  Tin (IV) oxide (SnO2) sols have been synthesized from SnCl2.2H2O precursor
solution by applying two different processing conditions. The prepared sols
were then deposited on UV-Ozone treated quartz and soda lime glass (SLG)
substrates by spin coating. The as-synthesized film was soft-baked at about 100
deg. C. for 10 min. This process was repeated five times to get a compact film,
followed by air-annealing at 250 deg. C. for 2 hours. The pristine and annealed
films were characterized by UV-Vis-NIR spectroscopy, Grazing Incident X-Ray
Diffraction (GIXRD), and Field Emission Scanning Electron Microscope (FESEM).
The effect of the substrate surface was investigated by measuring the contact
angles with De-Ionized (DI) water. UV-Ozone treatment of substrate provides a
cleaner surface to grow a homogeneous film. The electrical resistivity of
annealed thin films was carried out by a four-point-collinear probe employing
the current reversal technique and found in the range of approx. 2x10^3 to
3x10^3 Ohm-cm. Film thickness was found in the range of approx. 137-285 nm,
measured by a stylus profilometer. UV-VIs-NIR Transmission data revealed that
all the thin film samples showed maximum (82-89) % transmission in the visible
range. The optical bandgap of the thin films was estimated to be approx.
3.75-4.00 eV and approx. 3.78-4.35 eV for the films grown on SLG and quartz
substrates, respectively.
