Non-conducting interfaces of LaAlO3/SrTiO3 produced in sputter deposition: The role of stoichiometry

Dildar, I.M.; Boltje, D.B.; Hesselberth, M.H.S.; Aarts, J.; Xu, Qiaoling; Zandbergen, H.W.; Harkema, Sybolt

doi:10.1063/1.4798828

Cited by 31 publications

(22 citation statements)

References 16 publications

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“…This measurement further supports the result that La/Alr0.97 ± 0.03 is a necessary condition for obtaining a 2-DEL at La ( 3 interfaces and suggests that this result is independent of the growth method used as long as the growth conditions do not promote extrinsic defects. The non-conducting interfaces reported in sputtered films that are found to be La-rich 35 is also consistent with our result (see Supplementary Note 2).…”

Section: Mosaic Growth Experimentsupporting

confidence: 82%

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

et al. 2013

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Emergent phenomena, including superconductivity and magnetism, found in the two-dimensional electron liquid (2-DEL) at the interface between the insulators lanthanum aluminate (LaAlO 3 ) and strontium titanate (SrTiO 3 ) distinguish this rich system from conventional 2D electron gases at compound semiconductor interfaces. The origin of this 2-DEL, however, is highly debated, with focus on the role of defects in the SrTiO 3 , while the LaAlO 3 has been assumed perfect. Here we demonstrate, through experiments and firstprinciple calculations, that the cation stoichiometry of the nominal LaAlO 3 layer is key to 2-DEL formation: only Al-rich LaAlO 3 results in a 2-DEL. Although extrinsic defects, including oxygen deficiency, are known to render LaAlO 3 /SrTiO 3 samples conducting, our results show that in the absence of such extrinsic defects an interface 2-DEL can form. Its origin is consistent with an intrinsic electronic reconstruction occurring to counteract a polarization catastrophe. This work provides insight for identifying other interfaces where emergent behaviours await discovery.

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Section: Mosaic Growth Experimentsupporting

confidence: 82%

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

et al. 2013

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“…The resulting interface conductance strongly depends on the oxygen pressure, 1,5 indicating that the formation of oxygen vacancies plays a role in the conductance as well. This is also found in experiments involving sputter deposition, 6 or post-annealing. 7 In view of the influence of the termination layer, the atomic structure of the starting surface is of obvious importance; however, relatively little research has been done to clarify this at actual growth conditions, which entail both a high temperature and a certain oxygen pressure.…”

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confidence: 52%

The surface structure of SrTiO3 at high temperatures under influence of oxygen

Hesselberth

Molen

Aarts

2014

Applied Physics Letters

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“…Recent observations have also indicated that the cationic stoichiometry, e.g., the La/Al ratio in LaAlO3 film, may affect the electrical properties of LaAlO3/SrTiO3 18,48,49 shows the atomically flat surface with unit cell steps. The growth target was LaAlO3 single crystal, also obtained from Crystec.…”

Section: /33mentioning

confidence: 99%

Mechanisms of charge transfer and redistribution in LaAlO3/SrTiO3 revealed by high-energy optical conductivity

et al. 2014

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In condensed matter physics the quasi two-dimensional electron gas at the interface of two different insulators, polar LaAlO3 on nonpolar SrTiO3 (LaAlO3/SrTiO3) is a spectacular and surprising observation. This phenomenon is LaAlO3 film thickness dependent and may be explained by the polarization catastrophe model, in which a charge transfer of 0.5e(-) from the LaAlO3 film into the LaAlO3/SrTiO3 interface is expected. Here we show that in conducting samples (≥ 4 unit cells of LaAlO3) there is indeed a ~0.5e(-) transfer from LaAlO3 into the LaAlO3/SrTiO3 interface by studying the optical conductivity in a broad energy range (0.5-35 eV). Surprisingly, in insulating samples (≤ 3 unit cells of LaAlO3) a redistribution of charges within the polar LaAlO3 sublayers (from AlO2 to LaO) as large as ~0.5e(-) is observed, with no charge transfer into the interface. Hence, our results reveal the different mechanisms for the polarization catastrophe compensation in insulating and conducting LaAlO3/SrTiO3 interfaces.

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Non-conducting interfaces of LaAlO3/SrTiO3 produced in sputter deposition: The role of stoichiometry

Cited by 31 publications

References 16 publications

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

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

The surface structure of SrTiO3 at high temperatures under influence of oxygen

Mechanisms of charge transfer and redistribution in LaAlO3/SrTiO3 revealed by high-energy optical conductivity

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