Atomic Layer Deposition of Disordered p-Type SnO using a Heteroleptic Tin(II) Precursor: Influence of disorder on P-Channel SnO Thin-Film Transistor Characteristics

The readily scalable deposition of amorphous oxide semiconductor films is desirable for polymer-based flexible and large-area thin-film transistor technology. Here, the atomic layer deposition (ALD) of p-type SnO is demonstrated using a new heteroleptic tin(II) precursor. The films exhibit a disordered microstructure, due to the intercalation of fragments of the precursor ligands. Annealing induces crystallization of SnO, as volatile impurities are expelled from the film. Initial examination of bottom gate SnO thin-film transistors with SiO2 dielectric exhibit a maximum field-effect mobility of 1.9 cm2 V-1 s-1 and a minimum threshold voltage of 2 V, just before the onset of crystallization. Once capped with an alumina passivation layer, the devices have stable transfer characteristics over a period of two years, and a stable field effect mobility under negative bias stress of 1 MV.cm-1 for 2 hours at ambient. The disordered SnO semiconductor characteristics make it a candidate for polymer-based CMOS electronics, where a low thermal budget meets the requirements of polymeric substrates.