Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Enhancing electrical and thermoelectrical properties of $\mathrm{WO}_3$
  thin films by spray pyrolysis technique   Tungsten trioxide $\mathrm{WO}_3$ thin films have been deposited on glass
substrates by spray pyrolysis technique with three different rates R$_1=1$
ml/min (sample A$_1$), R$_2=3$ ml/min (sample A$_2$) and R$_3=7$ ml/min (sample
A$_3$). We have then annealed all samples for 2 h at 500 $^\circ$C in air.
Structural, morphological, optical and electrical properties of $\mathrm{WO}_3$
thin films are investigated in detail. According to the FESEM images, all
layers are formed in various circular strings with different diameters. The
diameter of each strain decreases when the deposition rate increases. The XRD
structural analysis indicates that before annealing, except the lowest
deposition rate sample R$_1$ with a polycrystalline nature and mixed tetragonal
and hexagonal phases, other samples are grown in an amorphous phase. After
annealing, sample A$_2$ (with rate R$_2=3$ ml/min) remains in an amorphous
phase, while samples A$_1$ and A$_3$ (with the corresponding rates R$_1=1$
ml/min and R$_3=7$ ml/min respectively) are polycrystalline. Moreover, from
UV-Vis. spectra analysis we found that by increasing spray rate the band gap of
the layers monotonically decreases. This phenomenon is the result of
attenuation of the quantum confined effect. The thermoelectric properties
confirm being $n$-type conductivity of the layers, also variation in the
current-voltage characteristic is in accordance with the oxygen vacancies
sites. We found that the sample A$_3$ with the highest rate has lowest
resistivity.

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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs