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Title: 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

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 vanishedmore » after annealing in an oxygen environment.« less
Authors:
; ;  [1] ; ;  [2] ; ; ;  [3] ;  [4] ;  [5] ;  [6]
  1. Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States)
  2. Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106 (United States)
  3. Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)
  4. School of Engineering for Matter, Transport and Engineering, Arizona State University, Tempe, Arizona 85287 (United States)
  5. IBM T.J. Watson Research Center, Yorktown Heights, New York 10598 (United States)
  6. Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)
Publication Date:
OSTI Identifier:
22489509
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 11; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
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