Atomic and electronic structure of epitaxial PbS on InP 110/ and InP 001/

Thin films of PbS have been deposited on InP 110.and InP 001.surfaces. Epitaxial growth of the films was obtained already at room temperature RT.. Low-energy electron diffraction LEED.patterns according to the PbS 001.surface were obtained on both substrate orientations. This result indicates a rather good lattice match on InP 001., while an incommensurate lattice matching was observed alongw001xon InP 110.. Core level photoemission studies have demonstrated that an abrupt interface forms at the 110.substrate orientation, while an interface reaction occurs on the In-terminated InP 001.-2=4 superstructure after PbS deposition. The electronic structure of PbS films was studied experimentally by using angle-resolved ultraviolet photoemission spectroscopy ARUPS.and theoretically by applying supercell calculations on the density functional theory level in the local density approximation DFT-LDA.. The supercell calculations indicate surface rumpling and inward relaxation as well as the existence of up to three surface-related states on PbS 001.. The experimental data for PbS bulk and thicker PbS films coincide well and agree reasonably with the simulations. The dispersion of the electronic states in ultrathin PbS films 2 nm. is significantly suppressed in comparison to bulk, indicating the incomplete development of the bulk-derived electronic states. q2000 Elsevier Science B.V. All rights reserved