This article investigates improving organic thin-film transistor (OTFT) characteristics by using an alignable high dielectric constant film to control the self-organization of pentacene molecules. The process, based on the growth of a pentacene film with high vacuum sublimation, is a method of self-organization that uses ion-beam (IB) bombardment of the HfO2/Al2O3 surface that serves as the gate dielectric layer. X-ray photoelectron spectroscopy indicates that the IB increases the structural anisotropy of the HfO2/Al2O3 film, and X-ray diffraction patterns show that increasing the anisotropy may lead to the self-organization of pentacene molecules in the first polarized monolayer. An effective mobility of 2.3x10(-3) cm(2) V-1 s(-1) was achieved, which is significantly different from the mobility in pentacene films that are not aligned. The proposed OTFT devices with an ultrathin HfO2 structure as the gate dielectric layer were operated at a gate voltage lower than 5 V.