Karuna Karan - Academia.edu (original) (raw)

Papers by Karuna Karan

Physica B: Condensed Matter, 2019

Neodymium doped zinc sulphide (Nd: ZnS) thin films were coated on glass substrates at 450 °C thro... more Neodymium doped zinc sulphide (Nd: ZnS) thin films were coated on glass substrates at 450 °C through low cost nebulizer spray pyrolysis (NSP) method. Structure, morphology, opto-electrical characteristics of Nd doped ZnS films with various Nd doping concentrations (0%, 1, %, 3% and 5%) were studied. X-ray diffraction patterns revealed that all coated films were polycrystalline hexagonal structure with (102) as a preferential direction. SEM images showed smooth and uniform spherical grains without any cracks and pinholes. Topological view by AFM described the increasing of roughness of the film through doping concentration. EDAX and Elemental mapping images confirmed the presence of Zn, S and Nd without any other impurities. Raman spectra reveals that E 1 (LO), 2TO, 2LO and 3LO emission modes with corresponding to the wave number. PL spectra showed high intense visible and broad UV emission band at 463 nm and 397 nm, respectively. Thickness of the films increased with Nd doping concentration reflecting the reduction of transparency of the films from 86% to 78% for 0% and 5% of Nd. UV-Vis Spectrum was used to study the energy gap (Eg), dielectric constant(ε), refractive index(n), and extinction coefficient (k) of the prepared films. Four-point probe method was used to calculate the activation energy of Nd: ZnS thin films from the graph drawn between ln (ρ) and (1/T).

International Journal of Scientific Research in Physics and Applied Sciences, 2019

Mn doped CdO thin films were deposited by perfume atomizer spray pyrolysis method on glass substr... more Mn doped CdO thin films were deposited by perfume atomizer spray pyrolysis method on glass substrate by varying substrate temperature (T=200 0 C, 225 0 C, 250 0 C, 275 0 C, 300 0 C). The X-ray diffraction (XRD) analysis show that the prepared cadmium oxide thin films belongs to cubic structure with preferential orientation along with (111) direction. The thicknesses of the films were determined by Stylus profiler. The average optical transmittance of the CdO films in the range of 300-800 nm, is about 58%. Estimated band gap energy (E g) is 2.65 eV and 2.5 eV. Photoluminescence (PL) spectra showed a strong emission peak around 523 nm. A systematic study on the influence of the substrate temperatures on the optical, electrical and structural properties of Mn doped CdO thin films deposited by perfume atomizer spray have been reported.

International Journal of Scientific Research in Physics and Applied Sciences, 2019

Herein we have present the preparation of Nd doped ZnS thin films on glass substrate by simple ne... more Herein we have present the preparation of Nd doped ZnS thin films on glass substrate by simple nebulizer spray pyrolysis (NSP) method at 450 0 C. XRD, SEM, and UV-Vis Spectrometer were used to analyze the Structural, morphological, and optical behavior of the prepared samples. Nature of polycrystalline hexagonal structure with no secondary phases was confirmed by X-ray analysis. Extra particle creation on the surface of the Nd doped thin film was observed in high magnified SEM images. Room temperature PL studies depicts that the luminance behavior of the parent sample was enormously changed during the Nd element interstitial with ZnS lattice. Optical band gap value varies from 3.51 eV to 3.58 eV for 3% Nd doped ZnS film ascribed the increasing of film thickness and diminishing of film transparencies.

International Journal of Scientific Research in Physics and Applied Sciences, 2019

The pure and various metals (Ni and Ba) doped Cadmium Sulphide (CdS) nano particles were successf... more The pure and various metals (Ni and Ba) doped Cadmium Sulphide (CdS) nano particles were successfully synthesized by chemical co-precipitation method using analytical grade Cadmium Chloride and Sodium Sulphide chemicals. The prepared samples were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Optical absorption (UV-Vis) studies. The XRD results showed that the all prepared samples were polycrystalline with hexagonal structure. The peaks were identified and compared with JCPDS (File No. 89-2944) values. From the SEM studies, the particles agglomerations are decreased by the addition of metal dopants and the average grain size of the particles are found in the range 500 nm. The optical properties have been characterized. The obtained band gap values are 2.56 eV, 2.54 eV, 2.35 eV and 2.48 eV. The band gap is reduced and the crystallization is increased in the Ni and Ba doped CdS nano particles are more suitable for fabrications of Opto electronic studies.

