ANALYSIS OF PHOTOEMISSION AND INVERSE-PHOTOEMISSION SPECTRA OF SI(111) AND SULFUR-PASSIVATED INP(001) SURFACES

Photoemission (PES) and inverse-photoemission spectra (IPES) for the s ulphur-passivated InP(001) surface are compared with theoretical predi ctions based an density-functional calculations. As a test case for ou r methods, we also present a corresponding study of the better known S i(111) surface. The reported spectra for InP(001)-S agree well with th e calculated ones if the surface is assumed to consist of a mixture of two phases, namely, the fully S-covered (2X2)-reconstructed structure , which contains four S atoms in the surface unit cell, and a (2X2) st ructure containing two S and two P atoms per unit cell. The latter has recently been identified in total-energy calculations as well as in c ore-level spectra of S-passivated InP(001) surfaces under annealing. T he experimental IPES for Si(111)-(2X1) is in excellent agreement with the calculations. The comparison of the experimental PES with our calc ulations provides additional considerations regarding the nature of th e sample surface. It is also found that the commonly used density-of-s tates approximation to the photoemission and inverse-photoemission spe ctra is not valid for these systems. [S0163-1829(97)09040-1].