Taylor, D. M.Gomes, Henrique L.Underhill, A. E.Edge, S.Clemenson, P. I.2015-06-262015-06-2619910022-3727AUT: HGO00803;http://hdl.handle.net/10400.1/6624Field effect devices have been formed in which the active layer is a thin film of poly(3-methylthiophene) grown electrochemically onto preformed source and drain electrodes. Although a field effect is present after electrochemical undoping, stable device characteristics with a high modulation ratio are obtained only after vacuum annealing at an elevated temperature, and only then if the devices are held in vacuo. The polymer is shown to be p type and the devices operate in accumulation only. The hole mobility in devices thermally annealed under vacuum is around 10 -3 cm 2 V -1 s -1. On exposure to ambient laboratory air, the device conductance increases by several orders of magnitude. This increase may be reversed by subjecting the device to a further high-temperature anneal under vacuum. Subsidiary experiments show that these effects are caused by the reversible doping of the polymer by gaseous oxygen.engjournal articlehttps://dx.doi.org/10.1088/0022-3727/24/11/019