UHV Systems for Surface Studies by Ion Scattering

Abstract

Two UHV systems have been built for studies of solid surfaces by ion backscattering in the energy ranges (a) 0.5–50 keV and (b) 100–300 keV on separate ion accelerators. The UHV systems are similar in most respects except that (b) has LEED optics. The stainless steel chamber with integral pumping system encloses a goniometer in which the sample can be rotated and tilted for alignment of a crystal axis with the beam. The sample can also be translated across the beam. The energies of backscattered ions are measured in an electrostatic analyzer which has three independent motions to allow the analyzer to be precisely aimed at the beam spot on the sample. The chamber sits on a table which can be adjusted vertically and horizontally. Samples can be inserted conveniently through a 3.8 cm side port and attached to the goniometer with a special tool. Special problems encountered in mating a UHV system to an ion accelerator will be discussed. Results of measurements in system (a) have been reported [D. J. Ball, T. M. Buck, D. MacNair, and G. H. Wheatley, Surface Sci. 30, 69 (1972)].