Heat treatment effects on the structural and electrical properties of thermally deposited AgIn5S8 thin films

The heat treatment effects on structural and electrical properties of thermally deposited AgIn5S8 thin films have been investigated. By increasing the annealing temperature of the sample from 450 to 500 K, we observed a change in the crystallization direction from (420) to (311). Further annealing of the AgIn5S8 films at 550, 600 and 650 K resulted in larger grain size in the (311) preferred direction. The room temperature electrical resistivity, Hall coefficient and Hall mobility were significantly influenced by higher annealing temperatures. Three impurity levels at 230, 150, and 78 meV were detected for samples annealed at 350 K. The electrical resistivity decreased by four orders of magnitude when the sample annealing temperature was raised from 350 to 450 K. The temperature dependent electrical resistivity and carrier concentration of the thin film samples were studied in the temperature ranges of 25–300 K and 140–300 K, respectively. A degenerate–nondegenerate semiconductor transition at approximately 180 was observed for samples annealed at 450 and 500 K. Similar type of transition was observed at 240 K for samples annealed at 600 and 650 K.

Research highlights
► Heat treatment effects on the electrical and structural properties of AgIn5S8 films are studied.
► A grain size enhancement associated with change in preferable orientation direction is detected.
► A degenerate–nondegenerate semiconductor transition has been achieved by annealing.
► A carrier mobility improvement is obtained by heat treatment.