The effect of surface treatment of bottom contact organic thin film transistor

Abstract

A bottom contact organic thin film transistor (OTFT) is fabricated with an organic double-layered gate insulator (Cl) and pentacene. Poly(methyl methacrylate) (PMMA) and 2-mercapto 5-nitrobenzimidazole (MNB) layers are deposited on the gate insulator and source/drain gold (S/D. Au) electrode before depositing pentacene to investigate the device properties. The sequence of surface treatment significantly affects the device performance. The ultra-thin PMMA (less than 5 nm) was deposited on the organic gate insulator and S/D metal by the spin coating method, which caused no deterioration of the on-state current (I(on)), although a bottom contact structure was exploited. The lack of increase in the contact resistance (R(c)) may be due to the difference in wettability between PMMA/Au and PMMA/organic Cl. As a result, the devices treated with PMMA -˃ MNB showed much better I(on) behavior than those fabricated with MNB -˃ PMMA. We report on the difference in the physical and electrical performances associated with the surface treatment sequence.