Solid-State Detector for Low-Energy Ions

Abstract

The electrical properties of a polished surface of high-purity silicon can be greatly modified by heavy ion bombardment. In particular, the change in the rectifying properties of silicon has been used as a detector of low energy ions striking the surface. By bombarding with He+ ions through a silver film which was evaporated directly on the silicon, we determined the thickness of Ag at which ions no longer reached the silicon surface. By this method it was found that the range of 30 kev He+ ions in Ag films is 2480±250 A. The lowest ion energy which produces an observable effect on the silicon is about 200 ev. Similar effects have been observed for hydrogen, argon, nitrogen, and oxygen ions. Other electrical properties of silicon surfaces which have possibilities as ion indicators are mentioned.