Low Energy Ion Bombardment Effects in Supersaturated Copper-Indium Alloys.

Scanning transmission electron microscopy and Auger electron spectroscopy were used to investigate the effects of low energy (200 - 3000 eV) Ar('+) ion bombardment of supersaturated Cu:In alloys. Ion bombardment always resulted in the preferential sputtering of In although for sample temperatures T(,s) (GREATERTHEQ) 250(DEGREES)C, In loss due to preferential sputtering was increasingly compensated by radiation-assisted surface segregation. Even at room temperature, however, the steady state In concentration in the altered layer during irradiation, while reduced, remained supersaturated and enhanced diffusion to ion bombardment -created point defect sinks resulted in the volume precipitation of randomly dispersed In-rich (delta) phase ((TURN) 30at%In) particles in the near-surface region. Thermally induced precipitates, on the other hand, nucleated only at grain boundaries and were only observed at T(,s) (GREATERTHEQ) 250(DEGREES)C. The average size and number density of radiation-induced precipitates increased with increasing ion bombardment energy E(,i). Upon termination of ion bombardment at T(,s) (GREATERTHEQ) 250(DEGREES)C, the In surface concentration always returned to (TURN) 30at%. The recovery time for this process decreased with increasing T(,s) and E(,i) due to fast diffusion through near-surface regions containing residual damage such as dislocation loops. The measured widths of the compositionally altered layers were on the order of the ion penetration range.