Optical interband spectra and band structure of Ru2Si3 and Ru2Ge3

Among the semiconducting silicides Ru2Si3 is considered to be an attractive material for optoelectronic and thermoelectric applications. However, only few papers on the electronic properties exist. Here we report results of o ptical investigations of this semiconducting material and its analogon Ru2G e3 by spectroscopic ellipsometry in the spectral range of 0.7-10 eV and by UV-vis-near infrared (NIR) transmission and reflectivity measurements. The optical spectra for Ru2Si3 and Ru2Ge3 exhibit semiconducting character with dominant interband features around 2 and 5 eV and a relative minimum in th e joint density of interband states between 3 and 4 eV. More pronounced str uctures were found for single crystalline samples than for solid phase crys tallized thin films. The dielectric functions are compared with theoretical calculations of the optical properties which have been carried out using t he LMTO-ASA method. Good agreement has been found between theory and experi ment for the spectral distribution of optical constants. (C) 2000 Elsevier Science S.A. All rights reserved.