Plasma-Enhanced Chemical Vapour Deposition of Amorphous Se Films

Abstract
The preparation of layers of amorphous Se by plasma-enhanced CVD using the hydride H₂Se as precursor gas is described. Using a mixture of 15 vol.% H₂Se in H₂, partly crystallized films were obtained. Information concerning the structure of the films was obtained from Raman spectroscopy. The spectra of amorphous Se indicated that the dominant molecular structure is the eight-membered ring and/or a chain with Se₈ molecular fragments. The optical transmission spectrum was recorded at different temperatures in the range 77-300 K. The optical bandgap E_T was calculated from the optical absorption coefficients α using Tauc law : αν=C(hν-Er)², where hν is the photon energy. The temperature dependence of E_T can be approximated by a linear relation : [MATH].