Localization of two-dimensional electron gas in LaAlO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>/SrTiO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>heterostructures

Hernández, Tony; Bark, Chung Wung; Felker, D. A.; Eom, C. B.; Rzchowski, M. S.

doi:10.1103/physrevb.85.161407

Cited by 39 publications

(42 citation statements)

References 34 publications

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“…We should also note that this loss of the 2DEG properly highlights the fact that oxygen vacancies, which can possibly be formed during the growth, 23 seem not to be the relevant origin of the metallicity in this study. Looking at Figures 2(b) and 2(c), however, raises the question: why is this loss also observed for ex situ samples, albeit at higher STO critical thickness?…”

Section: -3mentioning

confidence: 99%

“…Efforts have been made towards realizing such interfaces between LAO and artificially grown STO films and conducting LAO/STO interfaces grown on other substrates have been achieved. [21][22][23][24] However, the metallic behavior was no longer maintained in the low temperature range and localization effects were observed. 23 The main obstacle remains to be preserving both the metallicity down to the lowest temperature and the two-dimensional nature of the electron gases by using proper oxygen deposition conditions.…”

mentioning

confidence: 99%

“…[21][22][23][24] However, the metallic behavior was no longer maintained in the low temperature range and localization effects were observed. 23 The main obstacle remains to be preserving both the metallicity down to the lowest temperature and the two-dimensional nature of the electron gases by using proper oxygen deposition conditions. 23 In this article we explore the fabrication of an artificial LAO/STO interface, where the 2DEG is formed within a STO layer that was homoepitaxially grown on a (001) STO single-crystal.…”

mentioning

confidence: 99%

“…23 The main obstacle remains to be preserving both the metallicity down to the lowest temperature and the two-dimensional nature of the electron gases by using proper oxygen deposition conditions. 23 In this article we explore the fabrication of an artificial LAO/STO interface, where the 2DEG is formed within a STO layer that was homoepitaxially grown on a (001) STO single-crystal. We demonstrate that the 2DEG at the fabricated interfaces is not only metallic down to the lowest temperatures, but also superconducting.…”

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confidence: 99%

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Fabricating superconducting interfaces between artificially grown LaAlO3 and SrTiO3 thin films

Li¹,

Gariglio²,

Cancellieri³

et al. 2014

APL Materials

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Realization of a fully metallic two-dimensional electron gas at the interface between artificially-grown LaAlO 3 and SrTiO 3 thin films has been an exciting challenge. Here we present for the first time the successful realization of a superconducting 2DEG at interfaces between artificially-grown LaAlO 3 and SrTiO 3 thin films. Our results highlight the importance of two factors-the growth temperature and the SrTiO 3 termination. We use local friction force microscopy and transport measurements to determine that in normal growth conditions the absence of a robust metallic state at low temperature in the artificially-grown LaAlO 3 /SrTiO 3 interface is due to the nanoscale SrO segregation occurring on the SrTiO 3 film surface during the growth and the associated defects in the SrTiO 3 film. By adopting an extremely high SrTiO 3 growth temperature, we demonstrate a way to realize metallic, down to the lowest temperature, and superconducting 2DEG at interfaces between LaAlO 3 layers and artificially-grown SrTiO 3 thin films. This study paves the way to the realization of functional LaAlO 3 /SrTiO 3 superlattices and/or artificial LaAlO 3 /SrTiO 3 interfaces on other substrates.

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Section: -3mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Fabricating superconducting interfaces between artificially grown LaAlO3 and SrTiO3 thin films

Li¹,

Gariglio²,

Cancellieri³

et al. 2014

APL Materials

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“…Furthermore, a weak to strong localization 10, 11 and magnetic Kondo behavior 6 were reported in thicker samples, suggesting that a variety of conduction mechanisms were operating at these interfaces. Moreover the superconductivity at these interfaces was also shown to be sensitive to the thickness 2 of the over layer where the localization is suggested to be minimum.…”

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Evolution of variable range hopping in strongly localized two dimensional electron gas at NdAlO3/SrTiO3 (100) heterointerfaces

Annadi

Putra

Srivastava

et al. 2012

Applied Physics Letters

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We report evolution of the two-dimensional electron gas behavior at the NdAlO 3 /SrTiO 3 heterointerfaces with varying thicknesses of the NdAlO 3 overlayer. The samples with a thicker NdAlO 3 show strong localizations at low temperatures and the degree of localization is found to increase with the NdAlO 3 thickness. The T -1/3 temperature dependence of the sheet resistance at low temperatures and the magnetoresistance study reveal that the conduction is governed by a two-dimensional variable range hopping mechanism in this strong localized regime. We attribute this thickness dependence of the transport properties of the NdAlO 3 /SrTiO 3 interfaces to the interface strain induced by the overlayers. 2The discovery of the two dimensional electron gas (2DEG) at the LaAlO 3 /SrTiO 3 oxide hetero interface 1 has made this material system a primary candidate for applications in oxide electronics. This system has further triggered the interest of the community as novel phenomena, such as superconductivity and magnetism, 2-5 were observed at this interface and furthermore these properties were shown to be sensitive to the external parameters such as O 2 deposition pressure 6 and strain effects 7 at the interface. One of the characteristic features of the 2DEG is the overlayer thickness dependence 8,9 of its conductivity, where a thickness dependent metal to insulator transition (MIT) transition was observed at a critical thickness of LaAlO 3 overlayer.Furthermore, a weak to strong localization 10,11 and magnetic Kondo behavior 6 were reported in thicker samples, suggesting that a variety of conduction mechanisms were operating at these interfaces. Moreover the superconductivity at these interfaces was also shown to be sensitive to the thickness 2 of the over layer where the localization is suggested to be minimum. Very recently, we reported the formation of 2DEG at various polar/nonpolar oxide interfaces 12showing a stronger localization of 2DEG compared to that at the LaAlO 3 /SrTiO 3 interfaces. This stronger localization can possibly give rise to different transport properties, and thus its dependence on the overlayer thickness is very crucial to be investigated. LaAlO 3 /SrTiO 3 . 9 However, a significant observation can be made for the low temperature transport for the thicker NdAlO 3 /SrTiO 3 samples, i.e. below 15 K the variation in R s is more distinct indicating a different type of transport mechanism operating at low temperatures. Figure 2b shows the temperature dependenence of n s and  for the corresponding samples. For the thicker samples the n s decreases in the temperature range of 300-20 K, can be attributed to the localization of activated charge carriers at the interface. significantly towards the low temperatures, which is further evidence for strong localization in these samples. The low temperature behavior of R s , n s and  confirms the strong localization of carriers associated with a change of transport mechanism at low temperatures.In general, the observed low temperature sharp upturns in R ...

