Improved Electrical Properties of Pentacene MIS Capacitor With OTS Modified Ta2O5 Dielectric

Ta₂O₅ hlms of 200 nm thick with and without octadecyltrichlorosilane (OTS) surface modihcation were prepared and used as gate dielectrics to fabricate pentacene metal-insulator-semiconductor (MIS) capacitors. The dielectric constants of Ta₂O₅ hlm and OTS-treated Ta₂O₅ hlm were determined to be 20.6 and 19.3 at 1 MHz, and both the hlms 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 hlm 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 modihcation 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× 10¹² cm-2eV^-1 to 9.6× 1010 cm^-2eV^-1. The results indicate that high-k Ta2O5 hlm with OTS modihcation would be a promising gate dielectric for pentacene thin-hlm transistors in low-end electronics.