Mott insulator to metal transition driven by oxygen incorporation in epitaxial LaTiO3 films

Zhang, T. T.; Gu, Chenyi; Mao, Zhiqiang; Chen, X. F.; Gu, Zheng‐Bin; Wang, P.; Nie, Yuefeng; Pan, Xiaoqing

doi:10.1063/1.5132568

Cited by 15 publications

(13 citation statements)

References 38 publications

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“…The 2DEG formed at the polar-metal LaTiO 3 + δ (LTO)/nonpolar-insulator STO interface is an alternative candidate 17 – 23 . Although LTO is an antiferromagnetic strongly correlated Mott insulator with a Ti 3+ (3 d 1 ) state in the native state, it usually transitions to a paramagnetic metal due to slight excess oxygen 19 , 20 or lattice distortion 21 . This metallic nature of LTO is desirable for the efficient transport of the spin current.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the LTO/STO interface is expected to be an ideal stage for efficient spin-charge conversion. We can incorporate a coherently grown single-crystal LTO layer into perovskite-oxide heterostructures due to their excellent lattice matching 20 . However, growing high-quality LTO is generally difficult because LTO easily changes to the La 2 Ti 2 O 7 phase 19 , 20 .…”

Section: Introductionmentioning

confidence: 99%

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Giant spin-to-charge conversion at an all-epitaxial single-crystal-oxide Rashba interface with a strongly correlated metal interlayer

et al. 2022

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The two-dimensional electron gas (2DEG) formed at interfaces between SrTiO3 (STO) and other oxide insulating layers is promising for use in efficient spin-charge conversion due to the large Rashba spin-orbit interaction (RSOI). However, these insulating layers on STO prevent the propagation of a spin current injected from an adjacent ferromagnetic layer. Moreover, the mechanism of the spin-current flow in these insulating layers is still unexplored. Here, using a strongly correlated polar-metal LaTiO3+δ (LTO) interlayer and the 2DEG formed at the LTO/STO interface in an all-epitaxial heterostructure, we demonstrate giant spin-to-charge current conversion efficiencies, up to ~190 nm, using spin-pumping ferromagnetic-resonance voltage measurements. This value is the highest among those reported for all materials, including spin Hall systems. Our results suggest that the strong on-site Coulomb repulsion in LTO and the giant RSOI of LTO/STO may be the key to efficient spin-charge conversion with suppressed spin-flip scattering. Our findings highlight the hidden inherent possibilities of oxide interfaces for spin-orbitronics applications.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Giant spin-to-charge conversion at an all-epitaxial single-crystal-oxide Rashba interface with a strongly correlated metal interlayer

et al. 2022

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“…Although conduction mechanisms based on polar catastrophe and OV in LAO/STO systems are well studied, [5,15,20,21,32] the origin of OV is less clear. [6,8,10,14,19,20,33] The generation of OV is often believed to be due to the low oxygen growth pressure at high growth temperatures. [19][20][21] However, the oxygen transfer between the oxide substrate and oxide layer could be linked to OV origin.…”

