| AVS 66th International Symposium & Exhibition | |
| Complex Oxides: Fundamental Properties and Applications Focus Topic | Wednesday Sessions |
| Session OX+EM+MI+SS-WeM |
| Session: | Electronic and Magnetic Properties of Complex Oxide Surfaces and Interfaces |
| Presenter: | Friederike Wrobel, Argonne National Laboratory |
| Authors: | F. Wrobel, Argonne National Laboratory H. Hong, Argonne National Laboratory S. Cook, Argonne National Laboratory T.K. Andersen, Argonne National Laboratory D. Hong, Argonne National Laboratory C. Liu, Argonne National Laboratory A. Bhattacharya, Argonne National Laboratory D.D. Fong, Argonne National Laboratory |
| Correspondent: | Click to Email |
Epitaxial LaNiO3 (LNO) thin films and superlattices are known to be antiferromagnetic and weakly insulating for LNO thicknesses of 2 unit cells but paramagnetic and metallic for higher LNO thicknesses [1]. The quality of the single-crystal substrate surface, and in particular the chemical composition of the surface, is known to be a key factor governing the quality of the deposited thin film. For SrTiO3 (001) substrates, there are well-established preparation methods to ensure that the surface is TiO2-terminated and atomically smooth; the only features that appear with atomic force microscopy are the regular steps and terraces associated with crystal miscut. SrTiO3 is therefore often preferred as a substrate over other materials like (LaAlO3)0.3-(Sr2AlTaO6)0.7 (LSAT), whose surface composition is harder to control. Interestingly, for unknown reasons, the highest quality LaNiO3 thin films have been grown on mixed-terminated, untreated LSAT (001) substrates [2, 3]. At present, very few detailed studies have been conducted regarding the precise influence of the substrate on thin film growth behavior due to the need for an in-situ, atomic-scale characterization technique. Exploiting an in-situ, oxide molecular beam epitaxy (MBE) chamber at the Advanced Photon Source, we were able to monitor the deposition of thin films of LNO on LSAT (001) substrates with different surface compositions. Both non-resonant and resonant (Sr K-edge) X-ray scattering measurements were conducted at several points during the growth process. We observed the formation of atomically smooth, high-quality LNO films regardless of the initial substrate surface composition, suggesting that any excess, non-stoichiometric material on the initial LSAT substrate rises to the surface during deposition. With atomic layer-by-atomic layer MBE under the right conditions, we can therefore achieve self-healing growth behavior of complex oxides on top of mixed-terminated substrates. We will discuss details of the in-situ growth measurements and the methods used to determine the atomic and chemical structures.
1. Frano, A., et al., Orbital Control of Noncollinear Magnetic Order in Nickel Oxide Heterostructures. Physical Review Letters, 2013. 111(10): p. 106804.
2. Liu, C., et al., Counter-thermal flow of holes in high-mobility LaNiO3 thin films. Physical Review B, 2019. 99(4): p. 041114.
3. Wrobel, F., et al., Comparative study of LaNiO3/LaAlO3 heterostructures grown by pulsed laser deposition and oxide molecular beam epitaxy. Applied Physics Letters, 2017. 110(4): p. 041606.