NANOSCALE IN-DEPTH MODIFICATION OF CR-O-SI LAYERS

In-depth modification of Cr-O-Si layers on a nanoscale has been perfor med by low energy inert (Ar+, He+) and reactive (N-2(+)) ions. Chemica l and short range structural investigations were done by XPS. Cr and S i were essentially oxidised in the as-prepared (i.e. virgin) samples. Ar+ bombardment led to a nearly complete reduction of Cr to Cr-0. At t he same time, about one third of the oxidised Si was converted to Si-0 , which was shown to form Si-Cr bonds. Also, silicide type clusters, p redicted earlier by XPS, have been identified by glancing angle electr on diffraction. He+ bombardment led to an increase of the surface O co ncentration. This was manifested also in the disruption of Si-Cr bonds formed by the preceding Ar+ bombardment and conversion of Cr and Si p redominantly to Cr3+-O, Cr6+-O and Si4+-O. With N-2(+) bombardment for mation of Cr-N and Si-N bonds was observed. The thickness of the trans formed surface layers were about 5 nm, 9 nm and 30 nm for Ar, N and He projectiles as estimated by TRIM calculations. The observed transform ations were interpreted in terms of the relative importance of sputter ing or ion induced mixing for Ar+ and He+, and also by the role of the rmodynamic driving forces.