Effects of annealing temperature, ambient humidity and temperature on dielectric properties of sol–gel-derived amorphous alumina thin film

Alumina is the great potential material for the high-energy-storage application. Annealing temperature, ambient humidity and temperature are crucial parameters for further investigations of alumina dielectrics. Highly dense and uniform amorphous alumina thin films were prepared by sol–gel and spin-coating technology. The effects of annealing temperature, relative ambient humidity and temperature on dielectric properties of amorphous alumina thin films were first investigated. The annealing temperature varied from 450 to 700 °C. The ambient humidities of 20, 40, 60 and 80% were chosen. The leakage current density of film annealed at 450 °C showed strong dependence on the ambient humidity. However, the effect of ambient humidity on leakage current density weakened as the annealing temperature rising. At the constant ambient humidity, films annealed at 450 and 500 °C showed lower leakage current densities than films annealed at 600 and 700 °C. The various annealing temperatures made little influence on dielectric loss but can enhance slightly the dielectric constant at 500 °C. The annealing temperature of 500 °C was reasonable and the resulting films exhibited stable conduction mechanism at various ambient temperatures. Moreover, the annealing temperature, ambient humidity and temperature did not make the remarkable influence on the breakdown strength.