Quasi-two-dimensional electron gas at the interface of γ-Al2O3/SrTiO3 heterostructures grown by atomic layer deposition

We report the formation of a quasi-two-dimensional electron gas (2-DEG) at the interface of γ-Al2O3/TiO2-terminated SrTiO3 (STO) grown by atomic layer deposition (ALD). The ALD growth of Al2O3 on STO(001) single crystal substrates was performed at temperatures in the range of 200–345 °C. Trimethylal...

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Veröffentlicht in:Journal of applied physics 2015-09, Vol.118 (11)
Hauptverfasser: Ngo, Thong Q., Goble, Nicholas J., Posadas, Agham, Kormondy, Kristy J., Lu, Sirong, McDaniel, Martin D., Jordan-Sweet, Jean, Smith, David J., Gao, Xuan P. A., Demkov, Alexander A., Ekerdt, John G.
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container_issue 11
container_start_page
container_title Journal of applied physics
container_volume 118
creator Ngo, Thong Q.
Goble, Nicholas J.
Posadas, Agham
Kormondy, Kristy J.
Lu, Sirong
McDaniel, Martin D.
Jordan-Sweet, Jean
Smith, David J.
Gao, Xuan P. A.
Demkov, Alexander A.
Ekerdt, John G.
description We report the formation of a quasi-two-dimensional electron gas (2-DEG) at the interface of γ-Al2O3/TiO2-terminated SrTiO3 (STO) grown by atomic layer deposition (ALD). The ALD growth of Al2O3 on STO(001) single crystal substrates was performed at temperatures in the range of 200–345 °C. Trimethylaluminum and water were used as co-reactants. In situ reflection high energy electron diffraction, ex situ x-ray diffraction, and ex situ cross-sectional transmission electron microscopy were used to determine the crystallinity of the Al2O3 films. As-deposited Al2O3 films grown above 300 °C were crystalline with the γ-Al2O3 phase. In situ x-ray photoelectron spectroscopy was used to characterize the Al2O3/STO interface, indicating that a Ti3+ feature in the Ti 2p spectrum of STO was formed after 2–3 ALD cycles of Al2O3 at 345 °C and even after the exposure to trimethylaluminum alone at 300 and 345 °C. The interface quasi-2-DEG is metallic and exhibits mobility values of ∼4 and 3000 cm2 V−1 s−1 at room temperature and 15 K, respectively. The interfacial conductivity depended on the thickness of the Al2O3 layer. The Ti3+ signal originated from the near-interfacial region and vanished after annealing in an oxygen environment.
doi_str_mv 10.1063/1.4930575
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In situ x-ray photoelectron spectroscopy was used to characterize the Al2O3/STO interface, indicating that a Ti3+ feature in the Ti 2p spectrum of STO was formed after 2–3 ALD cycles of Al2O3 at 345 °C and even after the exposure to trimethylaluminum alone at 300 and 345 °C. The interface quasi-2-DEG is metallic and exhibits mobility values of ∼4 and 3000 cm2 V−1 s−1 at room temperature and 15 K, respectively. The interfacial conductivity depended on the thickness of the Al2O3 layer. 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(BNL), Upton, NY (United States)</aucorp><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Quasi-two-dimensional electron gas at the interface of γ-Al2O3/SrTiO3 heterostructures grown by atomic layer deposition</atitle><jtitle>Journal of applied physics</jtitle><date>2015-09-21</date><risdate>2015</risdate><volume>118</volume><issue>11</issue><issn>0021-8979</issn><eissn>1089-7550</eissn><abstract>We report the formation of a quasi-two-dimensional electron gas (2-DEG) at the interface of γ-Al2O3/TiO2-terminated SrTiO3 (STO) grown by atomic layer deposition (ALD). The ALD growth of Al2O3 on STO(001) single crystal substrates was performed at temperatures in the range of 200–345 °C. Trimethylaluminum and water were used as co-reactants. In situ reflection high energy electron diffraction, ex situ x-ray diffraction, and ex situ cross-sectional transmission electron microscopy were used to determine the crystallinity of the Al2O3 films. As-deposited Al2O3 films grown above 300 °C were crystalline with the γ-Al2O3 phase. In situ x-ray photoelectron spectroscopy was used to characterize the Al2O3/STO interface, indicating that a Ti3+ feature in the Ti 2p spectrum of STO was formed after 2–3 ALD cycles of Al2O3 at 345 °C and even after the exposure to trimethylaluminum alone at 300 and 345 °C. The interface quasi-2-DEG is metallic and exhibits mobility values of ∼4 and 3000 cm2 V−1 s−1 at room temperature and 15 K, respectively. The interfacial conductivity depended on the thickness of the Al2O3 layer. The Ti3+ signal originated from the near-interfacial region and vanished after annealing in an oxygen environment.</abstract><cop>Melville</cop><pub>American Institute of Physics</pub><doi>10.1063/1.4930575</doi><orcidid>https://orcid.org/0000-0002-1148-4915</orcidid><orcidid>https://orcid.org/0000000211484915</orcidid><oa>free_for_read</oa></addata></record>
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source AIP Journals Complete; Alma/SFX Local Collection
subjects Aluminum oxide
Applied physics
ATOMIC AND MOLECULAR PHYSICS
Atomic layer deposition
Atomic layer epitaxy
Crystal structure
Crystallinity
Electron diffraction
Electron gas
Electrons
Energy transmission
Heterostructures
Single crystals
Strontium titanates
Substrates
Thickness
Thin films
Titanium
Titanium dioxide
Transition metal oxides
Transitional aluminas
Transmission electron microscopy
Two-dimensional electron gas
X-ray diffraction
X-ray photoelectron spectroscopy
title Quasi-two-dimensional electron gas at the interface of γ-Al2O3/SrTiO3 heterostructures grown by atomic layer deposition
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