Formation of cerium oxide film via post-sputter oxidation of cerium in nitrogen/oxygen/nitrogen ambient

Abstract

Bulk cerium film deposited on silicon was transformed into cerium oxide (CeO2) by post-sputter oxidation at 400, 600, 800, and 1000 °C in nitrogen/oxygen/nitrogen ambient. The CeO2 films which were in oxygen deficient at 400°C was transformed progressively to metastable Ce3+/Ce4+ at 600°C and oxygen rich CeO2 at 800 and 1000°C. Dispersion behaviors of the CeO2 films were investigated in terms of refractive index, extinction coefficient, and complex dielectric functions. Owing to a reduction of oxygen vacancies, a decrease in the electron density was attained, altering the dispersion behaviors. Excess electrons present in the film oxidised at 1000°C encouraged the formation of cerium silicate interfacial layer at the CeO2/Si interface. A reduction in dielectric function value was obtained yet the loss tangent was the lowest. Besides, the largest band gap was also obtained at 1000°C, contributing to the lowest leakage current density in the film. Structural, morphological, and optical characteristics of the investigated films were studied in correlation with the aforementioned findings.