Effect of substrate surface on the wide bandgap SnO 2 thin films grown by spin coating

Tin (IV) oxide (SnO 2 ) sols have been synthesized from SnCl 2 ·2H 2 O 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 °C for 10 min. This process was repeated 5 times to get a compact film, followed by air annealing at 250 °C for 2 h. 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 ~ 2 × 10 3 to 3 × 10 3 Ω·cm. Film thickness was found in the range of ~ 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 ~ 3.75–4.00 eV and ~ 3.78–4.35 eV for the films grown on SLG and quartz substrates, respectively. Graphical abstract