High-yield growth of semiconducting tungsten oxide nanowires

We characterized the growth, composition, and electrical properties of crystalline WO$_3$ nanowires grown using a catalyst-free chemical vapor deposition method. We showed that growing the wires in a mixture of methane and hydrogen dramatically increases the yield compared to growing the wires in argon carrier gas. The high yield makes simple nanowire `harvesting' schemes feasible. Additionally, we demonstrated that field-effect transistors can be produced using single WO$_3$ nanowires as the transistor channel. Devices made by using Ni as source and drain contacts are $n$-type and have good ON-currents and reasonable ON/OFF ratios. Scanning tunnelling spectroscopy gives a bandgap of about 2.2~eV.