Ion beam induced amorphisation in semiconductors studied using perturbed angular correlations

Ion implantation is an increasingly important technique in the fabrication of semiconductor devices. The understanding of irradiation produced disorder is thus of important scientific and technological significance. While many techniques have been applied to the study of semiconductor materials, no single method can provide a full characterisation and a detailed understanding of the physical processes relies on the application of a diverse range of complimentary techniques. In this paper we discuss the application of the Perturbed Angular Correlation technique to the study of ion beam amorphisation in semiconductor materials. The Perturbed Angular Correlations (PAC) method uses radioactive atoms at very low concentrations to provide information about the local electronic or magnetic structure around the probe atom. It relies on the change in the radiation pattern observed when an excited nucleus decays in an extra-nuclear field. A good description of the fundamental principles of the PAC method and its application to semiconductors is provided by the recent review of Wishart (1). The current measurements have used the n In probe nucleus. This nucleus I decays via electron capture to the daughter, 1HCd which is formed in an excited state. This nucleus then de-excites by the emission of two y-rays. It is the perturbation of the y-y angular correlation of these two y-rays by the presence of non zero electric field gradients at the probe site which is observed in the current measurements