Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hydrogen Diffusion and Stabilization in Single-crystal VO2
  Micro/nanobeams by Direct Atomic Hydrogenation   We report measurements of the diffusion of atomic hydrogen in single
crystalline VO2 micro/nanobeams by direct exposure to atomic hydrogen, without
catalyst. The atomic hydrogen is generated by a hot filament, and the doping
process takes place at moderate temperature (373 K). Undoped VO2 has a
metal-to-insulator phase transition at ~340 K between a high-temperature,
rutile, metallic phase and a low-temperature, monoclinic, insulating phase with
a resistance exhibiting a semiconductor-like temperature dependence. Atomic
hydrogenation results in stabilization of the metallic phase of VO2
micro/nanobeams down to 2 K, the lowest point we could reach in our measurement
setup. Based on observing the movement of the hydrogen diffusion front in
single crystalline VO2 beams, we estimate the diffusion constant for hydrogen
along the c-axis of the rutile phase to be 6.7 x 10^{-10} cm^2/s at
approximately 373 K, exceeding the value in isostructural TiO2 by ~ 38x.
Moreover, we find that the diffusion constant along the c-axis of the rutile
phase exceeds that along the equivalent a-axis of the monoclinic phase by at
least three orders of magnitude. This remarkable change in kinetics must
originate from the distortion of the "channels" when the unit cell doubles
along this direction upon cooling into the monoclinic structure. Ab initio
calculation results are in good agreement with the experimental trends in the
relative kinetics of the two phases. This raises the possibility of a
switchable membrane for hydrogen transport.

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The categories of this paper are: hep-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: adap-org
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The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ph
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The categories of this paper are: q-alg
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The categories of this paper are: comp-gas