Recoil selection by pulse shape discrimination in elastic recoil detection analysis with α-particles ( α-ERDA)

In elastic recoil detection analysis (ERDA) with a-particles, recoils can be separated from scattered projectiles by using detectors with a thin depletion layer and a pulse shape discrimination (PSD) circuit [S.S. Klein and H.A. Rijken, Nucl. Instr. and Meth. B 66 (1992) 393]. Improved performance is obtained with a multi-parameter data acquisition system; recoil events are more easily and accurately selected and sensitivity is improved by a factor of 5 to 1 X 1014 at/cm2 for oxygen on amorphous silicon. The typical surface depth resolution is 10 nm. Two alternative PSD circuits are proposed neither of them using fast electronics. Examples are given of profiling carbon and oxygen in thin films of Si, C and SiOxNy.