Defects and their range in pure bismuth irradiated with swift Xe ions studied by positron annihilation techniques

Jerzy Dryzek,Krzysztof Siemek

doi:10.1007/s00339-018-2367-x

Jerzy Dryzek, Krzysztof Siemek

Open Access

https://doi.org/10.1007/s00339-018-2367-x

Copy DOI

Abstract

Investigations of defects and their spatial distribution in Bi irradiated with 167 MeV Xe26+ ions of different doses have been performed using conventional positron lifetime spectroscopy and variable energy positron beam. In an implanted layer, in which ions are traveling, interacting with atoms and stopping, only clusters which consist of more than eight vacancies were found. It was assigned from ab initio theoretical calculations of positron lifetime in vacancy clusters in Bi. The thickness of this layer corresponds to the range of implanted ions calculated from the SRIM code. However, beyond this layer, an extended layer with such defects has also been found. Its thickness is comparable to the thickness of the implanted layer and it depends on the dose. Defects induced by implantation are also present near the entrance surface, and their concentration depends on the dose of implanted ions as well. Three methods for reconstructing the actual mean positron lifetime and thus the induced depth defect distribution have been proposed, two of them are used in current research.

Highlights

Introduction and motivationMany aspects of swift ion–solid interactions have been intensively studied, including the morphology of atomic defects generated during this interaction [1]
To detect the depth profile of defects resulting from implantation, the sample was etched to remove a layer of about 2 μm thick and the positron lifetime spectrum was measured. 25% solution of nitride acid in distilled water was chosen as an etching solution
The procedure was subsequently repeated until the bulk value of the positron lifetime was obtained, this means that the damage layer has been removed and the virgin region has been reached

Summary

Introduction

Introduction and motivationMany aspects of swift ion–solid interactions have been intensively studied, including the morphology of atomic defects generated during this interaction [1]. It is generally accepted that defects are generated mainly at the end of the ion track results from inelastic nuclear collision cascades when ion energy is of the order of keV. This takes place in the nuclear stopping power regime. According to the thermal spike model, strong coupling of excited electrons with phonons results in rapid heating and cooling of the material in the vicinity of the track. This leads to a transient and highly disordered zone [2].

Objectives

Results

Conclusion