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Title: Polar asymmetry of La{sub (1−δ)}Al{sub (1+δ)}O{sub 3}/SrTiO{sub 3} heterostructures probed by optical second harmonic generation

By combining transport measurements and optical second harmonic generation, we have investigated heterostructures formed between crystalline thin films of LaAlO{sub 3}, with varying stoichiometry and TiO{sub 2}-terminated SrTiO{sub 3}(001) substrates. Optical second harmonic generation directly probes the polarity of these heterostructures, thus complementing the transport data. The stoichiometry and the growth temperature are found to be critical parameters for controlling both the interfacial conductivity and the heterostructure polarity. In agreement with the previous work, all of the samples display an insulator-to-metal transition in the Al-reach region, with the conductivity first increasing and then saturating at the highest Al/La ratios. The second harmonic signal also increases as a function of the Al/La ratio, but, at the highest growth temperature, it does not saturate. This unusual behavior is consistent with the formation of an ordered structure of defect dipoles in the LaAlO{sub 3} film caused by the off-centering of excess Al atoms in agreement with the theory.
Authors:
; ; ;  [1] ;  [2] ; ;  [3] ;  [3] ;  [4]
  1. CNR-SPIN and Università Federico II, Monte S. Angelo, via Cintia, Napoli 80126 (Italy)
  2. Peter Grünberg Institute (PGI9-IT), JARA- Fundamentals of Future Information Technology, Research Centre Jülich, Jülich D-52425 (Germany)
  3. Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States)
  4. (United States)
Publication Date:
OSTI Identifier:
22482028
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 10; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALUMINATES; ASYMMETRY; DIPOLES; HARMONIC GENERATION; LANTHANUM COMPOUNDS; METALS; OZONE; SIGNALS; STOICHIOMETRY; STRONTIUM TITANATES; SUBSTRATES; THIN FILMS; TITANIUM OXIDES