Liu, FenhongTan, XiaojunXu, ShouleiWang, Xiangyu...
7页查看更多>>摘要：Thulium-doped yttrium aluminum garnet (YAG) single crystals with composition (TmxY(1,x))(3)Al5O12 (x = 0.001-0.02) were prepared by the optical floating zone method. The crystals were of high quality with no cracks, bubbles, or inclusions, and with >80% visible light transmittance. The lowest value for the mean positron lifetime was observed with crystals which had x = 0.01, which demonstrates that this composition had the fewest number of defects. This sample also produced the highest emission intensities in the PL spectra, and had nar-rower lines than those previously reported for Tm3+-doped yttria-stabilized zirconia. However, with higher Tm3+ concentrations, interactions between neighboring Tm3+ ions resulted in partial quenching of the luminescence. Overall, Tm-doped YAG single crystals synthesized by the optical floating zone (OFZ) method contained few defect centers and exhibited narrow luminescence linewidths, which demonstrate potential uses in high resolution applications.
原文链接:
NSTL
Elsevier
Godara, Sachin KumarSingh, MandeepKaur, VarinderNarang, S. B....
9页查看更多>>摘要：The synthesis of Sr1-xCaxFe12O19 (x = 0.0-1.0 at increments of 0.1) samples is reported via a sol-gel auto combustion process. XRD data for Sr1-xCaxFe12O19 samples calcined at different temperatures indicates a) singlephase formation up to x = 0.20 in samples calcined at 900 ?degrees C, b) an increase in calcium solubility to 50 atomic % (x = 0.50) at 1200 ?degrees C, c) a decrease in lattice parameters and cell volume with increasing 'x' and d) the presence of segregated alpha-Fe2O3 phase for x > 0.50 at 1200 ?degrees C and for x & GE; 0.20 at 900 ?degrees C. As the maximum Ca solubility in SrM (SrFe12O19) phase has been observed at 1200 ?degrees C, most of the other characterizations have been performed on these samples only. An increase in grain size with 'x' was revealed in FESEM micrographs. Magnetic measurements show that in the x = 0.50 sample the maximum saturation magnetization (M-s) value is & AP;70.67 emu/g. Coercivity (Hc) decreases monotonically, with an increase in Ca content in SrM (SrFe12O19), from 3822 Oe (x = 0.00) to 2045 Oe (x = 0.50). Among the samples calcined at different temperatures, coercivity (Hc) decreases monotonically from 5650 Oe to 3128 Oe with an increased calcination temperature for samples of x = 0.20. The samples could be vital for magnetic recording and applications as permanent magnets due to their excellent magnetic properties.
原文链接:- NSTL
- Elsevier
Sayari, A.Servatkhah, M.Pourmand, R.
6页查看更多>>摘要：The energy levels and lattice vibrational modes in quantum dots (QDs) become discrete due to 3D quantum confinement. Therefore, the influence of electron-phonon (e-p) interaction on physical properties of QDs is an important subject to study. In this work, the effects of e-p interaction and pressure in a GaAs wedge-shaped (WS) quantum dot are considered. In first step, using the dielectric continuum model, the Hamiltonian of longitudinal optical (LO) phonons and the e-p interaction Hamiltonian are analytically derived. In the next step, we have studied the e-p effect on energy eigenvalues, magnetic susceptibility and optical properties of the WS quantum dot. We have also investigated the pressure effect on optical properties of the system in the presence of the e-p interaction. It is found that the polaronic energy shift reduces when the QD size increases. The magnetic susceptibility enhances with raising the QD size. The e-p effect on magnetic susceptibility is strong for smaller QD sizes. The absorption coefficient shows two peaks in the presence of the e-p interaction. The refractive index change enhances and moves to higher energies under the e-p interaction. We found that the pressure and e-p interaction, simultaneously, have important effects on absorption coefficient and refractive index changes.
