Ta₂O₅-based high-K dielectric thin films from solution processed at low temperatures

Highlights: • Ta₂O₅–Al₂O₃–SiO₂ (Ta:Al:Si = 8:1:1 atomic ratio) and Ta₂O₅ films were processed from solutions. • The XRD-amorphous films, heated at or below 400 °C, are smooth (RMS < 0.5 nm). • The dielectric permittivity of the single- and mixed-oxide films heated at 400 °C is 27 and 22, respectively. • The current–voltage characteristics of the mixed-oxide films reveal the Poole–Frenkel behaviour. - Abstract: Ta₂O₅-based thin films were prepared by chemical solution deposition at temperatures not exceeding 400 °C. The aim of the work was to investigate the properties of high-K dielectric films of the ternary composition Ta₂O₅–Al₂O₃–SiO₂ with the Ta:Al:Si = 8:1:1 atomic ratio. Pure Ta₂O₅ samples were also prepared. All thin films were amorphous, and had smooth and flat surfaces with the average roughness of below 0.5 nm. The mixed oxide samples heated between 300 °C and 400 °C showed little difference in the dielectric permittivity with the values ranging from about 19 to 22. The Ta₂O₅ film heated at 400 °C exhibited the highest permittivity of about 27. The current–voltage measurements revealed considerably improved characteristics of the Ta₂O₅–Al₂O₃–SiO₂ samples within the investigated heating temperature range, with a significant overall decrease of the leakage currents in contrast to that of the pure Ta₂O₅ thin films