Tuning Up or Down the Critical Thickness in LaAlO<sub>3</sub> /SrTiO<sub>3</sub> through In Situ Deposition of Metal Overlayers.
basic_science · Level V
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- Record sourced from PubMed, PMID 28505388.
- Also identified by DOI 10.1002/adma.201700486.
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Abstract
The quasi 2D electron system (q2DES) that forms at the interface between LaAlO<sub>3</sub> and SrTiO<sub>3</sub> has attracted much attention from the oxide electronics community. One of its hallmark features is the existence of a critical LaAlO<sub>3</sub> thickness of 4 unit-cells (uc) for interfacial conductivity to emerge. In this paper, the chemical, electronic, and transport properties of LaAlO<sub>3</sub> /SrTiO<sub>3</sub> samples capped with different metals grown in a system combining pulsed laser deposition, sputtering, and in situ X-ray photoemission spectroscopy are investigated. The results show that for metals with low work function a q2DES forms at 1-2 uc of LaAlO<sub>3</sub> and is accompanied by a partial oxidation of the metal, a phenomenon that affects the q2DES properties and triggers the formation of defects. In contrast, for noble metals, the critical thickness is increased above 4 uc. The results are discussed in terms of a hybrid mechanism that incorporates electrostatic and chemical effects.