Elsevier, 2019

Neodymium doped zinc sulphide (Nd: ZnS) thin films were coated on glass substrates at 450 °C thro... more Neodymium doped zinc sulphide (Nd: ZnS) thin films were coated on glass substrates at 450 °C through low cost nebulizer spray pyrolysis (NSP) method. Structure, morphology, opto-electrical characteristics of Nd doped ZnS films with various Nd doping concentrations (0%, 1, %, 3% and 5%) were studied. X-ray diffraction patterns revealed that all coated films were polycrystalline hexagonal structure with (102) as a preferential direction. SEM images showed smooth and uniform spherical grains without any cracks and pinholes. Topological view by AFM described the increasing of roughness of the film through doping concentration. EDAX and Elemental mapping images confirmed the presence of Zn, S and Nd without any other impurities. Raman spectra reveals that E 1 (LO), 2TO, 2LO and 3LO emission modes with corresponding to the wave number. PL spectra showed high intense visible and broad UV emission band at 463 nm and 397 nm, respectively. Thickness of the films increased with Nd doping concentration reflecting the reduction of transparency of the films from 86% to 78% for 0% and 5% of Nd. UV-Vis Spectrum was used to study the energy gap (Eg), dielectric constant(ε), refractive index(n), and extinction coefficient (k) of the prepared films. Four-point probe method was used to calculate the activation energy of Nd: ZnS thin films from the graph drawn between ln (ρ) and (1/T).

The effect of negative electric field on spin-dependent tunneling in double barrier heterostructu... more The effect of negative electric field on spin-dependent tunneling in double barrier heterostructures of III
eV semiconductor is theoretically investigated. The transfer matrix approach is used by considering
Dresselhaus and induced-Rashba effect to calculate the barrier transparency and polarization efficiency.
Cent percent polarization efficiency can be achieved for the negative electric field by increasing the width
of the potential barrier. The separation between spin-up and spin-down resonances are evaluated. The
separation between spin resonances and tunneling lifetime of electrons are observed for various negative
electric fields as well as for various barrier widths. The linear variation of spin separation and tunneling
lifetime of electrons are observed as a function of negative electric field.

Materials Chemistry and Physics, Jan 1, 2001

Semiconducting nickel sulphide (NiS) thin films were deposited onto glass, fluorine doped tin oxi... more Semiconducting nickel sulphide (NiS) thin films were deposited onto glass, fluorine doped tin oxide (FTO) coated glass and single crystal Si(1 1 1) wafer substrates using a new successive ionic layer adsorption and reaction (SILAR) method. The deposition conditions for obtaining good quality films such as concentration, pH and temperature of cationic and anionic precursor solutions, immersion and rinsing times and number of immersions were optimized. The XRD studies show that the crystallinity of NiS thin films depends on the nature of substrate. The optical band gap and activation energy were found to be 0.45 and 0.15 eV, respectively. Thermo-emf measurement revealed that the films are of p-type semiconductors.

Surface & Coatings Technology, Jan 1, 2008

Transparent and conductive high preferential c-axis oriented Ni-doped ZnO (NZO) thin films as a f... more Transparent and conductive high preferential c-axis oriented Ni-doped ZnO (NZO) thin films as a function of Ni content have been prepared by sol–gel method using zinc acetate and nickel acetate as starting material, anhydrous ethanol and 2-methodxyethanol as solvent. The NZO thin films with a dopant ratio (0.2, and 0.4 mol%) have a preferred orientation in the (002) direction. However, when the Ni doping ratio exceeds 0.6 mol%, films possessed a non-textured polycrystalline structure. The electric and optical properties of the Ni doped ZnO films were found to be strongly dependent on the Ni contents. The lowest resistivity value was 4.8 × 10− 4 Ω cm, which was obtained in the 0.2 mol% Ni-doped ZnO thin film. The improvement of the electrical and optical properties of NZO films may be related to the both increase in the concentration of oxygen vacancies and free carries of Ni ions. The average optical transmittance values of the 0.2 mol% Ni-doped NZO thin films were more than 91.2% in the visible range.

