September 2019: Section Oxides and Fluorides - IKZ develops Ba2ScNbO6 as new substrate crystal for novel functional layers and applications
Ba2ScNbO6 single crystal containing multicrystalline regions at the rim / Christo Guguschev © IKZ
Functional thin films are of strong contemporary interest in materials physics. Examples include La:BaSnO3, a semiconducting oxide exhibiting a very high electron mobility, LaInO3 as ionic gate oxide, BiScO3 as important constituent of a new class of high-temperature piezoelectrics and PbZrO3 as antiferroelectric material relevant to energy storage. These materials all feature a perovskite crystal structure with (pseudo-)cubic lattice parameters in slight excess of 4.1 Å, for which no substrate crystal was available. As a result, current studies are based on highly lattice-mismatched substrates leading to films with low structural quality and in case of electronic demonstration devices to insufficient performances.
This situation will change now, as IKZ and the Cornell University invented a novel bulk crystal growth technique tailored to the double-perovskite Ba2ScNbO6 . The growth conditions at about 2150°C are suitable to yield relatively large crystals (see Fig.) and (100)-oriented single-crystalline substrates with surface areas as large as 10 x 10 mm2. While the composition was chosen on a lattice parameter survey, the ability to grow the crystal from the melt was assessed by a thermo-chemical study. The achievement was published and a joint patent has been applied for. First La-doped BaSnO3 films grown on the new Ba2ScNbO6 substrates at the Cornell University already demonstrated the strong impact and benefit of using lattice-matched high-quality substrates .
 C. Guguschev et al., https://arxiv.org/ftp/arxiv/papers/1907/1907.02719.pdf
 H. Paik et al., “High mobility La-doped BaSnO3 thin film growth on lattice-matched Ba(Sc0.5Nb0.5)O3 (001) substrate by molecular-beam epitaxy”, poster at the 19th International Conference on Crystal Growth and Epitaxy (ICCGE-19/OMVPE-19), July 28 – August 2, 2019, Keystone, Colorado, USA.