Angle-resolved and -integrated photoemission from a ZnSe (110) surface

Abstract

Angle-resolved and -integrated photoemission spectra from the ZnSe(110) surface were measured with He I (21.2 eV) light. Angle-resolved spectra were taken for the ? -?′, ? -?, and ? -? symmetry lines. From oxygen-contamination tests and by comparing the experimental result with a calculated surface electronic structure, we expect both surface and bulk states to contribute to the emission spectrum. The dispersion of the surface states at ∠−1.0 eV (energy zero is taken at the valence-band maximum) near the ?′ point and at ∠−1.5 eV near the ? point are reproduced by the calculation, while the presence of the surface state at −4 eV near the ? point is not predicted by the calculation. The Se-s-like surface state is detected at ∠0.5–1.0 eV above the upper edge of the lower valence band. The emission features due to valence-band states are interpreted by a model which disregards conservation of the wave vector perpendicular to the surface. The energies of the valence-band states at the X, W, and L critical points are determined: X5 = −2.5, X3 = −5.25, W2 = −3.4, W1 = −5.1, and L1 = −5.7 eV.