The characterization of randomly stepped surface of copper by helium backscattering

The elastic backscattering of a thermal energy helium nozzle beam by (100), (110), (111) faces of a copper single crystal which has been electrochemically roughened, is studied. The intensity of the specular peak as a function of the incidence angle or incident energy shows a sequence of maxima and minima. Their positions are very well described by the Bragg relation assuming that interferences occur between beams reflected from terraces separated by steps the heights of which are equal to separation of two adjacent basic planes. From the amplitude of these extrema it is possible to calculate the statistical distribution of terrace widths. The results are in a good agreement with the estimation which can be deduced from the macrogeometric profile measured by light interferometry. (Auth.)