Papers by Keyword: PL

Abstract: Cu₃SnS₄ films were grown on glass substrates via method of spin coating, followed by annealing at 550 °C in a furnace under H₂S:Ar (1:9) sulfur rates of 30 and 40 sccm for 15, 30, and 60 minutes. The effect of the sulfur rate and annealing time on the structural, morphological, and optical behaviors of the samples was systematically investigated using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), photoluminescence (PL), Hall effect, and UV-Vis spectroscopy. The XRD patterns revealed that all the Cu₃SnS₄ samples had a polycrystalline structure. The crystallite size, dislocation density, interplaner distance, micro-strain, and crystallite number of the Cu₃SnS₄ samples were calculated from the XRD spectra. Among all the samples, the CTS sample annealed for 15 minutes under a 30 sccm H₂S:Ar (1:9) gas flow showed the best crystalline structure. The surface morphology of the samples showed spherical micro-crystal formations. Analysis of the Cu₃SnS₄ samples indicated that the surfaces were composed of valley and peak regions. The valley regions appeared relatively smooth, while the peak regions displayed a crystal structure with specific orientations. When examining the energy band gap values, it is observed that the energy band gap of the films increases significantly with the increase in sulfur flow rate. PL analysis revealed emission peaks at approximately 1.41 eV and 1.80 eV, along with broad emission bands at 549 nm, 567 nm, 689.42 nm, and 882.6 nm. An increase in sulfur content led to a reduction in peak intensity, which is attributed to conduction band fluctuations and the formation of structural defects. The carrier concentration of the samples is found to be on the order of 10¹⁷ cm⁻³ and 10¹⁸ cm⁻³, which is more appropriate for thin-film solar cells (TFCSs).

Abstract: In this work, polystyrene/aluminium (PS/Al) nanocomposites were fabricated based on the various concentrations (0, 1, 5, 10, and 15 mg) of Al nanoparticles using the casting method. The resulting polymer/metal nanocomposites have good optical properties. The optical features such as transmittance and absorbance of the as-fabricated nanocomposites were investigated using the UV-Vis spectrophotometer. The effect of constriction of Al nanoparticles was noticed clearly on the transmittance and absorbance of PS/Al nanocomposites. The samples showed high absorption in the UVB range. Photoluminescence spectra (PL) revealed the UVB region of emission peak with the increasing concentration of Al NPs.

Abstract: Colloidal CdSe Nanocrystals (NCs) or quantum dots (QDs) have been developed using a yielding solution technique utilizing chemical reactions in chloroform and oleic acid in different organic solvents. This assembly is an improvement of the systematic thermal decomposition of high temperature organic solvent compounds. CdSe NCs of specific sizes can be produced easily by adjusting the solvent. This technique is reproducible and clear, so industrial development can be easily scaled up. Characterization at room temperature of the UV-Vis absorption and Photoluminescence (PL) spectra. Results reveal that the CdSe prepared with the creation of defects was nanocrystalline. The energy difference (Eg) measured in PL was 2.3 and 2.69 eV respectively for CdSe NCs in chloroform and oleic acid. The structures of the CdSe quantum dots were determined by scanning electron microscopy (SEM). The phase-transfer of chloroform and oleic acid stabilized CdSe nanocrystals solutions was studied for their potentials in white light generation applications.

Abstract: A glass system was prepared according to the formula 60mol%B₂O₃ – x mol %barite – (40-x) mol %Li₂O, where x=0, 5, 7.5, 10, 15 and 20 mol%. The amorphous nature of the prepared glasses was confirmed through X-ray diffraction. The prepared glasses were also characterized by FTIR spectroscopy, UV-vis absorption spectroscopy and the differential thermal analysis (DTA). The density is found to increase and this is because of the higher molecular of the added barite. The molar volume also increases with increasing barite content that indicates the structural changes occurred in borate network that were also confirmed using FTIR. Increasing the concentration of barite shifts the UV cutoff edge toward higher wavelengths from about 300 nm at 0 mol% barite to about 400 nm at 15 mol% of barite. Glass transition temperature (Tg) is found to increase with the increasing barite content. When analyzed by photoluminescence, the samples exhibit luminescence emission centered at around 400, 415, 480, 430, 485, 520, 545, and 570 nm when excited at 300 nm wavelength. The emission peaks at 420 nm, and 440 nm were assigned to F center emission. Between 440 nm and 520 nm it is rather the effect of the presence of the impurities.

