Capacitance–voltage and leakage-current characteristics of sol–gel-derived crystalline and amorphous SrTa2O6 thin films

Abstract

SrTa2O6 (STA) is a promising high-dielectric-constant (ε) material. In this study, STA thin films were fabricated using the sol–gel method. The capacitance–voltage and leakage-current characteristics of crystalline and amorphous STA thin-film capacitors were investigated. STA thin films crystallized at an annealing temperature of 800°C. Crystalline STA thin films exhibited a high ε of about 110, whereas amorphous STA thin films showed a much lower ε of about 26–41. However, amorphous STA thin films had a much more constant capacitance as a function of voltage. Of the amorphous thin films, the one annealed at 700°C had the highest ε of about 41, the lowest leakage current of 10−8A/cm2, and a very constant capacitance as a function of voltage with a quadratic voltage–capacitance coefficient (α) of 27ppm/V2. The crystalline STA thin film had a negative α that was independent of frequency, which suggests that dipolar relaxation occurs and is responsible for the large change in the capacitance. The amorphous thin films had a positive α that decreased with increasing frequency, which implies that electrode polarization occurs.