Titania–silica hybrid films derived by a sol–gel process for organic field effect transistors

Titania–silica hybrid films with a thickness of 300 nm are fabricated by combining a sol–gel method with a spin-coating process from the acid-catalyzed organically modified silane solution of γ-glycidoxypropyltrimethoxysilane, methyltriethoxysilane and tetrapropylorthotitanate. The dielectric constants of the titania–silica hybrid films can be easily controlled by adjusting titanium content. Effects of titanium content and heat treatment temperature on the leakage current and surface roughness of the as-fabricated films are also optimized, thus, the hybrid film with smooth surface (R _q < 0.3 nm), high dielectric constant (k = 59.44) and low leakage current density (<1 nA cm⁻² at 5 V) is obtained and then used as the dielectric layer for the organic field effect transistors. Results indicate that the electrical properties of the organic field effect transistor fabricated by the titania–silica hybrid film as dielectric layer show an obvious improvement as compared with those of the organic field effect transistor fabricated by the thermally grown SiO₂ as dielectric layer, especially, in the improvement of the operating voltage (−2 V), field effect mobility (0.53 cm² V⁻¹s⁻¹) and sub-threshold swing (~130 mV/dec). It can be concluded that the titania–silica hybrid film shows a potential for the dielectric layer of the organic field effect transistors.