Photoemission from some metals and semiconductors in the energy range 5--350 eV

During the last year we have used synchrotron radiation from the Stanford Synchrotron Radiation Project (SSRP) to perform uv and soft x-ray photoemission studies of metals and semiconductors in the energy range 5--350 eV. Here, we report on some of the results for Au, Cu, W, and GaAs. An interesting observation for Au is the modulation of the valence-band spectrum for photon energies of 100--200 eV. Furthermore, we illustrate (for the Au 4f levels) the feasibility of doing detailed studies on the energy dependence of the photoionization cross sections with a tunable light source. The relative cross section for the Cu 3p and 3d electrons is drastically different for excitation energies of 200 and 1500 eV, respectively. The distribution curves of the valence band of a tungsten surface covered with an ordered layer of graphite show strong energy and angular dependence. The oxidation properties of GaAs(110) surfaces have been studied by observing chemical shifts of the Ga and As 3d levels. It appears that oxygen forms bonds with As, and not Ga, surface atoms during the first stage in the chemisorption