原文链接:- NSTL
- Elsevier
Ahmed, Taha YasinAbdullah, Nzar RaufGudmundsson, Vidar
7页查看更多>>摘要：Thermal transport through a Coulomb-blockade quantum dot (QD) coupled to two metallic leads is studied using five different approaches to the master equation in which sequential and coutuneling terms are taken into account. In the presence of intradot Coulomb interactions, a plateau in the thermo-particle, the heat, and the energy currents is seen. The current plateau diminishes at a high thermal bias between the leads. It is shown that the Pauli, the Redfield, the Lindblad-type equation with first order tunneling rates, and first-order von-Neumann master equations give very similar thermal transport indicating the conservation of coherency in the electron transport in sequential tunneling between the QD and leads. In contrast, the thermal transport is suppressed when coutuneling processes are taken into account via a second-order von-Neumann master equation. The consideration of second order effects with respect to the QD-leads coupling brings in a wealth of virtual processes at the contact to each lead. These virtual processes directly weaken the effects of the contribution of the first order direct processes to the overall transport, and introduce important other aspects of the transport, as level broadening, energy shifts, and lifetimes in the time-domain. As a result the current plateau formed via the Coulomb interaction diminishes, when second order and cotunneling processes are considered.
原文链接:- NSTL
- Elsevier
Kheirabadi, Sharieh JamalzadehGhayour, RahimSanaee, Maryam
8页查看更多>>摘要：Gas sensors based on Carbon Nanotube (CNT) can be used to detect harmful environmental pollutants. Also, CNT has some unique electrical properties as gas sensor application. In this research, we have presented a new structure that is constructed from joining two similar Folded Armchair Graphene Nanoribbons (FAGNRs). Two FAGNRs are joined from their open sides, which make a CNT like device with noncircular cross section and we call it Attached FAGNR tube (AFAGNT). In addition to the physical properties we have investigated gas sensing performances of CNT and AFAGNT in presence of CO, O-2 and CO2 gases molecules. In this regards, our simu-lation results of AFAGNT show different significant sensitivities to CO gas molecule at various bias voltages, especially at 0.8V. On the other hand, CO2 gas molecule doesn't adsorb onto the AFAGNT which means it is not a CO2 gas sensor.
原文链接:- NSTL
- Elsevier
Krishna, V. S. GaneshaMahesha, M. G.
14页查看更多>>摘要：Interest in the nonlinear optical properties of ZnS and the effects of alloying ZnS with other elements have been slowly increasing. Unlike ZnO, where tremendous work has been done, ZnS with similar properties is shadowed despite its prominent optical properties. Over the decade, ZnS has been successfully prepared using many techniques in its various forms such as nanoparticles, quantum dots, and thin films. Also, composite materials of ZnS have been developed to light on the enhancement in its properties. The possibility of tuning the properties of ZnS for the enhancement of nonlinear optical properties has been discussed by many reports. The suitability of ZnS for photonic device applications has been reviewed here using the Z-scan technique. Various methods of preparation, requirements, nonlinear behavior of various forms of ZnS in the past decade have been discussed in the present review article.
原文链接:- NSTL
- Elsevier
Ngantso, G. DimitriKarimou, M.Okana-Lomanga, A. L.Kadiri, A....
7页查看更多>>摘要：Based on Mean Field Theory, Exact Recursion Relations, and Monte Carlo Simulations, we have studied phase diagrams and magnetic properties of the mixed system of Ising spin-7/2 and spin-1/2 coupled ferrimagnetically. The system consists of two interpenetrating face-centered cubic sublattices of each spin type. A comparative analysis of the obtained results by these methods is developed. Our calculations have shown a qualitatively good agreement between these three methods' results. However, quantitatively, the produced output quantities values by them show a non-negligible difference. The reasons for that quantitative disagreement have been pointed out in the approximations applied in these different methods. These methods remain nevertheless power tools to study such kinds of systems.
原文链接:- NSTL
- Elsevier
Ramay, Shahid M.Ali, Syed MansoorAmer, Mabrook S.Kassim, Hamoud...
7页查看更多>>摘要：Progress of transition metal dichalcogenides for next-generation nano-photonic applications with high mobility and absorption is the main challenge in recent times. Herein, we present the first principle calculations and experimental investigations of pure and Zn incorporated MoS2 thin films. Density Functional based calculations were performed using full-potential linearized plane wave method with generalized gradient approximation as an exchange and correlation function. Pure and Zn doped MoS2 thin films were also synthesized using DC magnetron sputtering to study morphological and optical properties. A strong correlation between the electronic and optical parameters was found in the outcomes of the simulation and experimental studies. The band structure plots show significant changes in band gap values and localization of orbitals. The absorption coefficient and real epsilon were found to increase in visible regime with the incorporation of Zn reveal the practicability of these thin films for optoelectronic and dielectric applications.
原文链接:- NSTL
- Elsevier
