  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.
