期刊
SURFACE SCIENCE
卷 606, 期 3-4, 页码 554-558出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.susc.2011.11.029
关键词
Strontium titanate; Surface preparation; X-ray photoemission
资金
- U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [10122]
- Department of Energy's Office of Biological and Environmental Research at Pacific Northwest National Laboratory
We show that the HF acid etch commonly used to prepare SrTiO3(001) for heteroepitaxial growth of complex oxides results in a non-negligible level of F doping within the terminal surface layer of TiO2. Using a combination of x-ray photoelectron spectroscopy and scanned angle x-ray photoelectron diffraction, we determine that on average similar to 13% of the O anions in the surface layer are replaced by F. but that F does not occupy O sites in deeper layers. Despite this perturbation to the surface, the Fermi level remains unpinned, and the surface-state density, which determines the amount of band bending, is driven by factors other than F doping. The presence of F at the STO surface is expected to result in lower electron mobilities at complex oxide hetero-junctions involving STO substrates because of impurity scattering. Unintentional F doping can be substantially reduced by replacing the HF-etch step with a boil in deionized water, which in conjunction with an oxygen tube furnace anneal, leaves the surface flat and TiO2 terminated. (C) 2011 Elsevier B.V. All rights reserved.
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