Plasma-Enhanced Chemical Vapour Deposition of Amorphous Se Films

The preparation of layers of amorphous Se by plasma-enhanced CVD using the hydride H 2 Se as precursor gas is described. Using a mixture of 15 vol.% H 2 Se in H 2 , 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 Se g molecular fragments. The optical transmission spectrum was recorded at different temperatures in the range 77-300 K. The optical bandgap E r was calculated from the optical absorption coefficients α using Tauc law: αhυ = C(hυ-E T ) 2 , where hυ is the photon energy. The temperature dependence of E T can be approximated by a linear relation: Δ/E T (T 2 -T 1 = -7.6 x 10 -4 x (T 2 -T 1 ).