Transparent and conductive oxide films of the perovskite La_xSr_1−xSnO₃ (x ⩽ 0.15): epitaxial growth and application for transparent heterostructures

Abstract

Transparent and conductive oxide (TCO) films with a cubic perovskite structure, lanthanum-doped strontium stannate La x Sr 1− x SnO 3 ( x = 0–0.15) (LSSO), have been grown epitaxially on SrTiO 3 (0 0 1) substrates by the pulsed laser deposition method. The doping concentration and growth parameters were optimized based on the high-resolution x-ray diffraction and electric transport measurements. We found that the optimum doping level is around x = 0.07, and the epitaxial films can be grown at temperatures as low as 600 °C and in atmospheres compatible with many other perovskite oxide films. They are n-type TCO films, showing high optical transmittance in the visible range with a direct allowed band gap of 4.65 eV, and a weak metallic transport behaviour with a low resistivity of ∼4.0 mΩ cm within 10–300 K. Due to a very close lattice match with the ferroelectric Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) and multiferroic BiFeO 3 (BFO), all-perovskite LSSO(Pt)PZT(BFO)/LSSO capacitors and p-PZT(⩽20 nm)/n-LSSO [p-BFO (100 nm)/n-LSSO] p–n junctions have also been fabricated and characterized. The square polarization versus electric-field hysteresis loops, good rectifying characteristics, high optical transmittance, as well as the epitaxial growth exhibited by the heterostructures, strongly suggest that the LSSO films are potential candidates for use in transparent thin-film devices.