On the amorphizatxon of Si and WO 3 by particle impact

Abstract

Estimates of the depth of bombardment-induced amorphization (R_a ) are presently available for seven different ions injected into Si (Ar, As, B, Ne, P, Sb and Si) as well as for Kr injected into WO₃. These depths can be interpreted in terms of recent damage-distribution theories to yield F_d (R_a ), the initial displacement fraction at depth Ra. (Here the term ‘initial’ means ‘present before thermal and athermal annealing’.) The resulting values of F_d (R_a ) were found to be reasonably constant, such that, depending on which theory was used, they had an average of either 0.7 ±0.2 or 0.4 ±0.2 for Si and either 0.09 ±0.03 or 0.17 ±0.06 for WO₃. This approximate constancy is considered to be particularly significant with Si, since the data used encompassed incident masses from 11 to 122, incident energies from 10 to 280 keV, and doses from 3 × 10¹⁴ to 1 × 10¹⁴ ions/cm². It is concluded, in view of the constancy of F_d (R_a ), that the amorphization of si and WO₃ can be self-consistently explained by homogeneous damage accumulation. An alternative category of explanation, based on the random impingement of discrete disordered regions of volume V_a is, however, not excluded; in fact, it is argued that the constancy demonstrated here for F_d (R_a ) is also compatible with discrete disordered regions provided V_a is proportional to the incident energy E.