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RISS 인기검색어
- 검색키워드
- 저자 : Luqman Ali (검색결과 5 건)
- 무료
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Optical Characterization of a 20 Layer AlGaAs/GaAs Multiple Quantum Wells
Luqman Ali,Janghyun Cho,Clare Chisu BYEON,Jin Dong Song,조현준,Jong Su Kim 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.5
A 20-layer Al0:4Ga0:6As/GaAs multiple quantum well (MQW) sample was deposited on a GaAs substrate by using the molecular beam epitaxy (MBE) method. Optical characterization was carried out by power and temperature dependent photoluminescence (PL) for excitation powers ranging from 40 mW to 120 mW and for temperatures ranging from 11 K to 300 K. At low temperature (LT), only one dominant peak appeared in the spectrum with a much higher PL intensity and less broadening with a significant red shift ( 2:4 nm) of the peak as the excitation power was increased. As the temperature was raised to room temperature (RT), increasing excitation power linearly increased the PL with relatively no significant red shift of the main peak, which may be attributed to heavy-hole transitions near the band edge. As the temperature increased, an additional shoulder peak at higher energy are more apparent because the relative intensity of the main peak decreased. Broadening of the shoulder peak was more significant, and its full width at half maximum (FWHM) increased 4.6 nm (> 25% increase). The shoulder peak at higher energy, which is hidden under the high intensity main peak at LT, presumably indicates relative increase in light-hole transitions due to thermal transport as the temperature increases.
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Ion-Intercalation Assisted Solvothermal Synthesis and Optical Characterization of MoS2 Quantum Dots
Luqman Ali,방석재,이영중,변지수 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.2
Many of the previously reported preparation methods for MoS2 quantum dots (QDs) are limited by production rate, time consumption, tedious processes or the nal quality of the as-prepared QDs. Therefore, a simple and productive method for large-scale production of high-quality MoS2 QDs is still a challenge. We report a facile, low cost and environmentally friendly ion-intercalation assisted solvothermal route for the preparation of MoS2 QDs. In the reported method, NaOH is used as the Na+ ion source to intercalate and exfoliate the commercial MoS2 powder into nanosheets and then QDs. The reaction is carried out at a certain temperature in a Te on-lined autoclave reactor. The UV-Vis absorption spectra of the as synthesized QDs show a peak in the near UV region ( < 300 nm) instead of the characteristic peaks for the nanosheets. Characterization by X-ray diraction, atomic force microscopy and photoluminescence spectroscopy also conrmed that the as-synthesized QDs had a uniform size distribution in the range of a few nanometers with mostly a monolayer structure and showed good photoluminescence (PL) properties. The proposed method has much potential for further enhancing the yield of MoS2 QDs by taking advantage of the nature of solution-based processes.
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Mohamad Rasool Malekbala,Moonis Ali Khan,Soraya Hosseini,Luqman Chuah Abdullah,Thomas S.Y. Choong 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1
Surfactant modified carbon coated monolith was used as an adsorbent for methylene blue (MB)adsorption. Effects of pH, salt, contact time, initial dye concentrations and temperature on dyeadsorption were studied. Higher solution pH favoured MB adsorption. Furthermore, kinetics studyshowed that the adsorption could be better represented by the pseudo-second-order model. Linear andnon-linear isotherm studies revealed better fitting of Langmuir model to adsorption data with maximummonolayer adsorption capacity 388 mg/g. The adsorption was found to be spontaneous andendothermic. Desorption studies indicate that 0.1 N HCl exhibits higher elution efficiency (82.1%) withappreciable quantitative MB recovery.
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Douglas Kagoiya Ng’ang’a,Luqman Ali,이용중,변지수 한국광학회 2021 Current Optics and Photonics Vol.5 No.3
The capabilities of the near-field scanning optical microscope (NSOM) for obtaining high resolution lateral topographical images as well as for mapping the spectroscopic and optical properties of a sample below the diffraction limit of light have made it an attractive research field for most researchers dealing with optical characteristics of materials in nano scales. The apertured NSOM technique involves confining light into an aperture of sub-wavelength size and using it to illuminate a sample maintained at a distance equal to a fraction of the sub-wavelength aperture (near-field region). In this article, we present a setup for developing NSOM using a cantilever with a sub-wavelength aperture at the tip. A single laser is used for both cantilever deflection measurement and near-field sample excitation. The laser beam is focused at the apex of the cantilever where a portion of the beam is reflected and the other portion goes through the aperture and causes local near-field optical excitation of the sample, which is then raster scanned in the near-field region. The reflected beam is used for an optical beam deflection technique that yields topographical images by controlling the probe-sample in nano-distance. The fluorescence emissions signal is detected in far-field by the help of a silicon avalanche photodiode. The images obtained using this method show a good correlation between the topographical image and the mapping of the fluorescence emissions.
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Irshad Ullah,M. N. R. Baharom,H. Ahmad,B. Das,H. M. Luqman,Jawad Ali,Zainab Zainal 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.1
During the lightning activities every air terminal has the equal chances to be hit by the lightning fashes and it produce electric feld in the surrounding. Therefore, with the passage of time when the lightning air terminals become aged due to acidic rain and chemical contamination, lightning air terminal (LAT) bypasses on side edges takes place which has not been given much attention by the researchers. A modifed lightning protection system (LPS) was proposed in this paper using experimental and electromagnetic feld approach. One of the LAT on diferent geometrical structure was selected as sacrifcial point in order to reduce the chances of LAT bypasses. The modifed protection system can be referred by diferent standard to make sure buildings protection. All the experimental work was done using high voltage impulse and ANSYS/MAXWELL was used as a simulation tool. The modifed protection technique will help diferent standards to provide comprehensive protective measures against lightning.
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