Abstract
The interfaces of complex oxide heterostructures exhibit intriguing phenomena not observed in their constituent materials. The oxide thin-film growth of such heterostructures has been successfully controlled with unit-cell precision; however, atomic-scale understandings of oxide thin-film surfaces and interfaces have remained insufficient. We examined, with atomic precision, the surface and electronic structures of oxide thin films and their growth processes using low-temperature scanning tunneling microscopy. Our results reveal that oxide thin-film surface structures are complicated in contrast to the general perception and that atomically ordered surfaces can be achieved with careful attention to the surface preparation. Such atomically ordered oxide thin-film surfaces offer great opportunities not only for investigating the microscopic origins of interfacial phenomena but also for exploring new surface phenomena and for studying the electronic states of complex oxides that are inaccessible using bulk samples.
Highlights
Surfaces and interfaces are known to play crucial roles in materials science
To investigate atomic-scale surface structures and electronic states of oxide thin films, we first constructed a low-temperature STM integrated with a pulsed laser deposition (PLD) (STM–PLD system)
After cooling the sample to room temperature, we transfer the samples to the STM head under ultrahigh vacuum (UHV) conditions
Summary
Surfaces and interfaces are known to play crucial roles in materials science. For instance, electronic devices underpinning modern technologies greatly rely on two-dimensional (2D) electron gases formed at the interface of semiconductor heterostructures [1]. Because of the broken inversion symmetry at surfaces and interfaces, interesting physical phenomena are widely observed such as spontaneous spin polarization in strong spin– orbit coupling systems [3]. Since the discovery of metallic behavior with high mobility at the interface of LAO/STO [6], physical properties including superconductivity [7] and magnetism [8], which are unexpected from the bulk properties, have been reported. These results suggest that atomic-precision control of interface structures would open up a path for the exploration of new functional properties at surfaces and interfaces. Several challenges that remain to be overcome and future perspectives are reviewed
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