c. Amirtha Kumar; R. Mohan Kumar
Abstract
Third order nonlinear optical semi-organic potassium hydrogen maleate single crystal was grown by Sangaranarayanan-Ramasamy (SR) method. The formation of the bonds in the crystal was confirmed by FTIR analysis. Thermal properties were analyzed, and found that the grown crystal is thermally stable up ...
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Third order nonlinear optical semi-organic potassium hydrogen maleate single crystal was grown by Sangaranarayanan-Ramasamy (SR) method. The formation of the bonds in the crystal was confirmed by FTIR analysis. Thermal properties were analyzed, and found that the grown crystal is thermally stable up to 196°C. The transparency (74%) was assessed from the UV-Vis studies. The photo-luminescence spectral study revealed yellow emission in the wavelength region 500-650nm. The surface laser damage threshold value of the grown crystal was measured by using Nd:YAG laser. Z-scan technique was employed to observe the third-order nonlinear optical property of the grown crystal.
P Swapna; S Venkatramana Reddy
Abstract
Pure and (Ni, Al) co-doped ZnO nanostructures are prepared lucratively by chemical co-precipitation process at room temperature by means of poly ethylene glycol (PEG) as stabilizing agent. Zinc acetate dehydrate and potassium hydroxide are used as preliminary materials. The synthesized samples are characterized ...
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Pure and (Ni, Al) co-doped ZnO nanostructures are prepared lucratively by chemical co-precipitation process at room temperature by means of poly ethylene glycol (PEG) as stabilizing agent. Zinc acetate dehydrate and potassium hydroxide are used as preliminary materials. The synthesized samples are characterized by XRD, Scanning Electron Microscopy (SEM) with EDS, Photoluminescence (PL), and Transmission Electron Microscopy (TEM). X-RAY Diffraction pattern reveals that both pristine and co-doped samples acquire hexagonal wurtzite crystal structure with no secondary phase and nonappearance of secondary phase indicates the nonexistence of impurities. SEM descriptions illustrate that all the particles are almost spherical shape and EDAX analysis reveals that doing well incorporation of dopants and lack of impurities. PL spectrum shows that all the samples containing peaks in the visible region, which will be defect related peaks. Doped samples show high intensity peaks compared with the undoped sample. TEM images reveals the nature of the particles as spherical and size of nanoparticles are confirmed the XRD data. HRTEM images plainly be evidence for nanoparticles are about 5nm with unambiguous lattice fringes. Copyright © 2018 VBRI Press.
Loreleyn F Flores; Karem Y Tucto; Jorge A Guerra; Rolf Grieseler; Jan A Töfflinger; Andres Osvet; Miroslaw Batentschuk; Roland Weingärtner
Abstract
Amorphous silicon oxycarbide (a-SiCxOy) single doped with Yb3+ and co-doped with the couple Tb3+ - Yb3+ thin films were grown on crystalline silicon substrates by rf magnetron sputtering. The elemental composition in at. % is determined by energy dispersive spectroscopy and fourier transform infrared ...
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Amorphous silicon oxycarbide (a-SiCxOy) single doped with Yb3+ and co-doped with the couple Tb3+ - Yb3+ thin films were grown on crystalline silicon substrates by rf magnetron sputtering. The elemental composition in at. % is determined by energy dispersive spectroscopy and fourier transform infrared spectroscopy allows to investigate the chemical properties of the host. The concentration of Yb in the single doped sample was 3.5% and for the codoped samples (Yb, Tb) were (3%, 0.9%), (3.5%, 0.6%) and (4%, 0.6%), respectively. Post-deposition annealing treatments were made in order to induce optical activation of the rare earths. Conversion or absorption of high energy photons were analyzed by photoluminescence spectroscopy. The photoluminescence spectra show that for a given temperature range in the thermal annealing process, as well as for the appropriate rare earth concentrations the activation of Yb3+ and Tb3+ is enhanced. A strong reduction of the Tb3+ emission in contrast to the Yb3+ emission in the a-SiCxOy,:Tb:Yb samples at annealing temperature at 500°C suggests a energy transfer from Tb3+ to Yb3+ ions. Copyright © 2018 VBRI Press.