Abstract: In this work, we have studied the crystal defectiveness and doping activation subsequent to ion implantation and post-annealing by using various techniques including photoluminescence (PL), Raman spectroscopy and transmission electron microscopy (TEM). The aim of this work was to test the effectiveness of double step annealing to reduce the density of point defects generated during the annealing of a P implanted 4H-SiC epitaxial layer. The outcome of this work evidences that neither the first 1 hour isochronal annealing at 1650 - 1700 - 1750 °C, nor the second one at 1500 °C for times between 4 hour and 14 hour were able to recover a satisfactory crystallinity of the sample and achieve dopant activations exceeding 1%.

Abstract: White color zirconia ceramics were produced by sintering of coprecipitated 3Y-TZP powder in air. By annealing at reducing atmosphere, black-color zirconia ceramics with different shades were then realized. The obtained ZrO₂ samples were characterized by X-ray diffraction (XRD), UV-visible spectrum (UV-vis), photoluminescence spectra (PL) and Raman spectroscopy, respectively. UV-visible spectrum reveals that the ZrO₂ samples under different reducing atmosphere have different reflectivity in 400-800nm. X-ray diffraction data confirms that the different annealing processes can result in the change of the corresponding crystal density. It is indicated that defects contributes to cell volume alteration. The PL and Raman spectra further indicates that these defects belong to oxygen vacancies and the concentration of oxygen vacancies have a strong influence on the shades of black-color zirconia ceramics.

Abstract: In this paper, Be-doped GaAs were grown by molecular beam epitaxy (MBE), by changing Be resource temperature, we obtained different doping concentration GaAs samples. The morphologies and electrics properties of the samples were investigated by AFM and Hall measurement. Especially, in low temperature and temperature dependent PL spectra, the Be acceptor related emission were recognized, with the doping concentration increasing, the Be acceptor related emission enhanced too.

Abstract: Mist-atomization deposition method was applied in order to grow ZnO nanostructures with various surface morphologies. ZnO was deposited from the mixture of zinc nitrate hexahydrate (Zn (NO₃)₂.6H₂O) and stabilizer, hexamethylenetetramine (HMTA, C₆H₁₂N₄) aqueous solutions onto Au-seeded glass substrate. The mixture was sprayed onto the surface of Au-seeded glass substrate at various growth temperatures of room temperature (RT), 100, 200, and 300 °C. The obtained structures were characterised by room-temperature photoluminescence (PL), field emission scanning electron microscopy (FESEM), and UV-VIS-NIR spectrophotometer. It is found that ZnO growth on 300 °C substrate temperature shows the best absorbance properties and highest UV emission peak with denser distribution amongst all. The optical and morphological properties of sprayed ZnO nanostructures largely depend on the substrates temperature during spraying the zinc nitrate solution and on the Au-seeded glass substrates.

Abstract: The polymer of poly (3-hexylthiophene) was active layer in application such as solar cells. In this paper, P3HT has been chosed to know the effect of temperature onto P3HT. The optical properties of P3HT were measured by using photoluminescence spectroscopy (PL) and UV-Vis measurement. The polymer of P3HT has been spin coated on the glass by using spin-coating method for thin films produced. The temperature was measured start at 60°C to 180 ^o C. From PL result the peak was exist at range 500-600 nm and started moved to left side when temperature increase. The UV-Vis result showed at range 400-500 nm towards to blue shifted. After heat treatment, the optical absorption spectra for the thin film of P3HT on the glass showed a distinct red-shifted with developing vibronic features of P3HT and the quenched photoluminescence (PL) spectrum was considerably restored .Keywords: P3HT; temperature; Uv-Vis; photoluminescence; PL; I-V

Abstract: Na/Mg co-doped (Na,Mg):ZnO films were fabricated on pyrex glass substrates by sol-gel spin-coating method. Effects of annealing on properties of the films were particularly investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmittance spectra. The internal stress of the films annealed at different temperature was calculated. Experimental and analytical results show that some NaCl freeze-out derivatives will appear on films when the annealing temperature is too low, with the increasing annealing temperature, the c-axis tensile stress is sharply decreased first, then the c-axis stress was changed into press stress and its value is increased continuously, so the structural, surface and the optical properties of the films improve first and deteriorate afterwards.