Disentanglement of growth dynamic and thermodynamic effects in LaAlO3/SrTiO3 heterostructures

Xu, Chencheng; Bäumer, Christoph; Heinen, R.; Hoffmann‐Eifert, Susanne; Gunkel, Felix; Dittmann, Ralf W.

doi:10.1038/srep22410

Cited by 35 publications

(62 citation statements)

References 53 publications

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“…For this, we choose LAO grown on STO as it is a very p ox sensitive system. This system shows interface conduction, when the STO substrate is not reduced, and additional bulk conduction, when STO is reduced7162123. Thus LAO/STO has the advantage of a measurable sheet carrier concentration at room temperature even if the STO substrate is not reduced.…”

Section: Relevance For Low Pressure Depositionsmentioning

confidence: 98%

“…Another explanation often found in literature is the oxidization of the growing thin film by the STO substrate, eventually resulting in the reduction of the substrate293031. However, as soon as the plume is turned off one would expect the oxygen content of the sample to approach the equilibrium value and thus to reoxidize at a certain rate within the PLD chamber21.…”

mentioning

confidence: 98%

“…An example for the importance of the oxygen pressure during growth is the LaAlO 3 (LAO)/STO heterostructure. LAO/STO is well known for showing interface conductivity between two otherwise insulating materials716181920212223. However, if the STO substrate is reduced during low oxygen pressure deposition a strong contribution of the bulk conduction of the STO is measurable67, while a deposition at high oxygen pressures can result in an undesirably high resistance1820.…”

mentioning

confidence: 99%

“…Numerous examples can be found in literature for the reduction of STO substrates during pulsed laser depositions for physical oxygen pressures below 10 −5 mbar6711161718202122. This opposes the results of chemically controlled reducing atmosphere annealing experiments (H 2 /Ar/O 2 mixtures), for which the sample is, in opposite to vacuum annealing, under a physical pressure of 1 bar.…”

mentioning

confidence: 99%

“…Being able to explain the reduction of STO during annealing, we disentangle the reduction of STO during depositions. We do so using LAO growth on STO due to its oxygen pressure sensitivity7162123. We are able to separate influences induced by the plume from influences of an insufficient supply of oxygen and influences of the measurement devices.…”

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confidence: 99%

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Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

Hensling

Gunkel

et al. 2017

Sci Rep

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The reduction of oxides during annealing and growth in low pressure processes is a widely known problem. We hence investigate the influence of mere annealing and of growth in vacuum systems to shed light on the reasons behind the reduction of perovskites. When comparing the existing literature regarding the reduction of the perovskite model material SrTiO3 it is conspicuous that one finds different oxygen pressures required to achieve reduction for vacuum annealing and for chemically controlled reducing atmospheres. The unraveling of this discrepancy is of high interest for low pressure physical vapor depositions of thin films heterostructures to gain further understanding of the reduction of the SrTiO3. For thermal annealing, our results prove the attached measurement devices (mass spectrometer/ cold cathode gauge) to be primarily responsible for the reduction of SrTiO3 in the deposition chamber by shifting the thermodynamic equilibrium to a more reducing atmosphere. We investigated the impact of our findings on the pulsed laser deposition growth at low pressure for LaAlO3/SrTiO3. During deposition the reduction triggered by the presence of the laser plume dominates and the impact of the measurement devices plays a minor role. During post annealing a complete reoxidization of samples is inhibited by an insufficient supply of oxygen.

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Section: Relevance For Low Pressure Depositionsmentioning

confidence: 98%

mentioning

confidence: 98%

mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

Hensling

Gunkel

et al. 2017

Sci Rep

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Epitaxial Oxides on Semiconductors: From Fundamentals to New Devices

Kumah

Ngai

Kornblum

2019

Adv Funct Materials

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Functional oxides are an untapped resource for futuristic devices and functionalities. These functionalities can range from high temperature superconductivity to multiferroicity and novel catalytic schemes. The most prominent route for transforming these ideas from a single device in the lab to practical technologies is by integration with semiconductors. Moreover, coupling oxides with semiconductors can herald new and unexpected functionalities that exist in neither of the individual materials. Therefore, oxide epitaxy on semiconductors provides a materials platform for novel device technologies. As oxides and semiconductors exhibit properties that are complementary to one another, epitaxial heterostructures comprised of the two are uniquely poised to deliver rich functionalities. This review discusses recent advancements in the growth of epitaxial oxides on semiconductors, and the electronic and physical structure of their interfaces. Leaning on these fundamentals and practicalities, the material behavior and functionality of semiconductor-oxide heterostructures is discussed, and their potential as device building blocks is highlighted. The culmination of this discussion is a review of recent advances in the development of prototype devices based on semiconductor-oxide heterostructures, in areas ranging from silicon photonics to photocatalysis. This overview is intended to stimulate ideas for new concepts of functional devices and lay the groundwork for their realization.

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Identifying Ionic and Electronic Charge Transfer at Oxide Heterointerfaces

et al. 2020

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The ability to tailor oxide heterointerfaces has led to novel properties in low‐dimensional oxide systems. A fundamental understanding of these properties is based on the concept of electronic charge transfer. However, the electronic properties of oxide heterointerfaces crucially depend on their ionic constitution and defect structure: ionic charges contribute to charge transfer and screening at oxide interfaces, triggering a thermodynamic balance of ionic and electronic structures. Quantitative understanding of the electronic and ionic roles regarding charge‐transfer phenomena poses a central challenge. Here, the electronic and ionic structure is simultaneously investigated at the prototypical charge‐transfer heterointerface, LaAlO3/SrTiO3. Applying in situ photoemission spectroscopy under oxygen ambient, ionic and electronic charge transfer is deconvoluted in response to the oxygen atmosphere at elevated temperatures. In this way, both the rich and variable chemistry of complex oxides and the associated electronic properties are equally embraced. The interfacial electron gas is depleted through an ionic rearrangement in the strontium cation sublattice when oxygen is applied, resulting in an inverse and reversible balance between cation vacancies and electrons, while the mobility of ionic species is found to be considerably enhanced as compared to the bulk. Triggered by these ionic phenomena, the electronic transport and magnetic signature of the heterointerface are significantly altered.

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Disentanglement of growth dynamic and thermodynamic effects in LaAlO3/SrTiO3 heterostructures

Cited by 35 publications

References 53 publications

Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

Epitaxial Oxides on Semiconductors: From Fundamentals to New Devices

Identifying Ionic and Electronic Charge Transfer at Oxide Heterointerfaces

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