Quasi-two-dimensional electron gas at the interface of γ-Al{sub 2}O{sub 3}/SrTiO{sub 3} heterostructures grown by atomic layer deposition

Journal Article · Mon Sep 21 00:00:00 EDT 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4930575· OSTI ID:22489509

Ngo, Thong Q.; McDaniel, Martin D.; Goble, Nicholas J.; Gao, Xuan P. A. ^[1]; Posadas, Agham; Kormondy, Kristy J.; Demkov, Alexander A. ^[2]; Lu, Sirong ^[3]; Jordan-Sweet, Jean ^[4]; Smith, David J. ^[5]

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1. Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106 (United States)
2. Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)
3. School of Engineering for Matter, Transport and Engineering, Arizona State University, Tempe, Arizona 85287 (United States)
4. IBM T.J. Watson Research Center, Yorktown Heights, New York 10598 (United States)
5. Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)

We report the formation of a quasi-two-dimensional electron gas (2-DEG) at the interface of γ-Al{sub 2}O{sub 3}/TiO{sub 2}-terminated SrTiO{sub 3} (STO) grown by atomic layer deposition (ALD). The ALD growth of Al{sub 2}O{sub 3} 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 Al{sub 2}O{sub 3} films. As-deposited Al{sub 2}O{sub 3} films grown above 300 °C were crystalline with the γ-Al{sub 2}O{sub 3} phase. In situ x-ray photoelectron spectroscopy was used to characterize the Al{sub 2}O{sub 3}/STO interface, indicating that a Ti{sup 3+} feature in the Ti 2p spectrum of STO was formed after 2–3 ALD cycles of Al{sub 2}O{sub 3} 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 cm{sup 2} V{sup −1} s{sup −1} at room temperature and 15 K, respectively. The interfacial conductivity depended on the thickness of the Al{sub 2}O{sub 3} layer. The Ti{sup 3+} signal originated from the near-interfacial region and vanished after annealing in an oxygen environment.

• OSTI ID: 22489509
• Journal Information: Journal of Applied Physics, Vol. 118, Issue 11; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALUMINIUM OXIDES
ELECTRON DIFFRACTION
ELECTRON GAS
INTERFACES
MONOCRYSTALS
SIGNALS
SPECTRA
STRONTIUM TITANATES
SUBSTRATES
TITANIUM IONS
TITANIUM OXIDES
TRANSMISSION ELECTRON MICROSCOPY
TWO-DIMENSIONAL SYSTEMS
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY