Formation of thin film of AB compound layer under irradiation

Abstract

In this research study, we proposed a model that describes the formation of thin-film of an AB compound layer at the interfaces of two immiscible solid layers A and B under the influence of irradiation. However, we begin our study with a non-irradiation process where we investigate the growth kinetics of an AB compound layer under the diffusion of one and two kinds of species. This diffusion process takes place by means of one or two transport mechanisms during an AB compound layer formation process. The results that follow from this investigation reveal a complex growth kinetics of an AB compound layer under the diffusion of two kinds of species by means of two transport mechanisms. However, the complex growth behaviour transforms to simple linear-parabolic or parabolic growths when only one kind of species diffuse by means of one transport mechanism. In the irradiation aspect of the study, the A and B solid layers (bilayer system) are considered to be bombarded by a beam of light and heavy energetic particles independently under different considerations. We take into account two possibilities during the irradiation of this bilayer system. Firstly, the majority of the kinetic energy of the radiation particles is considered to be converted into heat energy which subsequently results in the heating of the irradiated layers. We assume that the energy transferred from the incident particles to the atoms of the irradiated materials during the course of irradiation is less than their lattice threshold displacement energy. Thus, no defects are generated during this process. The influence of heating that accompanies the irradiation process is investigated to see if it could accelerate the growth of an AB compound layer at the interfaces of the A and B layers. The second possibility is considered under the presupposition that the kinetic energy transferred by the radiation particles is greater than the lattice threshold displacement energy of the A and B layers; therefore, this process results in defects generation. The contribution of the two basic point defects (i.e. interstitial and vacancy defects), induced by irradiation, towards the growth of an AB compound layer is studied independently. The results that follow from this study show that the rate of growth of an AB compound layer at the interfaces depends on the defect generation rate. The growth rate increases proportionally with the defect generation rate. At high-temperature irradiation, the growth rate depends strongly on both temperature and defect generation rate while at lowtemperature irradiation it depends strongly only on defect generation rate. On the other hand, the radiation heating makes no significant contribution towards the growth of an AB compound layer at low temperature; this is because the dimensions of the A and B layers that are considered in this study are in the order of a few tens of nanometers. Considering the fact that the amount of energy deposited by the radiation particles increases with the thickness of the irradiated layer, less energy is, therefore, deposited in the irradiated layers under the thin film consideration. This reason makes radiation heating a less probable process for an AB compound layer formation under the influence of irradiation.