Carrier injection property of C₆₀ thin film transistor via displacement current measurement

Carrier injection into a C₆₀ thin film has been studied from characteristics of a field effect transistor and a displacement current measurement (DCM) using three kinds of metals, Mg, Ag, and Au. The Mg sample shows a highest field effect mobility of 0.62 cm²/Vs and a lowest threshold voltage of 6 V among the samples. A carrier injection and the accumulation are confirmed in the DCM curves by sweeping voltage applied on the back gate. The electron number and the density injected from the electrodes are estimated from the integration of the DCM curves. However, only the curve of the Mg sample shows a two-stage transition in the DCM curves. It could be due to a diffusion of Mg atoms into the C₆₀ layer and a transition of releasing electrons from the donor level could be observed at lower voltage region.