Understanding the dependence of performance on the dielectric-semiconductor interface in pentacene-based organic field-effect transistors

The dependence of performance on the dielectric-semiconductor interface in pentacene-based organic field-effect transistors (OFETs) was investigated by modification of the substrate with octadecylsilane (OTS) compared with octadecyltrimethoxysilane (OTMS). The hole mobility of OFETs was enhanced from 0.43 cm²/V s to 0.72 cm²/V s when treating the substrate with OTMS versus OTS. However, the subsequent ammonia vapor did not lead to enhanced FET performance, which might be closely related to its negative influence on the pentacene growth. According to atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements, flat pentacene domains with larger grain sizes and less crystal boundaries were observed for the OTS treated surface, demonstrating higher crystallinity, which may play a positive role for the charge transport and thus accounts for the improved mobility.