Low-Temperature-Processed High-Performance Pentacene OTFTs with Optimal Nd-Ti Oxynitride Mixture as Gate Dielectric

Abstract

When processed at a low temperature of 200 °C, organic thin-film transistors (OTFTs) with pentacene channel adopting high-k Neodymium-Titanium oxynitride mixtures (NdTiON) with various Ti contents as gate dielectrics are fabricated. The Ti content in the NdTiON is varied by co-sputtering a Ti target at 0 W, 10 W, 20 W and 30 W, respectively, while fixing the sputtering power of an Nd target at 45 W. High-performance OTFT is obtained for the 20 W-sputtered Ti, including a small threshold voltage of −0.71 V and high carrier mobility of 1.70 cm2/V·s. The mobility improvement for the optimal Ti content can be attributed to smoother dielectric surface and resultant larger overlying pentacene grains as reflected by Atomic Force Microscopy measurements. Moreover, this sample with the optimal Ti content shows much higher mobility than its counterpart processed at a higher temperature of 400 °C (0.8 cm2/V·s) because it has a thinner gate-dielectric/gate-electrode interlayer for stronger screening on the remote phonon scattering by the gate electrode. In addition, a high dielectric constant of around 10 is obtained for the NdTiON gate dielectric that contributes to a threshold voltage smaller than 1 V for the pentacene OTFT, implying the high potential of the Nd-Ti oxynitride in future high-performance organic devices.

Fused thiophene based materials for organic thin‐film transistors

“…[ 11 ] In parallel, alternate approaches towards improving the device performance have also been exploited, one of which is the tuning of charge transport via intentional chemical doping. [ 12 ] Among the various reported OSCs, fused‐acene‐based semiconductors such as pentacene, [ 13 ] oligothiophene, [ 14 ] thienothiophene (TT), [ 4n,15 ] dithienothiophene (DTT), [ 16 ] tetrathienoacene (TTA), [ 17 ] pentathienoacene (PTA), [ 18 ] and hexathienoacene (HTA) [ 18b,19 ] have received much attention because of their structural planarity and strong intermolecular S…S interaction/p–p interaction, which can enhance the dimensionality of the electronic structure, leading to superior carrier transfer efficiency. As a result, these units are often used in the OSCs for OTFT applications.…”