Amorphous Tin Oxide Applied to Solution Processed Thin-Film Transistors

The limited choice of materials for large area electronics limits the expansion of applications. Polycrystalline silicon (poly-Si) and indium gallium zinc oxide (IGZO) lead to thin-film transistors (TFTs) with high field-effect mobilities (>10 cm(2)/Vs) and high current ON/OFF ratios (I(On)/I(Off) > ~10(7)). But they both require vacuum processing that needs high investments and maintenance costs. Also, IGZO is prone to the scarcity and price of Ga and In. Other oxide semiconductors require the use of at least two cations (commonly chosen among Ga, Sn, Zn, and In) in order to obtain the amorphous phase. To solve these problems, we demonstrated an amorphous oxide material made using one earth-abundant metal: amorphous tin oxide (a-SnO(x)). Through XPS, AFM, optical analysis, and Hall effect, we determined that a-SnO(x) is a transparent n-type oxide semiconductor, where the SnO(2) phase is predominant over the SnO phase. Used as the active material in TFTs having a bottom-gate, top-contact structure, a high field-effect mobility of ~100 cm(2)/Vs and an I(On)/I(Off) ratio of ~10(8) were achieved. The stability under 1 h of negative positive gate bias stress revealed a Vth shift smaller than 1 V.