N incorporation and electronic structure in N-doped TiO2(110) rutile

We describe the growth and properties of well-defined epitaxial TiO2-xNx rutile for the first time. A mixed beam of atomic N and O radicals was prepared in an electron cyclotron resonance plasma source and Ti was supplied from a high-temperature effusion cell or an electron beam evaporator, dependin...

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Bibliographic Details
Published in:Surface science 2007-04, Vol.601 (7), p.1754-1762
Main Authors: CHEUNG, S. H, NACHIMUTHU, P, JOLY, A. G, ENGELHARD, M. H, BOWMAN, M. K, CHAMBERS, S. A
Format: Article
Language:English
Subjects:
ABSORPTION
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
DOPED MATERIALS
ELECTRONIC STRUCTURE
Environmental Molecular Sciences Laboratory
Exact sciences and technology
INTERSTITIALS
MATERIALS SCIENCE
NITRATES
NITRIC OXIDE
NITROGEN
Physics
RUTILE
TITANIUM OXIDES
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Summary:We describe the growth and properties of well-defined epitaxial TiO2-xNx rutile for the first time. A mixed beam of atomic N and O radicals was prepared in an electron cyclotron resonance plasma source and Ti was supplied from a high-temperature effusion cell or an electron beam evaporator, depending on the required flux. A very high degree of structural quality is generally observed for films grown under optimized anion-rich conditions. N substitutes for O in the lattice, but only at the 1 at.% level, and is present as N3-. Epitaxial growth of TiO2 and TiO2-xNx rutile prepared under anion-rich conditions is accompanied by Ti indiffusion, leading to interstitial Ti (Tii), which is a shallow donor in rutile. Our data strongly suggest that Tii donor electrons compensate holes associated with substitutional N2- (i.e., Ti(III)+N2- > Ti(IV)+N3-), leading to highly resistive or weakly n-type, but not p-type material. Ti 2p core-level line shape analysis reveals hybridization of N and Ti, as expected for substitutional N. Ti-N hybridized states fall in the gap just above the VBM, and extend the optical absorption well into the visible.
ISSN:0039-6028
1879-2758
DOI:10.1016/j.susc.2007.01.051