Growth-induced electron mobility enhancement at the LaAlO3/SrTiO3 interface

Fête, Alexandre; Cancellieri, Claudia; Li, Danfeng; Stornaiuolo, Daniela; Caviglia, Andrea D.; Gariglio, Stefano; Triscone, Jean‐Marc

doi:10.1063/1.4907676

Cited by 46 publications

(50 citation statements)

References 39 publications

(38 reference statements)

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“…At higher temperatures µ I decreases several orders of magnitude and reaches µ I = 7 cm 2 /Vs at room temperature. This trend is similar to what has previously been reported for LAO/STO heterostructures [31].…”

supporting

confidence: 92%

Insulator-to-Metal Transition at Oxide Interfaces Induced by WO₃ Overlayers

Mattoni

Baek²,

Manca

et al. 2017

ACS Appl. Mater. Interfaces

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Interfaces between complex oxides constitute a unique playground for 2D electron systems (2DES), where superconductivity and magnetism can arise from combinations of bulk insulators. The 2DES at the LaAlO 3 /SrTiO 3 interface is one of the most studied in this regard, and its origin is determined by both the presence of a polar field in LaAlO 3 and the insurgence of point defects, such as oxygen vacancies and intermixed cations. These defects usually reside in the conduction channel and are responsible for a decreased electronic mobility. In this work, we use an amorphous WO 3 overlayer to control the defect formation and obtain an increased electron mobility in WO 3 /LaAlO 3 /SrTiO 3 heterostructures. The studied system shows a sharp insulator-to-metal transition as a function of both LaAlO 3 and WO 3 layer thickness. Low-temperature magnetotransport reveals a strong magnetoresistance reaching 900% at 10 T and 1.5 K, the presence of multiple conduction channels with carrier mobility up to 80 000 cm 2 V −1 s −1 and an unusually high effective mass of 5.6 me. The amorphous character of the WO 3 overlayer makes this a versatile approach for defect control at oxide interfaces, which could be applied to other heterestrostures disregarding the constraints imposed by crystal symmetry.The formation of a two-dimensional electron system (2DES) at the interface between band insulators SrTiO 3 (STO) and LaAlO 3 (LAO) is among the most intriguing effects studied in oxide electronics [1]. Gate tunable superconductivity [2,3], strong spin-orbit coupling [4,5] and magnetism [6,7] are some of the many phenomena observed. The origin of this 2DES is a long standing question in the solid state community and recent results indicate that a consistent picture should take into account both the built-in polar field and the presence of point defects [8][9][10]. Among these, oxygen vacancies and cation off-stoichiometry in STO are capable of inducing a 2DES [11,12]. However, defects residing in the conductive channel are usually responsible for a decreased electronic mobility [13]. In order to promote high electron mobility, it is crucial to confine donor sites away from the conducting plane, without preventing the 2DES formation in the STO top layers. Previous attempts to control the defect concentration profile and thus enhance the mobility involved the use of crystalline insulating overlayers [14,15] [18,19]. A promising material to control defect formation is tungsten oxide WO 3 . The several possible oxidations states of tungsten make WO 3 particularly active in undergoing redox reactions. For this reason this material is often utilized in electrochemical applications and electrochromic devices [20][21][22]. Also, both crystalline and amorphous WO 3 can host vacancies and interstitial atoms, thus allowing cation accommodation and diffusion, with a tendency to form compounds such as tungsten bronzes [23,24]. Recent progress demonstrated the high-quality growth of WO 3 thin films on perovskite materials [25][26][27].In this work we co...

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supporting

confidence: 92%

Insulator-to-Metal Transition at Oxide Interfaces Induced by WO₃ Overlayers

Mattoni

Baek²,

Manca

et al. 2017

ACS Appl. Mater. Interfaces

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“…[69][70][71][72][73] For instance, reducing the growth temperature 74 or using special cappings of the LAO layer 75 allows mobilities of the order of 10 000 cm 2 /Vs to be reached at low temperature, these are associated with low carrier densities. The electronic structure and the control of superconductivity in such clean interfaces have yet to be determined.…”

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confidence: 99%

Research Update: Conductivity and beyond at the LaAlO3/SrTiO3 interface

2016

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In this review, we focus on the celebrated interface between two band insulators, LaAlO3 and SrTiO3, that was found to be conducting, superconducting, and to display a strong spin-orbit coupling. We discuss the formation of the 2-dimensional electron liquid at this interface, the particular electronic structure linked to the carrier confinement, the transport properties, and the signatures of magnetism. We then highlight distinctive characteristics of the superconducting regime, such as the electric field effect control of the carrier density, the unique tunability observed in this system, and the role of the electronic subband structure. Finally we compare the behavior of Tc versus 2D doping with the dome-like behavior of the 3D bulk superconductivity observed in doped SrTiO3. This comparison reveals surprising differences when the Tc behavior is analyzed in terms of the 3D carrier density for the interface and the bulk.

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“…[6][7][8][9][10][11][12][13] Motivated by interest in quantum phenomena and potential applications, multiple studies have specifically sought to improve the low-temperature electron mobility in LAO/STO interfaces. [13][14][15][16][17][18][19][20][21] In spite of more than a decade of research, the dominant scattering mechanism in LAO/STO interfaces, nonetheless, remains elusive.…”

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Universality of electron mobility in LaAlO3/SrTiO3 and bulk SrTiO3

Trier

Reich

Christensen

et al. 2017

Applied Physics Letters

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Metallic LaAlO3/SrTiO3 (LAO/STO) interfaces attract enormous attention, but the relationship between the electron mobility and the sheet electron density, ns, is poorly understood. Here, we derive a simple expression for the three-dimensional electron density near the interface, n3D, as a function of ns and find that the mobility for LAO/STO-based interfaces depends on n3D in the same way as it does for bulk doped STO. It is known that undoped bulk STO is strongly compensated with N≃5×1018 cm−3 background donors and acceptors. In intentionally doped bulk STO with a concentration of electrons n3D<N, background impurities determine the electron scattering. Thus, when n3D<N, it is natural to see in LAO/STO the same mobility as in the bulk. On the other hand, in the bulk samples with n3D>N, the mobility collapses because scattering happens on n3D intentionally introduced donors. For LAO/STO, the polar catastrophe which provides electrons is not supposed to provide an equal number of random donors and thus the mobility should be larger. The fact that the mobility is still the same implies that for the LAO/STO, the polar catastrophe model should be revisited.

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Growth-induced electron mobility enhancement at the LaAlO3/SrTiO3 interface

Cited by 46 publications

References 39 publications

Insulator-to-Metal Transition at Oxide Interfaces Induced by WO₃ Overlayers

Insulator-to-Metal Transition at Oxide Interfaces Induced by WO₃ Overlayers

Research Update: Conductivity and beyond at the LaAlO3/SrTiO3 interface

Universality of electron mobility in LaAlO3/SrTiO3 and bulk SrTiO3

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Growth-induced electron mobility enhancement at the LaAlO3/SrTiO3 interface

Cited by 46 publications

References 39 publications

Insulator-to-Metal Transition at Oxide Interfaces Induced by WO3 Overlayers

Insulator-to-Metal Transition at Oxide Interfaces Induced by WO3 Overlayers

Research Update: Conductivity and beyond at the LaAlO3/SrTiO3 interface

Universality of electron mobility in LaAlO3/SrTiO3 and bulk SrTiO3

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Product

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Insulator-to-Metal Transition at Oxide Interfaces Induced by WO₃ Overlayers

Insulator-to-Metal Transition at Oxide Interfaces Induced by WO₃ Overlayers