Effects of air-annealing on the electrical properties of p-type tin monoxide thin-film transistors

Abstract

We have investigated the effects of air-annealing on the electrical performance of the p-type tin oxide thin-film transistors (TFTs). The air-annealing of the tin oxide thin-film was made using a mini furnace at various temperatures. From the x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) data, it is demonstrated that the phase of tin oxide partially transforms from SnO to SnO2 with an air-annealing process, and it accelerates as the annealing temperature increases. The electrical performance of the p-type tin oxide TFT with a channel thickness of 25 nm exhibits much improved electrical performance when air-annealed at 230 degrees C for 1 h, but a decrease of the on-current is observed with an ambipolar operation in 260 and 290 degrees C air-annealed devices. Based on the XPS, XRD, and Hall measurement data, the reduced hole concentration inside the channel due to the recombination with electrons from SnO2 is believed to be the reason for the electrical performance improvement in 230 degrees C air-annealed p-type tin oxide TFTs, and a partial formation of n-type SnO2 channel is considered as the plausible reason for the ambipolar operation in tin oxide TFTs with high annealing temperatures. Our experimental results show that there is an optimum air-annealing temperature which can improve the electrical performance in p-type tin oxide TFTs.