S. Rajesh; K. Thyagarajan; Vasudeva Reddy Minnam Reddy
Abstract
Zinc Sulfide nanophosphor (ZnS) nanophosphor doped with 2 mol % Dysprosium (Dy) and co-doped with (2 – 6) mol % Manganese (Mn) was successfully prepared by cost-effective chemical co-precipitation method using polyvinylpyrrolidone (PVP) as the capping agent. The effects of dopant and co-dopant ...
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Zinc Sulfide nanophosphor (ZnS) nanophosphor doped with 2 mol % Dysprosium (Dy) and co-doped with (2 – 6) mol % Manganese (Mn) was successfully prepared by cost-effective chemical co-precipitation method using polyvinylpyrrolidone (PVP) as the capping agent. The effects of dopant and co-dopant concentrations on the various properties of ZnS were investigated by various characterizations like Powder X-ray Diffraction (PXRD) studies confirmed the cubic zinc blende structure of ZnS and no impurity peaks corresponding to Dy doping and Co-doped by Mn was observed. Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDAX) confirmed the presence of dopant Dy and co-dopants Mn in the prepared ZnS. Photoluminescence (PL) studies on Dy doped Mn and co-doped ZnS nanophosphor indicated that the emission wavelength 605 nm is tunable in the range of 400–650 nm with the incorporation of doped Dy and Co-doped Mn into ZnS host lattice with the excitation wavelength of 320 nm. Blue color of ZnS doped Dy by enhances to orange color due to co-doped with Mn ions. The chromaticity co-ordinates (CIE) and Correlated color temperature (CCT) of the phosphor were shows enhancement of blue to orange region; hence, it is useful for the fabrication of orange component of WLEDs and display applications. Copyright © 2018 VBRI Press.
Narendra Singh; Davinder Kaur
Abstract
Ultrathin silicon carbide (SiC) films were grown on p type Si (100) substrate by RF magnetron sputtering at constant substrate temperature of 7000C for investigating thickness dependence of structural and photoluminescence properties. The structural and Photoluminescence properties were measured by X-ray ...
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Ultrathin silicon carbide (SiC) films were grown on p type Si (100) substrate by RF magnetron sputtering at constant substrate temperature of 7000C for investigating thickness dependence of structural and photoluminescence properties. The structural and Photoluminescence properties were measured by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and photospectrometer respectively. X-ray diffraction pattern revealed (102) and dominant (105) reflections which corresponds to 4H-SiC and an enhancement in (105) peak intensity with increasing thickness was also observed. The thickness measured by X-ray reflectometry (XRR) reduces from ~ 46 nm to 12 nm by decreasing deposition time (40-10 minute) which in turn reduces the crystallite size. Photoluminescence spectra show a broad peak extending from ultraviolet to blue region centered at ~ 385 nm for film of thickness ~ 46 nm (deposition time 40 min). A shifting in Photoluminescence peak towards shorter wavelength (blue shift) with decreasing SiC ultrathin film thickness was observed, which could be attributed to quantum confinement effect. The improved Photoluminescence in ultrathin nanocrystalline SiC films could make it a potential candidate in optoelectronic and biomedical applications. Copyright © 2017 VBRI Press.
Bhawana Joshi; Santanu Ghosh; Pankaj Srivastava
Abstract
In the present work, ZnO thin films deposited by pulsed laser deposition (PLD) technique have been characterized structurally and optically after post-deposition annealing. As-deposited thin films were annealed in the ambient atmosphere for different annealing temperatures of 2000C, 4000C, 6000C and ...
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In the present work, ZnO thin films deposited by pulsed laser deposition (PLD) technique have been characterized structurally and optically after post-deposition annealing. As-deposited thin films were annealed in the ambient atmosphere for different annealing temperatures of 2000C, 4000C, 6000C and 8000C. X-ray diffraction (XRD) technique was used for structure analysis and elucidated that both as-deposited and annealed films were of good structural quality and highly oriented towards c-axis. UV-Vis spectrophotometer was used to study the transmittance and optical band gap of as-deposited and annealed films. Photoluminescence (PL) technique was used to investigate the photoluminescent properties of all the films. It was found that ZnO thin films were highly transparent in nature and showed two emissions in PL spectra. One was attributed to near band edge (NBE) emission and the other was the broad deep-level (DL) emission. There was a significant change in the photoluminescent properties of the films and it was observed that the intensity of the DL emission increased significantly with the increase in the annealing temperature. The change in DL emission is attributed to the change in defect states inside the band gap of the annealed films. From the present work, it is inferred that the properties of the ZnO films can be tuned by post-deposition annealing for various applications such as optical and optoelectronic devices. Copyright © 2017 VBRI Press.
