Characterization of polycrystalline layers by channelling measurements

Abstract

From intenational conference on ion beam surface layer analysis; Yorktown Heights, NY (18 Jun 1973). Properties of polycrystalline Pd2Si layers formed on Si single-crystal substrates have been investigated by channeling measurements. Previous x-ray pole figure analysis indicated that the Pd2Si layers have a preferential orientation of the c-axis parallel to that of the axis of the substrate. The spread in crystallite orientations was found to depend strongly on heat treatment. The present measurements indicate that channeling minimum yields in these layers depend on this spread in orientation, and they show that channeling techniques can be used to obtain information on the orientation of polycrystalline films when the spread is of the order of the critical angle for channeling (~1 deg ). Minimum yields have been measured for protons and for 4He+ ions incident at energies from 0.2 to 2 MeV. Contrary to what is ordinarily observed for disordered single crystals, it was found that the minimum yields for the polycrystalline layers decrease markedly with decreasing beam energy. Assuming a gaussian distribution of crystallite orientations, calculations of the energy dependence of the minimum yield are consistent with the experimental findings.