Lack of Photoemission Evidence for Tailing of Density of States into Energy Gap of Amorphous Si

A photoemission study of amorphous Si for 5. 5<~<~11. 7 eV has been made with emphasis placed on checking an earlier report of photoemission evidence for a tailing of the density of states into the energy gap. A comparison of photoelectron energy distribution curves from amorphous Si with those of Au and crystallized Si yielded no evidence for tailing of the density of states. It is concluded that the large tailing of the density of states previously reported is not an intrinsic property of amorphous Si but probably a result of the different sample preparation. In both our amorphous and crystallized Si films the Fermi level is located 0. 28 0. 05 eV above the valence band maximum at the surface.