Effects of yttrium additions on the microstructure and charge transport properties of indium tin oxide semiconductors

The effects of yttrium (Y) additions (x=0, 0.05, 0.1, and 0.2) on the microstructure, chemical structure, and electrical properties of YxInSnOy (YITO) thin films, prepared using a sol-gel process were examined. The transmission electron microscopy (TEM) observations showed that the undoped InSnO (ITO) film consisted of an amorphous structure with local crystalline domains on the film surface, whereas the Y additions (x=0.05, 0.1, and 0.2) to ITO suppressed the formation of the crystalline phase. X-ray photoelectron spectroscopy (XPS) analysis showed that the Y content decreased the concentration of oxygen vacancies owing to the strong incorporation of Y with oxygen. As a result of the Y incorporation, the carrier concentration of ITO films decreased. The saturation mobility (μsat), the on-off ratios (Ion/off), and the sub-threshold swing (S.S) of YITO films were 1.1 cm2 V−1 s−1, ~106, and ~0.5 V decade−1, respectively, which are comparable with 1.7 cm2 V−1 s−1, ~105, and ~1.17 V decade−1 of ITO film. Additionally, the initial threshold voltage (VTH) was positive shift with increased of Y addition and VTH shift (ΔVTH) under the positive bias stress (PBS) results decreased by Y addition.