Effect of the sputtering time on the characteristics of p-SnOx:Na films prepared by the reactive direct current magnetron sputtering method

The fabrication of n- and p-type transparent oxide semiconductor films is critical in the production of transparent electrical and optoelectronic components on the p‒n junction, particularly the p-type, because the maximum of the valence band formed by the 2p orbitals of oxygen and their local (narrow) dispersions have formed deep levels, making difficult in doping of acceptor impurities in p-type oxide semiconductors. Among the p-type transparent oxide semiconductor films that have been studied so far, the p-type SnOx film which had outstanding electrical conductivity and optical transparency, is a good candidate for constructing a p‒n junction with another n-type semiconductor in homogeneous or heterogeneous form. In this paper, a Na-doped SnOx film was produced from Sn + 3 at% Na alloy target using the reactive sputtering process at a temperature of 200 0C. XRD, XPS, AFM, Hall, and UV-Visible techniques were used to evaluate the effect of sputtering duration on the structural and electro-optical properties of SnOx:Na films. The results of the survey showed that when the sputtering time increased from 7 minutes to 14 minutes, 21 minutes, and 35 minutes, the film thickness increased, resulting in an increase in the crystal size, a decrease in the grain boundary, and an increase in carrier mobility, all of which lead to a reduction in the film's resistivity. However, as the film thickness increased, the transmittance dropped and the optical bandgap shrinked.