OPTICAL STUDIES OF DISORDER AND DEFECTS IN AMORPHOUS GEXSE1-X FILMS AS A FUNCTION OF COMPOSITION

The optical absorption edges of as-deposited evaporated a-GexSe1-x, fi lms. with x = 0, 20, 33, 43 and 50 at%, have been accurately determine d down to 0.6 eV from a combination of optical and PDS experiments. Th e results are analyzed as a function of composition in terms of chemic al ordering, strain-induced disorder and coordination defects, taking the pure constituents and the stoichiometric GeSe2 compound as referen ces.