Oxygen vacancy is known to play an important role for the physical properties in SrTiO3(STO)-based systems. On the surface, rich structural reconstructions had been reported owing to the oxygen vacancies, giving rise to metallic surface states and unusual surface phonon modes. More recently, an intriguing phenomenon of a huge superconducting transition temperature enhancement was discovered in a monolayer FeSe on STO substrate, where the surface reconstructed STO (SR-STO) may play a role. In this work, SR-STO substrates were prepared via thermal annealing in ultra-high vacuum followed by low energy electron diffraction analyses on surface structures. Thin Nb films with different thicknesses (
A variety of mechanisms are reported to play critical roles in contributing to the high carrier/electron mobility in oxide/SrTiO3(STO) heterostructures. By using La0.95Sr0.05TiO3(LSTO) epitaxially grown on different single crystal substrates (such as STO, GdScO3, LaAlO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, and CeO2buffered STO) as the model systems, the formation of a conducting substrate surface layer (CSSL) on STO substrate is shown at relatively low growth temperature and high oxygen pressure (725 °C, 5 × 10–4 Torr), which contributes to the enhanced conductivity of the LSTO/STO heterostructures. Different from the conventional oxygen vacancy model, this work reveals that the formation of the CSSL occurs when growing an oxide layer (LSTO in this case) on STO, while neither annealing nor the growth of an Au layer alone at the exact same growth condition generates the CSSL in STO. It demonstrates that the oxide layer actively pulls oxygen from STO substrate at given growth conditions, leading to the formation of the CSSL. The observations emphasize the oxygen transfer across film/substrate interface during the synthesis of oxide heterostructures playing a critical role in functional properties.
more » « less- NSF-PAR ID:
- 10446148
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Interfaces
- Volume:
- 9
- Issue:
- 11
- ISSN:
- 2196-7350
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The relationship between the sheet carrier concentration, $n_s$, of LaCrO$_3$(LCO)/SrTiO$_3$(STO) heterostructures and their structural properties has been investigated. Under low oxygen partial pressure, the STO substrate is reduced during growth as evidenced by a high $n_s$ of 10$^{16}$ cm$^{-2}$. By controlling the post-growth annealing conditions, heterostructures with $n_s$ of 10$^{13}$-10$^{16}$ cm$^{-2}$ are achieved. The atomic-scale structure of the samples are obtained using high-resolution synchrotron X-ray diffraction measurements. For heterostructures with $n_s$ at or below 3$\times 10^{13}$ cm$^{-2}$, polar distortions are present within the LCO layers and increase in magnitude with decreasing sheet carrier concentration. These distortions are absent for samples with $n_s$ on the order of 10$^{15}$-10$^{16}$ cm$^{-2}$ where interfacial carriers play a role in alleviating the polar discontinuity at the LCO/STO interface. These results suggest that interfacial charge carriers and polar distortions can act as complementary mechanisms to alleviate the polar discontinuity at polar/non-polar complex oxide interfaces.more » « less
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