Hetero-epitaxial Growth of Cubic La(Sr)MnO3 on Hexagonal ZnO, in-plane orientations of La(Sr)MnO3 (001), (110), and (111) Phases

Abstract

Hexagonal ZnO was grown on a hexagonal (001) sapphire substrate. Then cubic La(Sr)MnO3 (LSMO) was grown on a ZnO underlayer by ion beam sputtering at various substrate temperatures to obtain double-layers of LSMO/ZnO and to investigate hetero-epitaxial orientation growth. Out-of-plane (001)-oriented ZnO was grown with an in-plane orientation of [10\bar{1}0](001)ZnO \parallel [11\bar{2}0](001)sapphire (B-mode). Three phases of LSMO with out-of-plane (001), (110), and (111) orientations were grown on (001) ZnO generally. However, each single phase of LSMO could be grown only by controlling the deposition conditions. We achieved the in-plane orientation growth of LSMO, [110](001)LSMO \parallel [10\bar{1}0](001)ZnO (B-mode), [1\bar{1}0](110)LSMO \parallel [10\bar{1}0](001)ZnO (A-mode), and [1\bar{1}0](111)LSMO \parallel [11\bar{2}0](001)ZnO (B-mode). The A-mode is defined as the mode in which both in-plane fundamental axes are parallel. The B-mode entails no parallel axes. The LSMO(001)- and (110)-grains have three equivalent in-plane domains, and the LSMO(111)-grain has a single domain. Lattice matching calculation can be used to partially interpret the orientation growth.