PB GAAS(100) - BAND BENDING, ADATOM-INDUCED GAP STATES AND SURFACE DIPOLE/

The work presented here shows a correlation between the position of Pb -induced gap states, responsible for the initial movement of the Fermi level (E(F)) at the Pb-GaAs(100) interface, and the position of the P b 5d core level measured by photoemission spectroscopy. The difference in Pb-induced pp states is obtained by depositing submonolayer amount s of Pb on the As-rich (2 X 4)-C(2 X 8) or the Ga-rich (4 X 2)-C(8 X 2 ) GaAs(100) surfaces. These reconstructions are known to produce a lar ge dipole-induced difference in the work function of the clean surface . The correlation suggests that the reconstruction-induced dipole is m ostly preserved during the initial stage of Pb deposition and shifts t he energy levels of the adsorbate.