Physica B: Condensed Matter, 2019

Neodymium doped zinc sulphide (Nd: ZnS) thin films were coated on glass substrates at 450 °C thro... more Neodymium doped zinc sulphide (Nd: ZnS) thin films were coated on glass substrates at 450 °C through low cost nebulizer spray pyrolysis (NSP) method. Structure, morphology, opto-electrical characteristics of Nd doped ZnS films with various Nd doping concentrations (0%, 1, %, 3% and 5%) were studied. X-ray diffraction patterns revealed that all coated films were polycrystalline hexagonal structure with (102) as a preferential direction. SEM images showed smooth and uniform spherical grains without any cracks and pinholes. Topological view by AFM described the increasing of roughness of the film through doping concentration. EDAX and Elemental mapping images confirmed the presence of Zn, S and Nd without any other impurities. Raman spectra reveals that E 1 (LO), 2TO, 2LO and 3LO emission modes with corresponding to the wave number. PL spectra showed high intense visible and broad UV emission band at 463 nm and 397 nm, respectively. Thickness of the films increased with Nd doping concentration reflecting the reduction of transparency of the films from 86% to 78% for 0% and 5% of Nd. UV-Vis Spectrum was used to study the energy gap (Eg), dielectric constant(ε), refractive index(n), and extinction coefficient (k) of the prepared films. Four-point probe method was used to calculate the activation energy of Nd: ZnS thin films from the graph drawn between ln (ρ) and (1/T).

International Journal of Scientific Research in Physics and Applied Sciences, 2019

Mn doped CdO thin films were deposited by perfume atomizer spray pyrolysis method on glass substr... more Mn doped CdO thin films were deposited by perfume atomizer spray pyrolysis method on glass substrate by varying substrate temperature (T=200 0 C, 225 0 C, 250 0 C, 275 0 C, 300 0 C). The X-ray diffraction (XRD) analysis show that the prepared cadmium oxide thin films belongs to cubic structure with preferential orientation along with (111) direction. The thicknesses of the films were determined by Stylus profiler. The average optical transmittance of the CdO films in the range of 300-800 nm, is about 58%. Estimated band gap energy (E g) is 2.65 eV and 2.5 eV. Photoluminescence (PL) spectra showed a strong emission peak around 523 nm. A systematic study on the influence of the substrate temperatures on the optical, electrical and structural properties of Mn doped CdO thin films deposited by perfume atomizer spray have been reported.

International Journal of Scientific Research in Physics and Applied Sciences, 2019

Herein we have present the preparation of Nd doped ZnS thin films on glass substrate by simple ne... more Herein we have present the preparation of Nd doped ZnS thin films on glass substrate by simple nebulizer spray pyrolysis (NSP) method at 450 0 C. XRD, SEM, and UV-Vis Spectrometer were used to analyze the Structural, morphological, and optical behavior of the prepared samples. Nature of polycrystalline hexagonal structure with no secondary phases was confirmed by X-ray analysis. Extra particle creation on the surface of the Nd doped thin film was observed in high magnified SEM images. Room temperature PL studies depicts that the luminance behavior of the parent sample was enormously changed during the Nd element interstitial with ZnS lattice. Optical band gap value varies from 3.51 eV to 3.58 eV for 3% Nd doped ZnS film ascribed the increasing of film thickness and diminishing of film transparencies.

International Journal of Scientific Research in Physics and Applied Sciences, 2019

The pure and various metals (Ni and Ba) doped Cadmium Sulphide (CdS) nano particles were successf... more The pure and various metals (Ni and Ba) doped Cadmium Sulphide (CdS) nano particles were successfully synthesized by chemical co-precipitation method using analytical grade Cadmium Chloride and Sodium Sulphide chemicals. The prepared samples were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Optical absorption (UV-Vis) studies. The XRD results showed that the all prepared samples were polycrystalline with hexagonal structure. The peaks were identified and compared with JCPDS (File No. 89-2944) values. From the SEM studies, the particles agglomerations are decreased by the addition of metal dopants and the average grain size of the particles are found in the range 500 nm. The optical properties have been characterized. The obtained band gap values are 2.56 eV, 2.54 eV, 2.35 eV and 2.48 eV. The band gap is reduced and the crystallization is increased in the Ni and Ba doped CdS nano particles are more suitable for fabrications of Opto electronic studies.

