APPLICATION OF DIRECTIONAL AES FOR NONDESTRUCTIVE DEPTH PROFILE ANALYSIS OF AN AU-CU ALLOY

Auger signals for a polycrystalline sample measured in an RFA spectrom eter depend on the incidence angle of the primary electron beam. As th is angle is increased, the proportion of the total Auger electron curr ent reaching the RFA collector is reduced but the total current increa ses. The resulting dependence is calculated in the framework of a simp le model for the sample consisting of a number of homogeneous layers o f different composition. Auger peak heights of Au and Cu are measured for incidence angles of 0 degrees and 60 degrees for Au and Cu standar ds, respectively, and for the Au0.4Cu0.6 alloy and comparison is made between those measurements and calculations performed for samples with different composition of two surface atomic layers. It is concluded t hat, after ion bombardment, the first atomic layer is enriched with go ld up to about 80%, while composition of the second layer is close to this in the bulk. After annealing the sample at T = 1000 K, sulphur an d copper segregate to the surface and concentration of gold in the fir st layer drops to zero. Those results are in a reasonable agreement wi th data available in the literature. (C) 1997 Elsevier Science Ltd.