Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of vacancy-related polaron states at the surface of anatase
  and rutile TiO2 by high-resolution photoelectron spectroscopy   Defects in the surface region of a reducible oxide, as TiO2, have a profound
effect on applications, while their nature is very much influenced by the
possibility of small polaron formation. Here, we probe rutile (110) and anatase
(101) single crystals via high-resolution ultraviolet photoelectron
spectroscopy and resolve multiple components of the well-known defect state in
the band gap. In rutile, we find two at VBM+2.1 eV and VBM+1.4 eV, which we
assign to subsurface polaron traps and vacancy-bound states, respectively,
confirming the predicted partial suppression of polaron formation at high
vacancy concentration. New defects are created in situ on the anatase surface
by the synchrotron beam. We assign a component at VBM+2.3 eV, which can be
removed by annealing, to polaron states associated with surface oxygen
vacancies. We also identify a second component at VBM+1.6 eV, which can not be
removed by annealing, and is too deep to be associated with oxygen vacancies.

13
The categories of this paper are: quant-ph
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
6
The categories of this paper are: astro-ph
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
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The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
16
The categories of this paper are: stat