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RISS 인기검색어
- 검색키워드
- 저자 : M. Dousti (검색결과 3 건)
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Ultra-fine UV Photoluminescence Emission at Room Temperature from an Individual ZnO Nanorod
A. Hadi,H. Hajghassem,M. Dousti 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.5
Highly crystalline Zinc Oxide(ZnO) nanorods and nanowires with hexagonal cross sections are grown on sputtered ZnO thin film as buffer layer, using physical vapor deposition (PVD) technique in absence of any catalyst. For experimental setup a double tubes furnace at atmospheric pressure has been utilized. The structural characteristics of samples are studied by field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and x-ray diffractometry (XRD). The optical properties of grown nanorods are investigated by micro photoluminescence (PL) spectroscopy. The results show that high quality ZnO nanostructures can be obtained by control of super saturation conditions during the growth process; while the XRD and EDS results revealed that these grown nanorods are single phase hexagonal ZnO with a perfect elemental stoichiometry. Micro PL measurement of a single nanorod results in fine spectra, in which, it exhibits a sharp ultra-violet (UV) emission bands, corresponding to near band edge (NBE) emission of crystalline ZnO, without any peak at green or orange region, which is normally related to crystal defects.
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Raja J. Amjad,M.R. Dousti,M. R. Sahar 한국물리학회 2015 Current Applied Physics Vol.15 No.1
A series of silver nanoparticles (NPs) embedded zinc-tellurite glass is prepared by melt-quenching technique. The transmission electron microscopic images reveal spherical as well as anisotropic silver NPs having average diameter in the range of 14-48 nm. The Er3+-free glass sample containing AgCl exhibits surface plasmon resonance (SPR) band of Ag NPs centered at ~ 501 nm. From Judd-Ofelt analysis, it is found that by increasing the concentration of NPs, the value of Ω2 is enhanced suggesting increased covalency and decreased symmetry around the Er3+ ions. Integrated emission cross-section (IEC) is enhanced as the concentration of silver NPs is increased up to 0.5 mol% AgCl. Fourier infrared spectra show that the intensity of the vibrational band of the water molecule and fundamental stretching band of OH group are suppressed. Furthermore, under an excitation wavelength of 786 nm, three prominent upconversion emissions are observed at 520 nm, 550 nm and 650 nm which are attributed to 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions, respectively. The upconversion emissions are enhanced significantly by introduction of silver NPs. The enhancement is mainly attributed to the local field effect of silver NPs. Studied nanocomposites are potential candidates for the development of solid state lasers.
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Asmahani Awang,S. K. Ghoshal,M. R. Sahar,M. Reza Dousti,Raja J. Amjad,Fakhra Nawaz 한국물리학회 2013 Current Applied Physics Vol.13 No.8
Glasses with composition 70TeO2e20ZnOe10Na2Oe0.5Er2O3e(x)Au are synthesized by melt-quenching technique. Their spectroscopic and optical characterizations are made. The presence of gold nanoparticles (Au NPs) with average size w9 nm is confirmed from TEM micrograph. The value of Edir is found to lie between 3.082 and 3.073 eV, while Eindir lies within 2.765 to 2.724 eV. The observed visible upconversion (UC) emission under 779 nm excitation wavelength exhibits two bands centered at 546 nm (green) and 637 nm (red) in all samples. The glass with 0.4 mol% Au NPs shows dominant enhancement in the UC emission intensity of the order of 3.5 times for the green band (4S3/2 / 4I15/2)and a weaker enhancement for the red (4F9/2 / 4I15/2) band. The optical properties of the system are affirmed to depend strongly on the Au concentration in the dielectric medium. The absorption spectra consist of six bands attributed to absorption from ground state (4I15/2) to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 2H11/2,and 4F7/2 excited states. The structural reveals that the types of bonding and difference in electronegativity can be manipulated by the presence of metallic NPs in glass matrix. JuddeOfelt analysis asserts the increase in U2 and U6 parameters with the addition of Au NPs and the enhancement of green and red emissions. The enhancement is mainly attributed to large plasmonic effect of Au NPs. The proposed glasses can be nominated as potential materials for solid state laser developments.
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