Papers by Keyword: Optical Property

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Authors: Anatoli Khodorov, M.J.M. Gomes
Abstract: Lanthanum modified lead zirconate titanate (PLZT) thin films were fabricated on indium doped tin oxide (ITO) - coated glass substrate by sol-gel method. The structure of the films was characterized with XRD and SEM. In the case of PLZT the dielectric function was modelled as a sum of Lorentzian oscillators and found by fitting the transmittance and reflectance spectra measured at normal incidence in the wavelength range of 220-2400 nm. The anomalous behaviour of dielectric function was observed below the absorption edge that was suggested to be due to formation of some defect states. The evolution of the absorption edge as well as dielectric function with film thickness was observed and discussed.
Authors: Jing Wen, Chun Ying Zuo, Cheng Zhong
Abstract: Motivated by the widely discussed Ag doped ZnO and the lack of follow-up reports about the realization of p-n junctions, we calculated the electronic structures and optical properties of pure, Ag-doped and Ag-F codoped ZnO based on the density-functional theory. It was found that Ag doped ZnO shows p-type conduction character. But there are some unstable factors and self-compensations in this structure. We also calcualted the formation energy and ionization energy of the impurity for Ag-F codoped ZnO. It was found that incorporating the reactive donor F into Ag doped ZnO system, not only enhances the Ag acceptor solubility, but also gets a shallower Ag acceptor energy level in the band gap. In addition, we analyze the imaginary part of the dielectric function, reflectivity and absorption coefficient for pure ZnO and Ag-F codoped ZnO. Compared with the pure ZnO, the remarkable feature for Ag-F codoped ZnO is that there is a strong absorption in the visible-light region, which indicates that it could be taken as a potential candidate for a photocatalytic material.
Authors: Hong Ju Guo, Chun Fang Wang, Jin Song Liu
Abstract: CdO nanoparticles with different sizes were synthesized by a simple thermal decomposition reaction of the precursor CdCO3, which was synthesized by room-temperature grinding reaction between Cd(CH3COO)2•2H2O and Na2CO3. Composition, structure and morphology of the products were analyzed and characterized by XRD, TG and FTIR spectra. Formation of CdO nanoparticles was thought that nucleation rate of the reactive system was far excess growth rate of particle. Optical properties of the products were recorded, and the UV-vis spectra exhibited the distinct blue shift in comparison with them of the bulk CdO, which was because that the quantum confinement effect of the products could be larger than the Coulomb effect. PL spectra of the products showed the emission bands around 520 and 720 nm respectively, which attributed to the quantum size effect and structural defects in the crystals.
Authors: Xue Jian Zhang, Chun Li, Liang Gu, Jing He Liu, Guang Tian Zou
Abstract: In this paper, the crystal growth, ceramic preparation and performance of Yb: YAG was studied systematically. The new technics that is filling protective atmosphere in the lower vacuum has been presented firstly. The Yb: YAG laser with a dimension of Φ27mm×100mm was grown by Czochralski method to medium frequency induction heating. The performance of Yb: YAG crystal was investigated by using several measurements, such as absorption spectrum, fluorescence spectrum and so on.
Authors: Stefania Privitera, Vincenza Brancato, Donatella Spadaro, Ruggero Anzalone, Alessandra Alberti, Francesco La Via
Abstract: The electrical and optical properties of n-doped polycrystalline 3C-SiC films grown on 6 inches Si wafers have been investigated as a function of precursor gases, deposition temperature and C/Si ratio. The Si/SiC interface has been optimized, eliminating the voids formation through a double temperature step process and by introducing a thin not intentionally doped layer. Films with high surface roughness, favourable for light trapping in photovoltaic applications, and with resistivity around 20 mOhm cm have been obtained for C/Si ratio close to 1. Simple solar cells have been also manufactured and proved the functionality of poly 3C-SiC/Si heterojunction solar cell. Increased quantum efficiency in the range 300-500 nm has been observed, compared to amorphous Si, making poly 3C-SiC heterojunction solar cells interesting for high temperature applications or water splitting.
Authors: Jun Ichi Hamagami, Kazuhiro Hasegawa, Kiyoshi Kanamura
Abstract: A novel micro-fabrication technique for particle assembly has been performed by an electrophoretic deposition (EPD) method using a local electric field in a colloidal suspension generated by a microelectrode. This unique EPD technique was called a “μ-EPD process”. Monodispersed polystyrene microspheres with diameters of 204, 290, and 320 nm were used in this study. A 50 μm Pt wire embedded into a polytetrafluoroethylene tube and an ITO glass slide were employed as the micro-counter electrode and the substrate, respectively. A slow deposition rate in the μ-EPD process was preferable to form a high quality micro-deposit consisting of a three-dimensional periodic polystyrene array. Under the optimized μ-EPD conditions, three-dimensionally ordered polystyrene particles were deposited in front of the micro-counter electrode. This micro-deposit constructed from polystyrene particles with a close-packed structure showed a characteristic optical absorption peak due to Bragg’s law.
Authors: Xian Qi Wei, Yong Jie Wang, Ming Yang Zhang, Zhong Zhang
Abstract: ZnO thin films are grown on sapphire substrate by employing a Nd:YAG (1064nm) laser ablation in 1.3 Pa oxygen ambient. X-ray diffraction (XRD) and atomic force microscopy (AFM) observation show that as-grown thin film possess (0002) textured feature and form columnar inclined grains with a small size. The as-grown films show a little oxygen vacancies and Zn interstitial by the analysis of X-ray photoelectron spectroscopy (XPS) and Raman. The annealing treatment in oxygen ambient causes obvious improvement on the structure, surface morphology, compositions and optical properties by the analysis of XRD, AFM, XPS, Raman and photoluminescence (PL) spectra. It can be concluded that the increase of UV emission is oriented to the improvement of structure and decrease of intrinsic defects. The blue emission (430 nm) is attributed to the electronic transition from shallow donor level of Zn interstitial to top level of valence band.
Authors: Ting Feng Tan, Yan Xia Li, Li Gang Bai, Bian Peng Wu, Hua Yan Guo, Zhi Cheng Suo
Abstract: Three aryl and three naphthylmethylene derivatives containing thiadiazole ring have been synthesized. The structures of target compounds were characterized on the basis of spectral (FT-IR, 1H NMR, and MS). The optical properties were detected using UV-vis absorption spectroscopy and fluorescence spectroscopy. The absorption spectra of 1a, 2a and 3a substituted by naphthylmethylene are primarily characterized by a peak around 284 nm originating from naphthalene, which is different from that of compounds 1b, 2b and 3b. Compared to 1a and 2a (separated by a saturable atomic cluster −CH2−), the maximum absorption wavelength of 1b and 2b takes on obvious red-shifted, which is from thiadiazole and benzene with more large conjugated system. The fluorescence intensity of 2-(4-aminobenzoyl) amide-5-naphthylmethylene-1,3,4-thiadiazole (3a) was significantly higher than that of 5-(4-aminobenzoyl)-1,3,4-thiadiazole (3b) due to the presence of naphthalene.
Authors: J.J. Ruiz-Pérez, E. Márquez, J.M. González-Leal, D. Jiménez-Garay, D. Minkov
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