model system

Various oxide interfaces with composition RAlO₃/SrTiO₃ (R = La, Pr, Nd) can produce a two-dimensional electron gas (2DEG). Crystallization from amorphous precursors, termed solid phase epitaxy (SPE), is an approach for synthesizing these interfaces that complements vapor-phase epitaxy techniques. Atomic layer deposition (ALD) is a promising route for forming the amorphous films because it allows oxide interfaces to be created in non-planar geometries. SPE can be used with patterned substrates to grow epitaxial thin films in complex geometries, which may enable the creation of 2DEG beyond planar geometries.
The creation of PrAlO₃ thin films via SPE has required developing new ALD procedures, understanding crystallization kinetics, and probing the microstructure and interface structures of the crystallized thin films. Nearly stoichiometric amorphous PrAlO₃ thin films were grown via ALD at 300 °C using tris(isopropylcyclopentadienyl)praseodymium, AlMe₃, and water with a growth rate of 2.0 Å/cycle on TiO₂-terminated STO (001) substrates. The as-deposited amorphous PrAlO₃ crystallized via SPE to form an epitaxial layer on STO upon annealing at 800 °C for 3h. Our work provides new opportunities to form polar/nonpolar oxide interfaces, and the accompanying 2DEG in novel geometries.