High-mobility bottom-contact thin-film transistor based on anthracene oligomer

The mobility in top- and bottom-contact thin-film transistors (TFTs) based on 2,2-bianthryl (2A) was improved. The mobility of the top-contact 2A-TFT was improved from 0.25 to 1.0 cm2/Vs by octyltrichlorosilane (OTS) treatment of the SiO2 gate-insulator surface. Large grains and clear step structures corresponding to the molecular length of 2A were observed in the AFM image of a 2A film deposited on the OTS-treated SiO2. The bottom-contact 2A-TFT with typical source–drain (S–D) electrodes of Cr/Au showed a non-linear rise in the output characteristics due to the large injection barrier between the work function of Au and the HOMO level of 2A. The non-linear rise in the output characteristics was successfully improved by employing MoOx as the carrier injection layer for the S–D electrodes. Consequently, the mobility of the bottom-contact 2A-TFT with a MoOx/Au electrode was improved to 1.0 cm2/Vs, which is comparable to that in the top-contact 2A-TFT.