Observations of electron reflection at tungsten (001) surface in the energy range 1–10 eV

Abstract

Measurements of electron reflection at tungsten (001) surface are reported. The measurements were made with a display-type LEED apparatus operated in the retarding mode. Results are given for clean tungsten and for surfaces formed by adsorption of gases on tungsten. The variation of diffraction intensity (arbitrary units) as a function of electron energy in the range 1–10 eV is described for the 00 and 01 beams. Measurements on clean tungsten are reported for a sequence of values of the angle of incidence ψ0, for each of two azimuthal orientations of the primary beam (0 and 45° referred to the 01 direction in the crystal surface). The measurements on the 00 beam fill in the gap between those of Khan, Hobson and Armstrong and of Zollweg for normal incidence (ψ 0 = 0) and those of Propst and Edwards (ψ 0 = 53°) and are correlated with these earlier measurements. The chief observations are: A — a narrow peak near 4 eV which is insensitive to both variation of primary-beam orientation and gas adsorption; B — a very narrow dip-peak combination whose location can be correlated with the 01 beam threshold (grazing-emergence) energy and whose location and shape are highly sensitive to gas adsorption. The observations support suggestions that A is connected with an inelastic-scattering threshold and that B is a surface-state resonance.