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

Sn_0.96?xLa_0.04Cu_xO₂ (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 Sn_0.97La_0.02Cu_0.01O₂ nanocrystals seems to be optimal for industrial applications especially as transparent electrode. The initial blue shift of energy gap from 3.65 eV (Cu = 0%) to 3.78 eV (Cu = 1%) (ΔE_g ≈ 0.13 eV) 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 686 cm^?1 in Sn_0.98La_0.02O₂ nanocrystals and anti-symmetric SnOSn stretching mode of the surface bridging oxide around 634–642 cm^?1 in Cu doped Sn_0.98La_0.02O₂ nanocrystals was confirmed by Fourier transform infrared spectra.