Conversion of crystalline germanium to amorphous germanium by ion bombardment

Abstract

Of particular interest in the theory of radiation damage are the size and structure of the damaged regions produced in crystalline solids by fast particle irradiation. In the present work crystalline germanium at room temperature or at 30°K has been bombarded in a Siemens electron microscope with 100 kev oxygen ions emanating from oxide-coated emission filaments. The size and structure of the damaged regions generated by the incident ions have been examined at both temperatures using transmission electron microscopy. Detailed evidence is presented which shows that the damaged regions had a size which was dependent on the temperature of the specimen during bombardment and a structure which was amorphous and less dense than the crystalline matrix in which they were located. Further, as the ion dose was increased to 2 × 10¹⁵ ions cm⁻² the entire surface region to a depth of ∼600 Å was observed to undergo a gradual transition from a crystalline to an amorphous state. In terms of radiation damage models these results are shown to be consistent with the concept of a temperature spike superimposed on a depleted zone.