BAND-GAP ENERGIES OF SEMICONDUCTING SULFIDES AND SELENIDES

Thin films of some semiconducting sulphides (ZnS, CdS and Bi2S3) and s elenides (ZnSe, CdSe and Bi2Se3) have been prepared using the chemical deposition method. The band gap energy of the films was determined by optical absorption measurements while the activation energy was deter mined from resistance measurements. The band gap energies obtained fro m the absorption measurements ranged from 1.42 eV for Bi2Se3 to 3.72 e V for ZnS while the activation energies obtained from the resistance m easurements ranged from 0.31 eV for Bi2Se3 to 0.59 eV for ZnSe. The hi gh optical band gap obtained for the films could be attributed to very small size in chemically deposited films which lead to electrical iso lation of individual grains, or quantum well structure. The small valu es of the activation energies are due to the presence of impurity leve ls in the energy band gap of the films. (C) 1998 Elsevier Science S.A. All rights reserved.