An investigation of the depth profiles of deuterium implanted in copper

Abstract

Copper targets held at various temperatures are bombarded with a beam of monoenergetic deuterons. The products of the D (d,p) T reaction between bombarding deuterons and those already implanted in the target are detected with a surface barrier detector. The proton and triton energy spectra obtained are interpreted, using published energy loss data, reaction kinematics and differential cross-sections, to give the deuterium depth profiles. The target temperature is varied in the range -200°C to 160°C in an attempt to evaluate the temperature dependence of the concentration profiles. Fixed and variable temperature bombardment of the targets show two markedly different distributions of deuterium within the copper. At higher temperatures an appreciable proportion of the total deuterium in the target is found near the surface whereas at lower temperatures much of the deuterium remains deep in the target. In a particular target studied in detail the transition from one type of distribution to the other occurs over a narrow temperature range under conditions of deuteron bombardment. Scanning electron micrographs of the beam area following bombardment show sizeable blisters in the copper surface. The formation of a thin layer of deuterium at the surface of targets bombarded above -40°C is also noted. An explanation of these observations, with particular reference to the annealing behaviour of point defects in copper over the temperature range considered, is suggested.