Optical and structural characterization of aerosol-assisted CVD-grown Ni:ZnO thin films

The present work reports the successful growth and hence, the characterization of Ni:ZnO thin films with varying Ni contents in precursor solution ( x Ni = 0.0, 0.10, 1.00, 4.84, 9.25 and 13.27 a t . % ). The thin films were fabricated on soda lime glass substrate. An indigenously designed and developed aerosol-assisted chemical vapor deposition (AACVD) system has been used for the deposition of Ni:ZnO thin film. Zinc acetylacetonate and Nickel acetylacetonate were used as a source material for Zn and Ni, respectively. To prepare liquid precursor, isopropyl alcohol was used as a solvent for zinc acetylacetonate and Nickel acetylacetonate. The deposition was carried out at a constant growth temperature of 500 o C with oxygen as a carrier gas for the precursor. Raman spectroscopy, XRD and UV–visible spectroscopy characterizations were performed to investigate the effect of varying x Ni content over the optical as well as the structural properties of Ni:ZnO thin films. The average transmittance of undoped and Ni-doped ZnO came out to be about ≥ 95%. The calculated thickness of Ni:ZnO was found to be of the order of hundreds of nanometre i.e., the thin films of sub-micron-sized thickness have been fabricated. The measured bandgaps of Ni:ZnO thin film were found to decrease (red shift) with increasing Ni content in precursor solution. The AACVD-grown Ni:ZnO thin films was found to have low-average absorbance approximately 1% and average reflectance approximately 4%. The XRD characteristic spectra of Ni:ZnO thin films reveal that the required phase is present with a little amount of impurities that matches well with the JCPDS data indicating the hexagonal structure. The particle sizes measured by the XRD Scherer’s formula, values of lattice constants and the volume of unit cell of Ni:ZnO were found to be in a good agreement with literature. Raman spectra of pure and Ni-doped ZnO thin films have been measured at room temperature in the wave number range 150–1300 cm - 1 . A 1 (TO) modes are obtained in the range of 382–384 cm - 1 . While, the modes obtained in the ranges 569–572 cm - 1 and 1098–1104 cm - 1 are allocated as A 1 (LO) and A 1 (2LO) modes respectively.