Novel n-type conducting amorphous chalcogenide CdS.In2Sx:: an extension of working hypothesis for conducting amorphous oxides

Novel n-type conducting amorphous Cd-In-S chalcogenide have been prepared by extending a working hypothesis to explore transparent conducting amorphous oxide to chalcogenides. The de conductivity of the as-deposited samples is similar to 10(-4) S cm(-1) at 300 K and can be further increased to similar to 10(-2) S cm(-1) by heat treatment at temperature less than crystallization temperature. The activation energy of dark conductivity was similar to 0.3 eV in the as-deposited samples and similar to 0.13 eV for the annealed samples. Both activation energies are much less than the half of the Tauc optical band gap (similar to 2.2 eV). Variable-range hopping was observed in the annealed samples at temperatures below 40 K. The signs of Seebeck and Hall coefficients were negative, indicating that conduction is n-type and no sign anomaly was observed in the Hall voltage. We suggest that the Fermi energy is controllable by doping of carrier electrons via thermal formation of the anion vacancy as has been observed in amorphous ionic oxides such as Cd2PbO4. (C) 1998 Elsevier Science B.V. All rights reserved.