Low resistivity annealed tin-doped zinc oxide thin films prepared by the sol gel technique

Abstract

Tin-doped zinc oxide films were obtained by mixing zinc oxide and tin oxide precursor solutions by the sol–gel technique. The tin atomic concentrations in the solution studied were 0, 2, 4, 6, 8 and 10 at %. The films were deposited by the dipping method on glass substrates. The films were sintered at 400 °C for 1 h, in an open atmosphere. A second thermal treatment in vacuum (~10-3 torr) at 500 °C for 5 min was applied in order to decrease the resistivity of the films. The X-ray diffraction patterns show the hexagonal phase of ZnO. The crystalline grain size decreases as the tin content increases. SEM measurements show a change in morphology surface when tin is added. All films show high optical transmission (~85%) and a direct band gap value of 3.2 eV. The minimum resistivity value obtained was 10-1 Ω-cm for the films with 4 at. % of tin.