Transparent and conductive Sm-doped SrSnO3 epitaxial films

Abstract Perovskite-structured (SmxSr1-x)SnO3 (SSSO) films with x = 0–0.15 were epitaxially grown on LaAlO3(001) substrates by pulsed laser deposition, and the microstructure, transport and optical properties were investigated in detail. X-ray diffraction results show that the lattice constants gradually decrease with the Sm content increasing. Atomic force microscopy images confirm that all the films possess a smooth surface with low surface roughness. X-ray photoelectron spectroscopy measurements prove the existence of Sm3+ state in the doped SSSO films. Hall-effect measurements show that the film at x = 0.06 has the lowest room-temperature resistivity of 5.91 mΩcm and the highest electron mobility of 14.8 cm2/Vs. Temperature-dependent resistivity curves were fitted and explained by weak localization effect and e--e- interactions at low temperatures for films at x = 0.04 to 0.10. Optical transparency of all the films is more than 70% in the wavelength range from 600 to 1800 nm, and the band gaps increase gradually from 4.27 to 4.60 eV with increasing Sm content to 0.06, which can be ascribed to Burstein-Moss effect. Furthermore, the insertion of pure SrSnO3 buffer layer between the substrate and the SSSO film considerably reduces the density of dislocations, thereby leading to the improved electrical transport property. All these results bring rare-earth element Sm a step closer to optoelectronic applications of all-perovskite transparent and conductive oxides.