Vapor-phase deposition of the fluorinated copolymer gate insulator for the p-type organic thin-film transistor

Abstract

A copolymer-based gate insulator was synthesized from 1,3,5-trivinyl-1,3,5-trimethyl cyclotrisiloxane (V3D3) and 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate (PFDMA) via initiated chemical vapor deposition. The synthesis of the random copolymer of poly(V3D3-co-PFDMA) was confirmed by Fourier transform infrared, X-ray photoelectron spectroscopy, and water contact angle analysis. No phase segregation and pinhole formation were observed in the atomic force microscopy images of the copolymer film. The ultra-thin copolymer film showed an extremely low leakage current density (J < 10−9A/cm2 in the range of ±2MV/cm) even with a 70nm thickness. Pentacene organic thin-film transistors (OTFTs) were fabricated with the copolymer gate insulator and showed excellent operational stability. An up to 95% initial drain current was maintained, and a negligible shift in threshold voltage (VT) was observed even after applying a constant gate bias stress of −12V and a corresponding electric field of 1.7MV/cm to the OTFT for 3ks.