Hydrothermal growth of BaSnO3 single crystals for wide bandgap applications

Abstract

A method for the synthesis of single crystals of BaSnO3 is reported. The growth employs a hydrothermal process using simple Ba(OH)2 and SnO2 powders in water at 650 °C and 140 MPa, with 5 M CsOH mineralizer in welded inert metal liners. Solubility studies indicate that the crystals have positive solubility coefficients that increase with temperature and mineralizer concentration in the growth regimes investigated. The tetravalent tin ions are somewhat aggressive toward the inert metal liners, especially silver and gold, requiring platinum liners for longer term growth runs. The (1 1 0) and (1 0 0) faces are commonly observed on the as-grown crystals. The crystals are thermally and chemically stable and can be readily polished as substrates for subsequent epitaxial growth. Crystals that are n-doped (La:BaSnO3) can be grown by the addition of the desired amount of La2O3 to the initial feedstock. The band gap for this hydrothermally-grown BaSnO3 was measured using the Tauc plot method to be 2.94 eV, with approximately 0.3 eV shift to higher energy upon n-doping.