A cross-linked poly(methyl methacrylate) gate dielectric by ion-beam irradiation for organic thin-film transistors

The electrical characteristics of pentacene organic thin-film transistors (OTFTs) using cross-linked poly(methyl methacrylate) (PMMA) as the gate dielectric are reported. Ultra-thin films of cross-linked PMMA could be obtained by spin-coating and subsequent irradiation using a 1.515 MeV 4He+ ion beam. The resulting film, with a thickness of 33 nm, possessed a low leakage current density of about 10−6 A cm−2 for fields up to 2 MV cm−1. OTFTs incorporating the cross-linked dielectric operated at relatively low voltages, <10 V, and exhibited a mobility of 1.1 cm2 V−1 s−1, a threshold voltage of −1 V, a sub-threshold slope of 220 mV per decade and an on/off current ratio of 1.0 × 106.