Growth and characterization of heteroepitaxial La-substituted BaSnO$_3$ films on SrTiO$_3$ (001) and SmScO$_3$ (110) substrates

TL;DR

This study successfully grew and characterized La-substituted BaSnO$_3$ thin films on different substrates, revealing high crystallinity, stoichiometry, and degenerate semiconducting behavior with substrate-dependent electrical properties.

Contribution

It demonstrates the heteroepitaxial growth of La-doped BaSnO$_3$ films with high quality and explores how substrate choice affects their electrical performance.

Findings

Films are highly crystalline with smooth surfaces.

La content exceeds bulk solubility limit.

Electrical properties vary with substrate, showing better performance on SmScO$_3$.

Abstract

Heteroepitaxial growth of BaSnO$_3$ (BSO) and Ba$_{1-x}$La$_x$SnO$_3$ (x = 7 %) (LBSO) thin films on different perovskite single crystal (SrTiO$_3$ (001) and SmScO$_3$ (110)) substrates has been achieved by Pulsed Laser Deposition (PLD) under optimized deposition conditions. X-ray diffraction measurements indicate that the films on either of these substrates are relaxed due to the large mismatch and present a high degree of crystallinity with narrow rocking curves and smooth surface morphology while analytical quantification by proton induced x-ray emission (PIXE) confirms the stoichiometric La transfer from a polyphasic target, producing films with La contents above the bulk solubility limit. The films show degenerate semiconducting behavior on both substrates, with the observed room temperature resistivities, Hall mobilities and carrier concentrations of 4.4 $m \Omega cm$, 10.11 $cm^2 V^{-1} s^{-1}$, and 1.38 $\cdot 10^{20} cm^{-3}$ on SmScO$_3$ and 7.8 $m \Omega cm$, 5.8 $cm^2 V^{-1} s^{-1}$, and 1.36 $\cdot 10^{20} cm^{-3}$ on SrTiO$_3$ ruling out any extrinsic contribution from the substrate. The superior electrical properties observed on the SmScO3 substrate are attributed to reduction in dislocation density from the lower lattice mismatch.