OPTICAL-PROPERTIES OF PBS

Spectroscopic ellipsometry has been used to measure the complex dielec tric function epsilon(E) = epsilon(1)(E) + i epsilon(2)(E) of PbS sing le crystals. The measurements are made on cleaved PbS surfaces in the 1.5-5.3 eV photon-energy range at room temperature. It is found that t he optical properties of PbS are very sensitive to air exposure. The o bserved epsilon(E) spectra reveal distinct structures at energies of t he E-1, E-2, and E-3 critical points (CPs). These data and the literat ure values are used for the modeling of the optical constants of PbS o ver the 0.3-5.3 eV photon-energy range, including the band-gap (E-0 si milar to 0.4 eV) region. It is shown that the three-dimensional M-0 CP (E-0) and damped harmonic-oscillator model (E-1, E-2, and E-3) provid e satisfactory fits to the experimental optical-constant data. (C) 199 8 American Institute of Physics. [S0021-8979(98)05411-5].