A METHOD FOR THE DETERMINATION OF ATOMIC DISPLACEMENTS IN COMPOUND-CRYSTALS BY MEANS OF RBS PIXE CHANNELING EXPERIMENTS

A method which combines proton-induced X-ray emission (PIXE), Rutherford backscattering (RBS) and ion channeling, which enables the determination of static or dynamic root-mean-square displacements of constituent atoms in compound crystals is described. Full PIXE and RBS channeling angular scan curves are measured simultaneously by scanning through a major axis of the crystal under study. The experimental data are interpreted by using two different methods: A) a simple semi-analytical model which takes advantage of the depth information contained in RBS spectra to estimate depth correction factors needed to analyze the PIXE angular scan data, and B) a Monte Carlo simulation program of channeling, which takes into account the special structural features of the materials studied and allows for a direct comparison of simulated results with experimental PIXE data. The use of the technique is demonstrated by deducing rms displacements of constituent atoms of some II-VI (binary and ternary) semiconductors analyzed by both methods. The present results agree well with vibrational amplitude data obtained from X-ray diffraction measurements available from the literature.