Elsevier, 2019

Neodymium doped zinc sulphide (Nd: ZnS) thin films were coated on glass substrates at 450 °C thro... more Neodymium doped zinc sulphide (Nd: ZnS) thin films were coated on glass substrates at 450 °C through low cost nebulizer spray pyrolysis (NSP) method. Structure, morphology, opto-electrical characteristics of Nd doped ZnS films with various Nd doping concentrations (0%, 1, %, 3% and 5%) were studied. X-ray diffraction patterns revealed that all coated films were polycrystalline hexagonal structure with (102) as a preferential direction. SEM images showed smooth and uniform spherical grains without any cracks and pinholes. Topological view by AFM described the increasing of roughness of the film through doping concentration. EDAX and Elemental mapping images confirmed the presence of Zn, S and Nd without any other impurities. Raman spectra reveals that E 1 (LO), 2TO, 2LO and 3LO emission modes with corresponding to the wave number. PL spectra showed high intense visible and broad UV emission band at 463 nm and 397 nm, respectively. Thickness of the films increased with Nd doping concentration reflecting the reduction of transparency of the films from 86% to 78% for 0% and 5% of Nd. UV-Vis Spectrum was used to study the energy gap (Eg), dielectric constant(ε), refractive index(n), and extinction coefficient (k) of the prepared films. Four-point probe method was used to calculate the activation energy of Nd: ZnS thin films from the graph drawn between ln (ρ) and (1/T).

The effect of negative electric field on spin-dependent tunneling in double barrier heterostructu... more The effect of negative electric field on spin-dependent tunneling in double barrier heterostructures of III
eV semiconductor is theoretically investigated. The transfer matrix approach is used by considering
Dresselhaus and induced-Rashba effect to calculate the barrier transparency and polarization efficiency.
Cent percent polarization efficiency can be achieved for the negative electric field by increasing the width
of the potential barrier. The separation between spin-up and spin-down resonances are evaluated. The
separation between spin resonances and tunneling lifetime of electrons are observed for various negative
electric fields as well as for various barrier widths. The linear variation of spin separation and tunneling
lifetime of electrons are observed as a function of negative electric field.

Materials Chemistry and Physics, Jan 1, 2001

Semiconducting nickel sulphide (NiS) thin films were deposited onto glass, fluorine doped tin oxi... more Semiconducting nickel sulphide (NiS) thin films were deposited onto glass, fluorine doped tin oxide (FTO) coated glass and single crystal Si(1 1 1) wafer substrates using a new successive ionic layer adsorption and reaction (SILAR) method. The deposition conditions for obtaining good quality films such as concentration, pH and temperature of cationic and anionic precursor solutions, immersion and rinsing times and number of immersions were optimized. The XRD studies show that the crystallinity of NiS thin films depends on the nature of substrate. The optical band gap and activation energy were found to be 0.45 and 0.15 eV, respectively. Thermo-emf measurement revealed that the films are of p-type semiconductors.

Surface & Coatings Technology, Jan 1, 2008

Transparent and conductive high preferential c-axis oriented Ni-doped ZnO (NZO) thin films as a f... more Transparent and conductive high preferential c-axis oriented Ni-doped ZnO (NZO) thin films as a function of Ni content have been prepared by sol–gel method using zinc acetate and nickel acetate as starting material, anhydrous ethanol and 2-methodxyethanol as solvent. The NZO thin films with a dopant ratio (0.2, and 0.4 mol%) have a preferred orientation in the (002) direction. However, when the Ni doping ratio exceeds 0.6 mol%, films possessed a non-textured polycrystalline structure. The electric and optical properties of the Ni doped ZnO films were found to be strongly dependent on the Ni contents. The lowest resistivity value was 4.8 × 10− 4 Ω cm, which was obtained in the 0.2 mol% Ni-doped ZnO thin film. The improvement of the electrical and optical properties of NZO films may be related to the both increase in the concentration of oxygen vacancies and free carries of Ni ions. The average optical transmittance values of the 0.2 mol% Ni-doped NZO thin films were more than 91.2% in the visible range.