Experimental determination of valence band maxima for SrTiO₃,TiO₂, and SrO and the associated valence band offsets with Si(001)

Conference · Fri Aug 20 00:00:00 EDT 2004

DOI:https://doi.org/10.1116/1.1768525· OSTI ID:963250

Chambers, Scott A. ^[1]; Droubay, Timothy C. ^[1]; Kaspar, Tiffany C. ^[1]; Gutowski, Maciej S. ^[1]

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1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

We address the issue of accurate determination of the valence band maximum (VBM) for SrTiO₃(001) single crystals and epitaxial films, as well as TiO₂(001) anatase and SrO epitaxial films. These measurements are of critical importance in determining valence band offsets in heterojunctions of these oxides with Si. Three different methods are analyzed: (1) fitting a Gaussian broadened theoretical density of states to the x-ray photoelectron valence band spectrum; (2) finding the intersection of a regression line that spans the linear portion of the x-ray photoelectron valence band leading edge with the background between the valence band maximum and the Fermi level; and (3) determining the energy at which high-resolution ultraviolet photoemission intensity at the leading edge goes to zero. We find that method 1 yields physically unreasonable results when used in conjunction with density functional theory because the latter does not predict the detailed shape of the valence bands in these oxides with sufficient accuracy. In contrast, methods 2 and 3 give physically reasonable results that are in good mutual agreement. The difference in VBM between method 1 and methods 2 and 3 is 0.4–0.6 eV, depending on the oxide. Methods 2 and 3 yield the most reliable VBM, provided the experiments are carried out with adequate energy resolution.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 963250
• Report Number(s): PNNL-SA-43069; KC0302010; TRN: US200917%%204
• Resource Relation: Conference: 31st Conference on the Physics and Chemistry of Semiconductor Interfaces (PCSI). Published in Journal of Vacuum Science and Technology B, 22(4):2205-2215
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
STRONTIUM OXIDES
TITANIUM OXIDES
ENERGY RESOLUTION
FERMI LEVEL
HETEROJUNCTIONS
MONOCRYSTALS
VALENCE
MEASURING METHODS
COMPARATIVE EVALUATIONS
Valance
band
maximum
ultraviolet
photoemission