SURFACE-STRUCTURES AND ELECTRONIC STATES OF H2S-TREATED INP(001)

We find two different surface structures, (1x2) and (1x1), for H2S-tre ated InP(001). They depend upon exposure of H2S at about 350 degrees C . The coverage of sulfur is estimated to be about a half monolayer and one full monolayer for the (1x2) and (1x1) structures, respectively. The (1x1) structure is reconstructed to the (1x2) structure upon annea ling at about 550 degrees C. It is suggested that sulfur is bonded to only In atoms and substitutes some of the phosphorus atoms below the f irst layer. Inverse photoemission spectra show strong reduction in int ensity of 1.2 eV peak above the Fermi level for a clean InP(001)-(4x2) surface upon adsorption of H2S. This reduction implies a decrease in unoccupied surface states due to dangling bonds of indium dimers on th e clean surface. The result of adsorption of oxygen on the (1x2) and ( 1x1) surfaces indicates significant passivation to oxidation of the su rfaces. (C) 1996 American Institute of Physics.