Electrical properties of electron irradiated CdSe thin films

Polycrystalline cadmium selenide thin films, 38 μm thick, were prepared by single-source thermal evaporation method on optical glass substrate. Structural analysis revealed a wurtzite type structure, with (111) preferential orientation perpendicular to the substrate. The films were irradiated with high energy electrons (6 MeV) at room temperature, to a fluence of 1015 e-/cm2 and their conductivity and photo-conductivity were measured between 150 and 300 K. There are two defect levels that mostly influence the electrical behavior of the films, located at 0.14 eV and 0.4 eV below the conduction band edge. An unusual type of I-V characteristics was recorded, i.e. a decrease of the conductivity with the applied voltage. A tentative explanation is given for such an effect. (authors)