In this study, magnesium (Mg)-doped zinc tin oxide (ZTO) films were deposited by radio frequency (RF) magnetron sputtering. The Mg was selected as an electron suppressor for the ZTO films. X-ray diffraction (XRD) was carried out to observe the crystallinity of the films. The Mg-doping effects on the elemental properties of the films were investigated by X-ray photoelectron spectroscopy (XPS). The optical properties, such as transmittance, optical band gap, Urbach energy, and refractive index, were compared as a function of Mg content. Bottom-gate transparent thin-film transistors (TTFTs) were fabricated on l\P Si wafers. The turn-off voltage, threshold voltage, and mobility variation as a function of Mg content were studied. (C) 2013 Elsevier B.V. All rights reserved.