LaAlO3 stoichiometry is key to electron liquid formation at LaAlO3/SrTiO3 interfaces

Warusawithana, Maitri; Richter, Christoph; Mundy, Julia A.; Roy, P.; Ludwig, Jonathan; Paetel, Stefan; Heeg, T.; Pawlicki, Alison A.; Kourkoutis, Lena F.; Zheng, Min; Lee, Minseong; Mulcahy, Brian; Zander, W.; Zhu, Ye; Schubert, J.; Eckstein, J. N.; Muller, David A.; Hellberg, C. Stephen; Mannhart, J.; Schlom, Darrell G.

doi:10.1038/ncomms3351

Cited by 210 publications

(216 citation statements)

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“…2b. Our reference LAO/STO heterostructure (0, 4) has RRR = 110, similarly to previous reports [12,29]. In the WO 3 /LAO/STO system we find higher values for decreasing thickness of the LAO interlayer.…”

supporting

confidence: 90%

“…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].…”

mentioning

confidence: 99%

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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: 90%

mentioning

confidence: 99%

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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“…Moreover, a systematic molecular beam epitaxy study showed that conducting interfaces are created only in the case of La deficient samples. In particular, as shown in Fig.3, a finite conductivity at the LaAlO 3 /SrTiO 3 interface is observed only for a La/Al ratio less than 0.97±0.03 [38].…”

Section: The Growth Of Laalo 3 /Srtio 3 Interfacesmentioning

confidence: 88%

Electronic Reconstruction at the Interface Between Band Insulating Oxides: The LaAlO3/SrTiO3 System

Salluzzo

2015

Oxide Thin Films, Multilayers, and Nanocomposites

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The conducting quasi-two dimensional electron system (q2DES) formed at the interface between LaAlO 3 and SrTiO 3 band insulators is confronting the condensed matter physics community with new paradigms. While the mechanism for the formation of the q2DES is debated, new conducting interfaces have been discovered paving the way to possible applications in electronics, spintronics and optoelectronics. This chapter is an overview of the research on the LAO/STO system, presenting some of the most important results obtained in the last decade to clarify the mechanism of formation of the q2DES at the oxide interfaces and its peculiar electronic properties as compared to semiconducting 2D-electron gas.

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“…A post-deposition annealing in a high oxygen pressure (0.1-1 bar) at 500 • C before cooling down to room temperature in the same atmosphere however allows an efficient suppression of these vacancies. Molecular beam epitaxy 27 and sputtering 28 have also been successfully employed for growing conducting LAO/STO interfaces. A particularly interesting outcome of the MBE approach has been the discovery of an unexpected dependence of the 2DEL formation on the stoichiometry of the LaAlO 3 layer.…”

Section: Realization Of Conducting Interfacesmentioning

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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LaAlO3 stoichiometry is key to electron liquid formation at LaAlO3/SrTiO3 interfaces

Cited by 210 publications

References 40 publications

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

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

Electronic Reconstruction at the Interface Between Band Insulating Oxides: The LaAlO3/SrTiO3 System

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

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LaAlO3 stoichiometry is key to electron liquid formation at LaAlO3/SrTiO3 interfaces

Cited by 210 publications

References 40 publications

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

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

Electronic Reconstruction at the Interface Between Band Insulating Oxides: The LaAlO3/SrTiO3 System

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

Contact Info

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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