ELECTRICAL-RESISTIVITY OF AGINSE2 FILMS

Single-phase AgInSe2 ingot material, having the tetragonal chalcopyrit e structure, was prepared by direct fusion of the constituent elements in vacuum-sealed silica tubes. Nearly stoichiometric films were prepa red by thermal evaporation of the bulk material using a single source in 10(-3) Pa vacuum on glass substrates. The chemical composition of t he 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 less than or equal to 0.02. All the deposited films exhibited n-type conduction, The temperature dependence of the dark electrical r esistivity in the range 100-400 K revealed the dominance of the shallo w donors below 150 K. A variable range hopping conduction mechanism du e to localized state dominated in the range 150-200 K. At higher tempe ratures (200-300 K) grain boundaries effects dominated, whereas above 300 K extrinsic conduction due to impurities dominated.