Crystal Structure Modification and Dielectric Properties of Sr- and La-Containing ABO Thin Films for High-Temperature Operational Film Capacitors.

In order to obtain thermally stable thin-film materials with high dielectric constant, ABO thin films (SrTaO, SrNbO, LaZrO, and LaTiO) containing Sr or La and their solid solutions were grown on Pt/Ti/SiO/Si substrates by RF sputtering and their crystal structures and dielectric properties were investigated. The SrTaO and LaTiO films exhibit highly oriented crystal structures. By contrast, the SrNbO and LaZrO films exhibit polycrystalline structures. The leakage properties of the Sr-containing films are lower and more stable in the high-temperature region (up to 300 °C) than those of the La-containing films. Among the investigated films, the SrTaO film grown at 500 °C and annealed at 900 °C shows the most stable dielectric constant with respect to temperature in the temperature range from room temperature to 300 °C. In addition, the SrTaO-(1-)LaTiO solid solutions exhibit enhanced dielectric properties at = 0.35. The dielectric constant is greater than 100, and its variation with temperature is less than 10%. The Sr-containing ABO ferroelectric thin films have potential applications as high-temperature film capacitors that can operate at temperatures as high as 300 °C.