Structural characterisation of high-mobility Cd₃As₂ films crystallised on SrTiO₃

Cd₃As₂ has long been known as a high-mobility semiconductor. The recent finding of a topological semimetal state in this compound has demanded growth of epitaxial films with high crystallinity and controlled thickness. Here we report the structural characterisation of Cd₃As₂ films grown on SrTiO₃ substrates by solid-phase epitaxy at high temperatures up to 600 °C by employing optimised capping layers and substrates. The As triangular lattice is epitaxially stacked on the Ti square lattice of the (001) SrTiO₃ substrate, producing (112)-oriented Cd₃As₂ films exhibiting high crystallinity with a rocking-curve width of 0.02° and a high electron mobility exceeding 30,000 cm²/Vs. The systematic characterisation of films annealed at various temperatures allowed us to identify two-step crystallisation processes in which out-of-plane and subsequently in-plane directions occur with increasing annealing temperature. Our findings on the high-temperature crystallisation process of Cd₃As₂ enable a unique approach for fabricating high-quality Cd₃As₂ films and elucidating quantum transport by back gating through the SrTiO₃ substrate.