Band Offsets at the Epitaxial Anatase TiO2/n-SrTiO3(001) Interface

Journal Article · Sun Mar 01 04:00:00 EST 2009 · Surface Science, 603(5):771-780

DOI:https://doi.org/10.1016/j.susc.2009.01.023· OSTI ID:951816

Chambers, Scott A; Ohsawa, Takeo; Wang, Chong M; Lyubinetsky, Igor; Jaffe, John E

We have used high-energy-resolution x-ray photoelectron spectroscopy to measure valence band offsets at the epitaxial anatase TiO2(002)/n-SrTiO3(001) heterojunction prepared by molecular beam epitaxy, Within experimental error, the valance band offset is zero for anatase thicknesses between 1 and 7 monolayers. The conduction band offset is also zero by virtue of the fact that both anatase and SrTiO3 exhibit the same bandgap value (~3.2 eV). In one set of experiments, the interface included a partial monolayer of fluorine remaining from the HF etch that was used to prepare the substrate. The F could not be removed without Ar ion sputtering and annealing, which in turn resulted in ~0.15 eV of band bending, indicating the presence of interfacial defects. The band offsets were measured to be approximately 0 eV as well when the F was removed. Density functional theory predicts the valence band offset for the clean interface to be 0.5 eV. Inclusion of interfacial F reduces the theoretical band offset to 0.2 eV, much closer to experiment, and suggesting that the interface dipoles created by F and sputter defects have a major effect on the band offset.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 951816
• Report Number(s): PNNL-SA-62398; 19392; KC0302010
• Journal Information: Surface Science, 603(5):771-780, Journal Name: Surface Science, 603(5):771-780 Journal Issue: 5 Vol. 603; ISSN SUSCAS; ISSN 0039-6028
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANNEALING
BENDING
DEFECTS
DIPOLES
Environmental Molecular Sciences Laboratory
FLUORINE
FUNCTIONALS
HETEROJUNCTIONS
MOLECULAR BEAM EPITAXY
SPUTTERING
VALENCE
X-RAY PHOTOELECTRON SPECTROSCOPY