Optical constants of amorphous Se

The pseudodielectric-function spectra, epsilon(E) = epsilon(1) (E) + i epsilon(2) (E), of amorphous (a-) selenium (Se) in the 1.2-5.2 eV photon-energy range at room temperature were measured by spectroscopic ellipsometry. The a-Se films investigated were deposited by vacuum evaporation in a base pressure of 2 x 10(-6) Torr on Si(100) substrates at room temperature. The epsilon(2) (E) spectrum showed only a broad peak at similar to 4 eV. Such a structureless feature is known to be typically observed in amorphous semiconductors. An ex situ atomic-force-microscopy image confirmed a microscopically flat surface (root-mean-square roughness of similar to 0.4 nm) with relatively sharp cones in spots. The Bruggeman effective-medium-approximation analysis suggested that the correction for this microroughness is very small (Delta epsilon(1,2)<0.2). The present epsilon(E) data and previously published data were used for the modeling of the optical constants of a-Se over the 0-15 eV photon-energy range. Dielectric-related optical constants, such as the complex refractive index, absorption coefficient, and normal-incidence reflectivity, of a-Se were also presented. (C) 1999 American Institute of Physics. [S0021-8979(99)03315-0].