Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structures, optical properties, and electrical transport processes of
  SnO$_2$ films with oxygen deficiencies   The structures, optical and electrical transport properties of SnO$_2$ films,
fabricated by rf sputtering method at different oxygen partial pressures, were
systematically investigated. It has been found that preferred growth
orientation of SnO$_2$ film is strongly related to the oxygen partial pressure
during deposition, which provides an effective way to tune the surface texture
of SnO$_2$ film. All films reveal relatively high transparency in the visible
range, and both the transmittance and optical band gap increase with increasing
oxygen partial pressure. The temperature dependence of resisitivities was
measured from 380 K down to liquid helium temperatures. At temperature above
$\sim 80$ K, besides the nearest-neighbor-hopping process, thermal activation
processes related to two donor levels ($\sim 30$ and $\sim 100$ meV below the
conduction band minimum) of oxygen vacancies are responsible for the charge
transport properties. Below $\sim 80$ K, Mott variable-range-hopping conduction
process governs the charge transport properties at higher temperatures, while
Efros-Shklovskii variable-range-hopping conduction process dominates the
transport properties at lower temperatures. Distinct crossover from Mott type
to Efros-Shklovskii type variable-range-hopping conduction process at several
to a few tens kelvin are observed for all SnO$_2$ films.

31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th