Improved Electrical Properties of Pentacene MIS Capacitor With OTS Modified Ta2O5Dielectric

Abstract

Ta2O5 films of 200 nm thick with and without octadecyltrichlorosilane (OTS) surface modification were prepared and used as gate dielectrics to fabricate pentacene metal–insulator–semiconductor (MIS) capacitors. The dielectric constants of Ta2O5 film and OTS-treated Ta2O5 film were determined to be 20.6 and 19.3 at 1 MHz, and both the films exhibit good permittivity stability and low leakage characteristics with the bias voltage sweeping from −10 to 10 V. Atomic force microscopy and Hall measurements show that a pentacene polycrystalline film deposited on OTS-treated Ta2O5 has a high grain packing density with an improved grain contact, and thus a high hole mobility of 3.5 cm2/Vs. Capacitance–voltage and conductance–voltage analysis of pentacene MIS capacitors demonstrate that OTS modification induces a positive shift of flatband voltage from 3.1 to 3.8 V, and effectively minimizes the interface state density of pentacene/dielectric from $5.1\times 10^{12}$ cm $^{-2}$ eV $^{-1}$ to $9.6\times 10^{10}$ cm $^{-2}$ eV $^{-1}$ . The results indicate that high- ${k}$ Ta2O5 film with OTS modification would be a promising gate dielectric for pentacene thin-film transistors in low-end electronics.