Structural, optical and morphological properties of La, Cu co-doped SnO2 nanocrystals by co-precipitation method

Abstract

Sn0.96−xLa0.04CuxO2 (0⩽x⩽0.03) nanocrystals have been successfully synthesized by employing a simple co-precipitation method. The crystal structure of the synthesized nanocrystals was found to be tetragonal rutile of tin oxide by using X-ray diffraction technique and was not affected by doping. The change in lattice parameters was discussed based on the secondary phase formation and presence of Cu2+/Cu3+ in LaSnO2 lattice. The variation in size and shape of the nanocrystals by Cu-doping was discussed using scanning electron microscope. The chemical stoichiometry of Sn, Cu, La and O was confirmed by energy dispersive X-ray spectra. The best optical transparency and lower absorption observed at Sn0.97La0.02Cu0.01O2 nanocrystals seems to be optimal for industrial applications especially as transparent electrode. The initial blue shift of energy gap from 3.65eV (Cu=0%) to 3.78eV (Cu=1%) (ΔEg≈0.13eV) is due to the distortion in the crystal structure of the host compound and generation of defects. The red shift of energy gap after Cu=1% is due to the charge-transfer transitions between the metal ions d-electrons and the SnO2 conduction or valence band. Lattice mode of SnO2 at 686cm−1 in Sn0.98La0.02O2 nanocrystals and anti-symmetric SnOSn stretching mode of the surface bridging oxide around 634–642cm−1 in Cu doped Sn0.98La0.02O2 nanocrystals was confirmed by Fourier transform infrared spectra.