Faculty Publications
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Item The role of cobalt doping in tuning the band gap, surface morphology and third-order optical nonlinearities of ZnO nanostructures for NLO device applications(Royal Society of Chemistry, 2019) Bairy, R.; Patil, P.S.; Maidur, S.R.; Vijeth, H.; Murari, M.S.; Bhat K, U.K.The work presented here reported the effect of doping cobalt (Co) in ZnO thin films. The thin films were prepared using the spray pyrolysis technique with 0, 1, 5 and 10 wt% cobalt doping concentrations to study the morphological, optical and third-order nonlinear optical (NLO) properties. X-ray diffraction revealed the crystalline nature of the prepared thin films, and the crystallite size was found to increase with the concentration of doped Co. The morphology and surface topography of the films were largely influenced by doping, as indicated by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). With an increase in Co-doping concentration, the direct optical energy band-gap value increased from 3.21 eV to 3.45 eV for pure to 10 at% of Co concentrations respectively. To study the NLO properties of the prepared thin films, the Z-scan technique was adopted; it was observed that with an increase in the doping concentration from 0 to 10 wt%, the nonlinear absorption coefficient (?) was enhanced from 4.68 × 10-3 to 9.92 × 10-3 (cm W-1), the nonlinear refractive index (n2) increased from 1.37 × 10-8 to 2.90 × 10-8 (cm2 W-1), and the third-order NLO susceptibility (?(3)) values also increased from 0.79 × 10-6 to 1.88 × 10-6 (esu). At the experimental wavelength, the optical limiting (OL) features of the prepared films were explored, and the limiting thresholds were calculated. The encouraging results of the NLO studies suggest that the Co:ZnO thin film is a capable and promising material for nonlinear optical devices and optical power limiting applications. © 2019 The Royal Society of Chemistry.Item Investigation of third-order nonlinear optical properties of nanostructured Ni-doped CdS thin films under continuous wave laser illumination(Springer, 2019) Bairy, R.; Arasalike, A.; Shivakumar, G.K.; Radhakrishnan, K.; Bhat K, U.K.We report the third-order nonlinear optical (NLO) properties and optical limiting (OL) thresholds of pure CdS and Ni-doped CdS thin films have been investigated with the Z-scan technique under continuous wave laser excitation. Nanocrystalline CdS thin films with various doping concentrations of Ni (0%, 1%, 3%, 5% and 10 at. %) are prepared by spray-pyrolysis technique. XRD patterns reveal that all the prepared films are polycrystalline and the incorporation of Ni does not lead to major changes in the crystalline phase of Cd1-xNixS thin films. The surface morphology of the prepared films is impacted by the Ni-doping and is indicated by Field Emission Scanning Electron Microscopy (FESEM) images. With an increase in Ni-doping concentration, the energy band-gap value decreased from 2.48 eV to 2.23 eV. From the Z-scan data, it is observed that the material show strong two-photon absorption (2PA) and with an increase in Ni-doping concentrations from 0 to 10 at. %, the nonlinear absorption coefficient (?) are enhanced from 0.92 x 10-5 to 4.46 x 10-5 (cm W-1), nonlinear refractive index (n2) from 0.2967 x 10-9 to 0.1297 x 10-8 (cm2 W-1) and thereby the third-order NLO susceptibility (?(3)) values also increased from 1.7075 x 10-6 to 7.4743 x 10-6 (esu). OL characteristics of the prepared films are studied at the experimental wavelength. The results propose that the Cd1-xNixS film is a capable material for nonlinear optical devices at 532 nm and optical power limiting applications. © Springer Science+Business Media, LLC, part of Springer Nature 2019.Item A systematic investigation on structural, electrical, linear and nonlinear optical properties of Zn:CdO thin films for optoelectronic applications(Elsevier B.V., 2021) Nagaraja, B.S.; Gurumurthy, S.C.; Bairy, R.; Koduri, K.; K, B.; Rao, A.In the present work, a systematic study on structural, electrical, linear, and nonlinear optical properties of Zn doped CdO thin films prepared by Spray Pyrolysis (SP) technique is reported. X-ray diffraction (XRD) studies revealed the cubic, wurtzite structure, and polycrystalline nature of all the films. The observed results showed a decrease in lattice constant and unit cell volume with an increase in Zn doping concentration. Morphology study confirms uniform distribution of spherical grain-like structure with small voids. An increase in direct and indirect bandgap is observed with doping concentration up to 5 wt%, and the trend reverses at higher concentration. The significant effect of Zn doping on optical parameters such as absorption coefficient, extension coefficient, refractive index, optical dielectric constant, and optical conductivities are calculated for all thin films. Further, the optical studies were used to analyze the linear susceptibility, third-order nonlinear optical susceptibility, and nonlinear refractive index of the films. The observed values for ?(1),?(3) and n2 are in the range from 0.03 to 0.09 esu, 3.51×10?16 to 1.02×10?14 esu, and 1.09×10?14 to 2.67×10?13 esu for pure and Zn doped thin films respectively. Hall coefficient and electrical studies indicate that the Zn doping influences the electrical properties. An n-type and ohmic behavior is also observed for these films. Optical and electrical results suggest that these Zn:CdO films can be a potential candidate for optoelectronic applications. © 2021 Elsevier B.V.Item Improvement of third-order NLO properties of vacuum deposited Cd1-xPbxS nanostructured thin films for optoelectronic device applications(Elsevier Ltd, 2023) Bairy, R.; Vijeth, H.; Kulkarni, S.D.; Murari, M.S.; Bhat K, U.K.A polycrystalline nanostructured cadmium lead sulfide thin film was deposited using the thermal evaporation (PVD) technique (Cd1-xPbxS with x = 0.00, 0.01, 0.05 and 0.1 wt.% of Pb). Structural parameters of as-prepared Cd1-xPbxS thin films have been studied through X-ray diffraction. The optical investigation demonstrates that Cd1-xPbxS film's optical band gap (Eg) may be adjusted from the visible to the near-infrared region. (2.64 - 2.42 eV). The film is substantially more appropriate for absorbing layers in solar cells and optoelectronic applications due to the large decrease in ‘Eg.’ The enhanced Pb doping was found to have altered the surface morphology, verified by Field Emission Scanning Electron Microscopy (FESEM) images. The doped films also showed a significant red shift in the band edge and increased transmittance in the visible and NIR regions. The third-order nonlinear optical (TONLO) parameters of the samples were determined from the Q-switched Nd: YAG laser with 65-ps pulse duration at 1064 nm. The investigated TONLO components such as nonlinear absorption coefficient (β), nonlinear refractive index (n2) and the susceptibility χ(3)were found to be in the range from 1.16 × 10−3 to 4.12 × 10−3 (cmW−1), 1.06 × 10−8 to 3.32 × 10−8 (cm2 W−1) and 1.23 × 10−4 to 5.62 × 10−4 (esu) respectively. The results indicate that Pb-doping on CdS nanostructures on surface morphology can be used to modify NLO characteristics.Cd1-xPbxS thin film is a potential and able material for optoelectronic device applications, as seen by these encouraging NLO results. © 2023 Elsevier Ltd