Effects of the Surface Treatment with Monolayers of Twisted Biaryls on the Efficiency of Pentacene Thin-Film Transistors

Abstract

A pentacene thin-film transistor (TFT) was fabricated on a SiO2 gate insulator modified with twisted biaryls. The biaryl monolayer, in particular a binaphthyl (BN) monolayer, is amorphous surface where the naphthalene rings are randomly oriented with no lateral order because of their rigid, twisted, and asymmetric shape. When the BN monolayer was used for the surface treatment of SiO2, large grains were obtained in the early stages of the pentacene crystal growth. The pentacene TFT had a field effect mobility (mu) in excess of 0.4 cm(2)/Vs and an on/off ratio greater than 10(5). The surface treatment improved the mobility of the pentacene TFT by a factor of 50% compared with non-treated devices. The morphology of the semiconductor layer was investigated using atomic force microscopy (AFM) and X-ray diffraction (XRD).