Section: Introductionmentioning

confidence: 99%

The Role of Oxygen Transfer in Oxide Heterostructures on Functional Properties

Corey

Han

Kang

et al. 2022

Adv Materials Inter

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achieved by interfacing two insulting oxides have attracted great attention in the past decade. [3][4][5][6][7][8][9][10] Different conduction mechanisms including polar catastrophe (interface), [5,10,11] strain, [12][13][14] intermixing (doping), [3,8,[15][16][17] and oxygen vacancy (defect) [18][19][20][21] have been proposed to explain such phenomenon. For example, carriers at the substrate-film interface (interface), bulk part of the film (film) and the surface layer of the substrate near the substratefilm interface (substrate surface layer) can all contribute to the effective conductivity of the samples. Polar catastrophe is a wellestablished model to explain the high conductivity at the interface between LaAlO 3 and SrTiO 3 (LAO/STO). [5,11,20] High mobility has also been reported when LaTiO 3 (LTO) and La 1-x Sr x TiO 3 (LSTO) are grown on SrTiO 3 (STO) [8,14,16,22] and KTaO 3 (KTO). [6] LTO is a polar perovskite like LAO, and as such, polar catastrophe mechanisms of this system are assumed to follow similarly to that of LAO/STO heterostructures. [5,11,20] However, unlike LAO, which is a band insulator, LTO is a Mott insulator that shows an insulator-metal transition when doped with Sr 2+ in polycrystalline bulk and epitaxial thin films. This allows the 3d 1 configuration to approach 3d 0 and may also result in the observed metallic behavior as reported in LSTO films on substrates such as (LaAlO 3 ) 0.3 (Sr 2 AlTaO 6 ) 0.7 (LSAT). [17,23] In addition, defects such as oxygen vacancy (OV) in the STO substrate are another factor which could affect the electric conductivity in STO-based heterostructures. The formation of OV in STO substrate is directly controlled by growth temperature and oxygen pressure as reported in different oxide/STO heterostructures. [5,15,18,20,21,[23][24][25][26][27][28] Enhanced conductivity is observed for these heterostructures grown (and STO single crystals annealed) in temperatures greater than 750 °C, at oxygen pressures lower than 10 -5 Torr or a combination of both. [29] For example, OVs can be introduced by reducing the STO substrate with pre-substrate annealing (PSA) at 750 °C and 10 -6 Torr. [28] Spinelli, et al. reported highly conductive STO crystals annealed at 10 -9 Torr and 700 °C. [29] Schneider et al. found substantial oxygen transfer from STO substrates to oxide films while studying the diffusion of isotope 18 O at the conditions of 750 °C and 1 × 10 -8 Torr. [19] Edmondson et al. observed STO substrate reduction at 10 -10 ~ 10 -7 Torr and 700 °C. [20] Therefore, the formation of OV near the STO surface or the diffusion of oxygen out A variety of mechanisms are reported to play critical roles in contributing to the high carrier/electron mobility in oxide/SrTiO 3 (STO) heterostructures. By using La 0.95 Sr 0.05 TiO 3 (LSTO) epitaxially grown on different single crystal substrates (such as STO, GdScO 3 , LaAlO 3 , (LaAlO 3 ) 0.3 (Sr 2 AlTaO 6 ) 0.7 , and CeO 2 buffered STO) as the model systems, the formation of a conducting substrate surface layer (CSSL) on STO substr...

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“…SrTiO 3 (STO)-based epitaxial heterostructures host a variety of exotic phenomena and have attracted considerable attention over the past decades. − As high electron mobility is essential for the applications in electronic devices, numerous methods have been reported to create conductive STO thin films or STO-based heterostructures and enhance the electron mobility, including strain engineering, − complex interfacial effects, − and optimization of the density and types of dopants. − In most cases, the cation dopants and carrier concentration are fixed and not tunable after growth. In contrast, the oxygen-vacancy-induced conductivity is expected to have greater tunability since oxygen vacancies are rather mobile and can be modulated after growth easily.…”

Section: Introductionmentioning

confidence: 99%

Rewritable High-Mobility Electrons in Oxide Heterostructure of Layered Perovskite/Perovskite

Chen

Zhang

Yang

et al. 2021

ACS Appl. Mater. Interfaces

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Perovskite oxide SrTiO3 can be electron-doped and exhibits high mobility by introducing oxygen vacancies or dopants such as Nb or La. A reversible after-growth tuning of high mobility carriers in SrTiO3 is highly desired for the applications in high-speed electronic devices. Here, we report the observation of tunable high-mobility electrons in layered perovskite/perovskite (Sr n+1Ti n O3n+1/SrTiO3) heterostructure. By use of Sr n+1Ti n O3n+1 as the oxygen diffusion barrier, the oxygen vacancy concentration near the interface can be reversibly engineered by high-temperature annealing or infrared laser heating. Because of the identical elemental compositions (Sr, Ti, and O) throughout the whole heterostructure, interfacial ionic intermixing is absent, giving rise to an extremely high mobility (exceeding 55000 cm2 V–1 s–1 at 2 K) in this type of oxide heterostructure. This layered perovskite/perovskite heterostructure provides a promising platform for reconfigurable high-speed electronic devices.

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Mott insulator to metal transition driven by oxygen incorporation in epitaxial LaTiO3 films

Cited by 15 publications

References 38 publications

Giant spin-to-charge conversion at an all-epitaxial single-crystal-oxide Rashba interface with a strongly correlated metal interlayer

Giant spin-to-charge conversion at an all-epitaxial single-crystal-oxide Rashba interface with a strongly correlated metal interlayer

The Role of Oxygen Transfer in Oxide Heterostructures on Functional Properties

Rewritable High-Mobility Electrons in Oxide Heterostructure of Layered Perovskite/Perovskite

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