A Compact High-performance Helium Atom Scattering Apparatus for Surface Studies

We describe a very compact apparatus developed for high resolution studies of surface structure and phonon spectroscopy by means of diffraction and inelastic scattering of a supersonically cooled He atom beam. The angular and energy resolutions for the specularly reflected beam are 0.13° and ΔE = 0.4 meV, respectively, for an incident energy of E i = 22 meV. The process of modification of the surface structure by thermal desorption of adsorbates, or irradiation by electron, radical, and ion beams, can be monitored non-destructively under UHV conditions by measurements of the scattered intensity of He atoms. The performance of the apparatus is assessed by measurement of He diffraction and inelastic scattering from the low index single crystal surfaces of copper. The potential of the apparatus for kinetic studies of surface reactions is demonstrated for reduction of a copper oxide surface by a H atom beam.