Epitaxial and highly electrical conductive La₀.₅Sr₀.₅TiO₃films grown by pulsed laser deposition in vacuum

Abstract

The target material with nominal composition of La₀.₅Sr₀.₅TiO₃sintered in air is an insulator and not a single-phase compound. By pulsed laser ablation in vacuum at the multiphase La–Sr–Ti–O target, however, highly electrical conductive and epitaxial La₀.₅Sr₀.₅TiO₃films have been fabricated on LaAlO₃(001) substrates. Structural characterization using three-axis x-ray diffraction (θ–2θ scan, ω-scan rocking curve, and ϕ scan) reveals that the films have a pseudocubic structure and grow on the substrates with a parallel epitaxial relationship. Atomic force microscopy images show the films have quite smooth surface, for a film 200 nm thick, the roughness R[sub a] is about 0.31 nm over the 1 μmX1 μm area. Resistivity versus temperature measurements indicate that the films are metallic at 2–300 K and have resistivity of 64 μΩ cm at 300 K, which is about one order lower than that of the single-phase La₀.₅Sr₀.₅TiO₃bulk materials. After the same deposition procedure, epitaxial La₀.₅Sr₀.₅TiO₃films have also been grown on TiN buffered (001) Si substrates.