Growth of tin oxide thin films composed of nanoparticles on hydrophilic and hydrophobic glass substrates by spray pyrolysis technique

In this paper, we have demonstrated the growth of tin oxide (SnO2 ) thin films composed of nanoparticles on hydrophobic (siliconized) glass and hydrophilic (non-siliconized) glass substrates by using the spray pyrolysis technique. X-ray diffraction (XRD) analysis confirmed the formation of SnO2 thin films with tetragonal rutile-phase structure. Average particle size of nanoparticles was determined to be in the range of 3-4 nm measured from the front view images obtained by a field emission gun scanning electron microscope (FESEM), while the size of nanoparticle clusters, when present, were in the range of 11-20 nm. Surface morphology of SnO2 films grown over hydrophobic substrates revealed larger isolated particles which are less crowded compared to the highly crowded and agglomerated smaller particles in films on hydrophilic substrates. Blue shift in the band gap is observed in samples in which the average particle size is slightly larger than the exciton Bohr radius (2.7 nm). Photoluminescence (PL) analysis of samples grown over hydrophobic substrates exhibited an intense defect level emission and a weak near band edge emission. The enhanced visible emission from these SnO 2 thin films is attributed to lattice defects formed during the film growth due to the mismatch between the film and the hydrophobic substrate surface.