Polycrystalline zinc oxide (ZnO) thin-film transistors with a Ta 2 O 5 high-k gate dielectric layer are fabricated by radio-frequency magnetron sputtering at room temperature. Under the optimal deposition conditions, the devices show saturation mobility values over 50 cm 2 /Vs, an ON/OFF ratio of > 10 5 , and a subthreshold voltage swing of 0.29 V/decade at a low operating voltage of 4 V. This is, to the best of our knowledge, one of the highest field-effect mobility values achieved in ZnO-based thin-film transistors by room-temperature sputtering. The stability of the devices is also examined and the sensitive dependence of the carrier mobility on the deposition conditions is discussed.

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Nanometer-scale self-switching devices (SSDs) fabricated in polycrystalline zinc oxide have been demonstrated up to at least 51.5 MHz, functioning as rectifiers to generate DC voltage. The SSDs require only a single nanolithography step and hence are of interest to low-cost printed electronics. The devices showed stable performance within the frequency range tested. The as-fabricated devices possessed strongly nonlinear current-voltage characteristics, resembling those of conventional diodes. After coating the devices with poly methyl methacrylate and poly vinylidene fluoride to enhance the electric field coupling, the nonlinear behavior was maintained while the device current increased dramatically.

The cutoff frequency and current from an organic thin-film transistor (OTFT) is strongly dependent on the length and to some extent the uniformity of the transistor channel. Reducing the channel length can improve the OTFT performance by increasing the current and frequency. Picosecond laser ablation of printed Ag electrodes, compatible with roll-to-roll fabrication has been investigated. The ablation threshold was found to be similar for the laser wavelengths tested: 515 nm and 1030 nm. Short transistor channels could be opened both after light annealing at 70 o C and after annealing at 140 o C. The channels in the lightly cured films had significantly less scale formation which critical for avoiding shunts in the device. By moving from bottom electrodes fully defined by printing to bottom electrodes where the transistor channel is opened by laser, the channel length could be reduced from 40 µm to less than 5 µm.