CHARACTERIZATIONS OF SnO2 THIN FILMS PREPARED USING SOL-GEL METHOD
Abstract
The aim of this project is to investigate the effect of annealing process on the structural, morphological and optical properties on SnO2 thin film. A chloride-based inorganic sol gel route was used for preparing pure SnO2 sol. SnCl4 as a precursor was first reacted with propanol and then the resulting compound was hydrolyzed. The obtained sols were used for depositing thin films by spin coating technique or for preparing powder by solvent evaporation at 100°C followed by annealing at 500°C and 600°C for 4 hours. Structural investigation using XRD revealed that unannealed SnO2 powder exhibited an amorphous structure while the crystalline peaks of SnO2 powder at both 500°C and 600°C corresponds to the tetragonal crystallographic structure (cassiterite). The annealed SnO2 film showed rough surface with porous structure and small grains. However, no grain boundary observed in as-deposited SnO2 thin film. TEM analysis showed that the crystallized SnO2 particles exist as round grains with size varies between 15-50 nm range. The optical measurement revealed the annealing process significantly reduced the optical band gap, Eg with from 3.93 eV in as-deposited film to 3.86 eV after annealing.
