Electron affinity and band bending of single crystal diamond(111) surface

The electron affinity and band bending of a single crystal diamond (111) surface have been investigated as a function of hydrogen coverage via work function measurements, photoelectron yield spectroscopy, X-ray-excited photoelectron spectroscopy (XPS), and low-energy electron diffraction (LEED). The hydrogen desorption and the 1 x 1-2 x 1 surface phase transition were achieved by electron-beam irradiation at room temperature as well as annealing at high temperature. The electron affinity ranges from -1.27 eV for the fully hydrogen-covered 1 x 1 surface to 0.38 eV for the hydrogen-free 2 x 1 reconstructed surface. Electron beam irradiation is demonstrated to be an effective method to induce hydrogen desorption and surface reconstruction. However, this irradiation process does not change the surface band bending on type IIb diamond, which is generally increased by annealing. It is concluded that the electron-affinity change is caused by the C-II dipole layer, whereas the band bending is not directly related to hydrogen coverage or reconstruction but rather due to charged surface defects that are created simultaneously with the thermal treatment. (C) 1999 Elsevier Science S.A. All rights reserved.