Performance Enhancement of Organic Thin-Film Transistors by Low-Energy Argon Ion Beam Treatment of Gate Dielectric Surface

Abstract

In this paper, we report the effects of an argon (Ar) ion beam surface treatment of a SiO2 dielectric layer in organic thin-film transistors. We compared the electrical properties of pentacene deposited on a SiO2 layer after O2 plasma or Ar ion beam treatment and characterized the states of the surface of the dielectric by atomic force microscopy and X-ray photoelectron spectroscopy (XPS). For the sample that was subjected to O2 plasma cleaning, mobility increased significantly but the current on/off ratio was found to be very low. In contrast, the Ar-ion-beam-treated sample showed a very high current on/off ratio as well as a moderately improved mobility. The comparison of the XPS data taken from the dielectric surfaces after the two treatments revealed that the ratio between O–Si bonds and O–Si–O bonds was much higher in the O2-plasma-cleaned surface than in the Ar-ion-beam-treated surface. These results demonstrate that our surface treatment using an inert gas, Ar, enables an effective surface cleaning while keeping surface damage minimal and also marked improvements on electrical performances of organic thin-film transistors (OTFTs) were achieved as a consequence of improved surface conditions.