Facilely fabricated Sr@NiO/FTO films and their characterizations for opto-nonlinear applications

Nickel oxide (NiO) is found to have several fascinating applications in optoelectronics and spintronic devices. Hence, herein we facilely fabricated the NiO thin films with 0.0, 1.0, 2.5 and 5.0 wt.% Sr doping by low-cost spin coater at RT. The single-phase confirmation of Sr@NiO films was done by X-ray diffraction and FT-Raman analyses. The crystallite size was estimated through Scherrer rule and noted to lie between 13 to 31 nm. The broad Raman peaks indicate low dimension nanostructured films formation. Sr doping in NiO was detected by EDX spectra and its homogeneity in final film by SEM e-mapping. AFM analysis revealed nano-spherical grains in all films. The grown films were tested for optical transparency and noticed that the films are transparent viz. ~ 45 to 65% over 500 to 1400 nm wavelength region. The direct energy gap and refractive index was determined and lies between 3.74 to 3.84 eV and 1.6 and 2.2 in the visible, correspondingly. The values of dielectric constant were calculated in range from 2 to 60. The linear, third order nonlinear and nonlinear refractive index values are noted to be enhanced by Sr content in energy range from 1 to 4 eV. The enhanced energy gap and nonlinear activities signify the importance of the grown Sr@NiO films for optoelectronics.