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Bandgap Control of the Oxygen‐Vacancy‐Induced Two‐Dimensional Electron Gas in SrTiO₃

Liu

Zeng

Deng

et al. 2014

Adv Materials Inter

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STO is central to modern oxide electronics since it serves as the main workhorse for complex functional oxide heterostructure fabrications. After the two-dimensional electron gas (2DEG) at the interface between STO and LAO had been unveiled, [7] a large number of exotic properties of the 2DEG were revealed such as a critical thickness for the appearance of conductivity, [8] Kondo effect, [9] interface superconductivity, [10] an electrically tunable ground state, [11,12] electronic phase separation [5] and recently discovered high-temperature superconductor-like gap behavior. [13] In addition, the practicability of monolithically integrated oxide electronics based on the LAO/STO interface system has been demonstrated. [14] As the research on the LAO/STO interface system is going on, the properties of STO itself have become a center of attention. For example, oxygen vacancies in STO have been a longstanding issue of debate in understanding the emergence of novel electronic and magnetic phases in the 2DEG. Additionally, a fundamental issue related to STO remaining up to now is that although STO single crystals are easy to make metallic with oxygen vacancies, [15,16] it is rather difficult to make an insulating STO thin film completely metallic via oxygen vacancies. Instead, oxygen-deficient STO films are typically semiconducting at low temperatures. [17][18][19][20] Besides, the 2DEG at the LAO/STO interface fabricated on STO films [21][22][23][24] is more localized at low temperatures than that fabricated on STO single crystals; [7] it was found that the insertion of a STO film layer degrades the LAO/STO interface significantly; [25,26] the fully metallic state of the LAO/STO interface based on STO films is achieved when STO films are deposited at a very high temperature of 1100 °C. [27] These perhaps indicate the presence of point defects/disorder in the STO films deposited at the typical temperature range of 600-800 °C.A 2DEG in STO-based heterostructures can be created via oxygen vacancies (2DEG-V) when the overlayer contains elements such as Al which have a strong affinity for oxygen. [28][29][30] Hence the 2DEG-V can be easy to realize by depositing an amorphous, nonpolar LAO (aLAO) film onto STO at room temperature. In this work, our focus is on the 2DEG-V at the interface between amorphous LAO films and STO films, and its relation to the bandgap of STO films, which was found to significantly increase due to the defective nature of STO thin films.In this work, we fabricated 2DEG-V heterostructures by depositing aLAO films on STO films that were pre-deposited on LAO single-crystal substrates. STO films of 150 nm thickness were deposited from a single-crystal STO target on (100)-oriented LAO singlecrystal substrates, using pulsed laser deposition (KrF laser λ = 248 nm) in 10 -2 Torr oxygen partial pressure at various temperatures ranging from 30 to 750 °C. After deposition, the STO films were cooled to room temperature in the deposition oxygen pressure. Amorphous 25-nm-thick LAO films were subsequently deposit...

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Localization of two-dimensional electron gas in LaAlO3/SrTiO3heterostructures

Cited by 39 publications

References 34 publications

Fabricating superconducting interfaces between artificially grown LaAlO3 and SrTiO3 thin films

Fabricating superconducting interfaces between artificially grown LaAlO3 and SrTiO3 thin films

Evolution of variable range hopping in strongly localized two dimensional electron gas at NdAlO3/SrTiO3 (100) heterointerfaces

Bandgap Control of the Oxygen‐Vacancy‐Induced Two‐Dimensional Electron Gas in SrTiO₃

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Localization of two-dimensional electron gas in LaAlO3/SrTiO3heterostructures

Cited by 39 publications

References 34 publications

Fabricating superconducting interfaces between artificially grown LaAlO3 and SrTiO3 thin films

Fabricating superconducting interfaces between artificially grown LaAlO3 and SrTiO3 thin films

Evolution of variable range hopping in strongly localized two dimensional electron gas at NdAlO3/SrTiO3 (100) heterointerfaces

Bandgap Control of the Oxygen‐Vacancy‐Induced Two‐Dimensional Electron Gas in SrTiO3

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Bandgap Control of the Oxygen‐Vacancy‐Induced Two‐Dimensional Electron Gas in SrTiO₃