1.UPS involving core level photoemission peaks (Ga 3d for GaAs and Si 2p for Si)is measured for the (111), (110), (111),and (001)surfaces of GaAs and Si using thelight from a heliumlamp (21.2 eV and 40.8 eV) and from the Berlin synchrotron ra-diation source BESSY (108.6 eV),respectively.