Sarika Singh; A.K. Shrivastava; Swati Tapdiya
Abstract
Cadmium Selenide (CdSe) doped with (Mn) Manganese Chloride grown, on commercial glass substrate usingChemical Bath Deposition Method. Growth time was kept at 1-2 hours. Magnese Chloride (Mncl2) was used for dopant. CdMnSe films so obtained were characterized using X-Ray Diffraction, Scanning Electron ...
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Cadmium Selenide (CdSe) doped with (Mn) Manganese Chloride grown, on commercial glass substrate usingChemical Bath Deposition Method. Growth time was kept at 1-2 hours. Magnese Chloride (Mncl2) was used for dopant. CdMnSe films so obtained were characterized using X-Ray Diffraction, Scanning Electron Microscopy, EdAX, andUV-Visible spectrophotometer and photoluminescence studies respectively. XRD study confirms that CdSe films are polycrystalline in nature and have cubic structure. The Debye-Scherer formula was used to calculate average particle size of pure and doped CdSe film. Thus, the particle size was decrease on doping. The effect of doping concentration Mn on the luminescence spectra of CdSe was studied. The emission spectra revealed that the intensity increased considerably in the presence of dopant ions. It is clearly observed from the surface morphological studies by SEM that the as-deposited CdSe and doped Mn concentration films are nanocrystalline, homogenous, without cracks or holes and well covered to the glass substrate. FE-SEM images show spherical particles having uniform distribution. Roughness of the films were totally eliminated. EDAX patterns confirms the presence of Cadmium, Selenide and Magnese chloride elements (2%, 5%)in sample. Optical band gap of pure CdSe film comes out to be 2.1 eV.After doping energy band gap was decreasing. Copyright © 2017 VBRI Press.
Nidhi Gupta; Rakhi Grover; Dalip S. Mehta; Kanchan Saxena
Abstract
Here we present fabrication of one dimensional photonic band gap structure (1D-PBG) based on periodic layers of silver and magnesium fluoride (MgF2) for tuning the emission of polyfluorene derivative, Poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO). Transmittance measurements were used to characterize the ...
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Here we present fabrication of one dimensional photonic band gap structure (1D-PBG) based on periodic layers of silver and magnesium fluoride (MgF2) for tuning the emission of polyfluorene derivative, Poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO). Transmittance measurements were used to characterize the photonic band gap. 1D-PBG structure with varying thickness of silver was fabricated on the back side of PFO coated glass substrate. Photoluminescence studies confirmed that blue emission was enhanced while the secondary peaks were suppressed. Photoluminescence spectra shows that the blue to green peak intensity ratio was improved by 1.7 times approximately with PBG. These type of PBG structures can be used to enhance the color purity of PFO based blue organic light emitting diodes. Copyright © 2017 VBRI Press.
J. Dhanalakshmi; D. Pathinettam Padiyan
Abstract
GdxTi1-xO2 nanocomposites with x=0.00, 0.02, 0.04, 0.06, 0.08 & 0.10 were prepared through sol-gel method. The samples were characterized using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), High resolution scanning electron microscope (HR-SEM), Raman spectroscopy and photoluminescence ...
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GdxTi1-xO2 nanocomposites with x=0.00, 0.02, 0.04, 0.06, 0.08 & 0.10 were prepared through sol-gel method. The samples were characterized using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), High resolution scanning electron microscope (HR-SEM), Raman spectroscopy and photoluminescence spectroscopy (PL). The XRD pattern and Raman spectra confirmed the presence of crystalline nature and phase pure anatase tetragonal system. The average crystallite size of the samples was between 10 to 18 nm. HR-SEM images indicated the formation of spherical like particles of GdxTi1-xO2 nanocomposites. An obvious reduction in particle size of GdxTi1-xO2 nanocomposites were noticed while comparing the SEM images of bare TiO2 and composite samples. Coupling of Gd is responsible for slight blue shift in absorption edge. The presence of oxygen vacancies is confirmed in Raman and PL spectra. These oxygen vacancies potentially trap electrons and restrict the electron-hole recombination and thus improve the photocatalytic reactions.
