Papers by Author: Aman Deep Acharya

Abstract: The diffusion trapping model has been applied to slow positron annihilation in He+ irradiated polystyrene and polystyrene – polystyrene bilayers. The S-parameter and the positron lifetime have been calculated as a function of the incident positron energy. The effect of the fluence upon the nature of the S-parameter curve has been discussed. It has been found that a change in fluence affects positronium formation. The transition rate for surface to positronium formation has been found to be dependent upon the fluence and the atomic number of the irradiated ion. The lifetime results show that, at low energy, the o-Ps annihilates mainly at the polymeric surface. The free volume hole concentration is found to decrease at low energy, and becomes constant at higher energies.

Abstract: The Diffusion Trapping Model has been used to obtain the positron annihilation Doppler broadening lineshape parameter in ZnO and O+, B+, N+, Al+ implanted ZnO films. The concentration of vacancy clusters is found to be related to the atomic number and the fluence of the implanted ion. The S-parameter is found to be largest in the case of implantation of Al+ ions and is minimum for the implantation of B+ ions. Thus, the vacancy clusters are found to be largest in the case of Al+ implantation. The calculated results have been compared with the experimental value.