ELECTRICAL AND OPTICAL STUDIES IN Ge100-xSx CHALCOGENIDE THIN FILMS

H.S. Metwally Physics Department, Faculty of Education, Ain Shams University Roxy, Cairo, Egypt

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Received: December 8, 2000; revised version April 10, 2001

Thin films of Ge100-xSx with different values of x are deposited on quartz substrates by a conventional thermal evaporation technique. The electrical conductivity of these films was measured. The experiments reveal that the electronic conduction is strongly composition dependent and is thermally activated with a single activation energy for x>40. A variable range hopping conduction mechanism seems to dominate when x=16 and 27. The optical absorption of the films is investigated using spectrophotometric measurements of the transmittance and reflectance in the wavelength range 200-3000 nm. All the studied compositions obey the Tauc relation concerning the non-direct transitions. The optical energy gap Eg value increases with the increase in chalcogen content x. The Urbach parameter E0 decreases from 310 meV to 149 meV as x increases from 16 to 70.

DOI: 10.12693/APhysPolA.99.683 PACS numbers: 73.61.Jc, 78.66.Jg