Effects of annealing temperature on the performance of the Schottky diode fabricated with TiO₂ sol-gel

Various conbinations of TiO₂ sol-gel were prepared to fabricate Schottky diodes. Pure TiO₂ sol-gel was spin-coated to the various substrates such as glass, silicon wafer, and cellulose. The sol-gel driven TiO₂ films were generated cracks all over the surface during the annealing process. To prevent cracks, polyethylene glycol (PEG) was added to TiO₂ sol-gel solution. TiO₂-PEG sol-gel was spin-coated to the substrate and heat treated at 100, 200, and 300°C for 1 h. The film thicknesses were 230, 190, and 129 nm for the sample heated at 100, 200, and 300°C, respectively, and no cracks were observed. The FTIR pesk at 3380 cm^-1 corresponds to -OH stretching mode and disappeared as the heating temperature increased. The characteristic peaks of PEG at 2875 and 1120 cm^-1 also disappeared as the heating temperature increased. The Schottky diodes comprised of Al/PEG-TiO₂/Au with various heat treatment were fabricated. The forward current was drastically increased as the annealing temperature increased. The plots of parabolic conduction curves based on Schottky conduction model, Poole-Frenkel conduction model, and space charge limitted conduction model show nonlinear relationship. These nonlinear relationship indicates that the conduction mechanism is not purely single conduction mechanism.