Interface effect in pentacene field-effect transistors from high energy proton beam irradiation

We report the effect of irradiation using 10 MeV high energy proton beams on pentacene organic field-effect transistors (OFETs). The electrical characteristics of the pentacene OFETs were measured before and after proton beam irradiation with fluence (dose) conditions of 10¹², 10¹³, and 10¹⁴ cm^-2. After proton beam irradiation with fluences of 10¹² or 10¹³ cm^-2, the threshold voltage of the OFET devices shifted to the positive gate voltage direction with an increase in the current level and mobility. In contrast, for a high proton beam fluence condition of 10¹⁴ cm^-2, the threshold voltage shifted to the negative gate voltage direction with a decrease in the current level and mobility. It is evident from the electrical characteristics of the pentacene OFETs treated with a self-assembled monolayer that these experimental observations can be attributed to the trapped charges in the dielectric layer and pentacene/SiO₂ interface. Our study will enhance the understanding of the influence of high energy particles on organic field-effect transistors.