Interstitial Atom Location in Silicon by Single and Double Alignment Backscattering of MeV Helium Ions

Abstract

Single alignment and double alignment back- scattering of helium ions from silicon have been simulated in a computer model. The dependence of the backscattering yield profiles on the tilt plane is examined for single alignment along and the (110), (111), and (100) tilt planes for 2.1 MeV helium ions with a beam divergence of 0.04°. For off axis interstitial sites maxima in the yield profiles are found at angles which are characteristic of the particular site. In double alignment the yield profiles of 2.8 MeV helium ions backscattered from a silicon crystal with 5.10-3 interstitial silicon atoms per lattice atom are calculated for the combinations: incidence channeling, \( \left\langle {1\bar 10} \right\rangle \) blocking direction with detector tilt in (110) and \( \left\langle {\bar 100} \right\rangle \) blocking direction with detector tilt also in (011). The former combination is sensitive to tetrahedral, hexagonal, and Yb positions and the latter to hexagonal. The lowest interstitial concentration to be detected is estimated to be 10−3. The efficiency of the double alignment in determining the configuration of lattice defects is compared with that of single alignment.