SIMULATION OF SURFACE-ROUGHNESS EFFECTS IN ERDA

The program SURF has been developed to simulate surface roughness effe cts in elastic recoil detection analysis (ERDA). The Program calculate s the recoil energy spectrum from a sample with a rough surface from a superposition of spectra, each corresponding to a subdivision of the beam spot. All parameters which influence the depth resolution are tak en into account. The algorithm was tested successfully on well defined periodic structures which were produced by ion etching of Si. Recoil energy spectra measured with 200 MeV I-127 ions of samples with random roughness exhibit two characteristic features: large broadening and l ower yield in the high energy region. Both features are well reproduce d in the simulated spectra, from which the variance of the statistical roughness can be deduced. The program can assist in the understanding of surface roughness effects, and enable such effects to be identifie d in concentration depth profiles. (C) 1998 Elsevier Science B.V.