Single crystal Gd₂O₃ epitaxially on GaAs(111)A

Gd₂O₃ films 2 and 6 nm thick, electron-beam evaporated from a compact powder target, were deposited on freshly molecular beam epitaxy (MBE) grown epi-GaAs(111)A in a multi-chamber MBE system. The oxide films are epitaxial with the underlying GaAs, as studied by in situ reflective high energy electron diffraction and high-resolution X-ray diffraction using synchrotron radiation. The films undergo a structure phase transformation from hexagonal to monoclinic when the film thickness increases from 2 to 6 nm; the 2 nm oxide has H-Gd₂O₃(0001)[100]‖GaAs(111)[4] orientation relationship and the 6 nm film follows M-Gd₂O₃(01)[102]‖GaAs(111)<4> with 3 rotational variants anchored by the 3-fold symmetric substrate. Here, H and M denote the hexagonal and monoclinic phases, respectively.