Characteristics of Pentacene Organic Field-Effect Transistors with Self-Assembled-Monolayer-Treated HfO2 Gate Oxide

In this study, the dependence of the crystal structure and dislocation distribution of pentacene on high-dielectric-constant hafnium oxide (HfO2) after surface modification is investigated. In addition to the analysis of pentacene layer such as crystal structure and grain size, the electrical characteristics of devices depending on surface modification are also investigated. As a surface modification of the HfO2 gate oxide, octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) are used. OTS monolayers with hydrophobic functional groups react stably on HfO2 film. They play an important role in decreasing the surface energy of HfO2 film to below about 45 mN/m. In addition, they significantly affect the crystal structure, dislocation distribution, and alignment of pentacene. As a result of OTS SAMs treatment, the mobility of pentacene devices was improved by the presence of a single thin-film phase that led to through the high ordering of pentacene molecules alignment and the lower scattering at the surface and dislocation. (C) 2009 The Japan Society of Applied Physics