Linear and Nonlinear Optics of CBD Grown Nanocrystalline F Doped CdS Thin Films for Optoelectronic Applications: An Effect of Thickness

Fluorine (F) doped (i.e. 1 wt.%) cadmium sulfide (CdS) thin films with different thicknesses were fabricated on fluorine doped tin oxide coated glass substrates by chemical bath deposition methods. For doping of F, 1 wt.% ammonium fluoride was added into the solution. A significant influence of thicknesses on physical properties of F doped CdS thin films was observed. The thin films were investigated by various characterization techniques such as x-ray diffraction (XRD), UV-Vis-NIR, FT-Raman spectroscopy and scanning electron microscope. XRD analysis showed that the films are preferentially grown along (111) plane. The crystallites' size changed with increases the film's thickness. Films showed high transmittance in visible region. Raman spectra showed shift in first and second longitudinal phonon vibration (1LO and 2LO) with the change in thickness of the films. This shows that changing thickness leads to changes in the physical properties of films. The values of the band gaps were estimated as 2.60 eV, 2.75 eV, 2.80 eV for films of thickness 100 nm, 150 nm and 200 nm, respectively. Hence, the band gap of films increases with an increase in thickness. Refractive index, linear optical susceptibility, nonlinear optical susceptibility and nonlinear refractive index were also estimated. The higher values of nonlinear optical parameters shows good scope in nonlinear optical applications.