Electrical resistivity of AgInSe2 films

Single-phase AgInSe2 ingot material, having the tetragonal chalcopyrite structure, was prepared by direct fusion of the constituent elements in vacuum-sealed silica tubes. Nearly stoichiometric films were prepared by thermal evaporation of the bulk material using a single source in 10−3 Pa vacuum on glass substrates. The chemical composition of the films was determined by energy-dispersive X-ray spectrometry, where the chemical formula could be represented by Ag(1−x)In(1−x/2)Se2(1+x) with x 0.02. All the deposited films exhibited n-type conduction. The temperature dependence of the dark electrical resistivity in the range 100–400 K revealed the dominance of the shallow donors below 150 K. A variable range hopping conduction mechanism due to localized state dominated in the range 150–200 K. At higher temperatures (200–300 K) grain boundaries effects dominated, whereas above 300 K extrinsic conduction due to impurities dominated.