effects of thermodynamic forces. © 1998 Elsevier Science S.A. All rights reserved.

Thin Solid Films

Atomic transport in Cu/Ge and Co/Ge systems during ion-beam mixing

We have studied trapping kinetics of defects during carrier capture in heavily damaged silicon, where damage was induced by MeV heavy ions at doses near but below the amorphization threshold. Using spectroscopic junction transient measurements, we provide unambiguous evidence of charge redistribution between defects. These results imply that changes in the occupancy of gap states are responsible for the deepening of emission energies with filling time, as is commonly observed in transient experiments in disordered silicon. This is in contrast to its usual explanation in terms of deepening of energy states due to hierarchical defect relaxation. © 1998 The American Physical Society.

Physical Review B - Condensed Matter and Materials Physics

Charge redistribution among defects in heavily damaged silicon

The propagation of the carbon plumes in argon atmosphere used for film growth by pulsed laser ablation deposition (PLAD) is studied using ion probe. Spatial and angle resolved analysis of plasma parameters as a function of argon gas pressure is presented. The electron temperature is strongly dependent on the angle with target surface normal as well as the distance from the target surface. The forward directed nature of the PLAD process is strongly influenced by the pressure of the ambient gas. The plasma parameters are used to explain the effect of ambient gas pressure on the characteristics of the deposited film.