OPTICAL PROPERTIES OF TELLURIUM IN FUNDAMENTAL ABSORPTION REGION

An analysis has been made of the optical absorption edge and reflectivity spectrum of single-crystal tellurium. Transmission measurements, using polarized light, were made between 10 and 300°K covering a range of absorption coefficient from 0.4 cm-1 to 5×103 cm-1. Below 100°K a sign reversal of the temperature coefficient of the absorption edge was observed for both directions of polarization. The lowabsorption region for Ec showed behavior indicative of indirect transitions, while the absorption edge for Ec varied exponentially with photon energy for over two decades. These features, together with the observation of an exciton at 0.336 eV for Ec, are similar in nature to those previously reported for trigonal selenium. Optical constants, such as the real and imaginary parts of the dielectric constant, have been calculated over a wide range of wavelengths at 10°K, as well as at 300°K, by applying the Kramers-Kronig relation to the reflectivity spectrum. © 1969 The American Physical Society.