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Physica
North-Holland
Physica

North-Holland

0921-4526

Physica/Journal Physica
正式出版
收录年代

    Photoluminescence and energy transfer investigations in Gd3+-Dy(3+)co-doped borate glasses

    Ullah, I.Zaman, F.Rooh, G.Khattak, S. A....
    8页
    查看更多>>摘要：We study energy transfer, Photo and X-ray luminescence in lithium barium borate glasses doped with Gd and Dy. We find that the Dy3+ luminescence at 575-nm emission wavelength increases while the Gd3+ emission at lambda em = 312 nm decreases, attributed to the energy transfer (ET) from the 6P7/2 state of Gd3+ ions to the 4F9/2 state of Dy3+ ions. From the 6P7/2 state decay lifetime (lambda exc = 275 nm and lambda em = 312 nm) of Gd3+ and that of the 4F9/2 state (lambda exc = 382 nm and lambda em = 575 nm) of the Dy3+, we compute the key parameters such as ET efficiencies, transfer probabilities and average donor-acceptor distance. Photometric parameters of the developed samples at lambda exc = 275 nm are calculated. Suggested by the Commission International deI'Eclairage coordinates, we infer that at 275-nm excitation, our optimized sample, LGBaB1.5Dy, produces white light. Measured from X-ray luminescence, the integral scintillation efficiency of LGBaB1.5Dy is 11%.
      原文链接:
    • NSTL
    • Elsevier

    One step microwave assisted synthesis of praseodymium orthoferrite nanoparticles: Rietveld refinement phase matching, optical, and magnetic property analysis

    Harikrishnan, R.Mani, G.Mani, M.Kaviyarasu, K....
    10页
    查看更多>>摘要：The formation of PrFeO3 perovskite nanocrystalline materials in the orthorhombic phase was achieved via induced exothermic heating process. The Rietveld refinement analysis performed by importing the COD database entry: 96-210-7085 in Fullprof program package has revealed that the lattice parameters of synthesized PrFeO3 unit cells are a = 5.479828 & Aring;; b = 5.578260 & Aring;; c = 7.789780 & Aring;. The crystallite size and incoherent diffraction domain induced strain of PrFeO3 are calculated as 28.24 nm and 2.4625 x 10(-4) respectively. The vacancy of Pr ion (A side) was found slightly higher than Fe ions (B-side) in the PrFeO3 unit cells. The peaks appearance at 571 cm(-1) and 536 cm(-1) due to metal oxide vibration in FTIR spectrum were assigned to harmonically vibrating (Fe-O-2 and Fe-O-5) and (Fe-O-1 and Fe-O-4) groups respectively and their vibrational frequencies agreed with the theoretically calculated frequencies. It was observed that from the MTZFC curve, rotation of the vector component (along c-axis) of Pr ion magnetic moment takes place below 35.31 K. MH hysteresis curve of prepared sample was characterized by lower magnitude of retentivity and coercivity indicating that the synthesized PrFeO3 materials fall under the category of soft ferromagnets were reported in detail.
      原文链接:
    • NSTL
    • Elsevier

    Quantum tunneling in graphene Corbino disk in a solenoid magnetic potential with wedge disclination

    Bouhlal, AhmedJellal, AhmedMansouri, Mohamed
    7页
    查看更多>>摘要：We investigate the wedge disclination effect on quantum tunneling of a Corbino disk in gapped-graphene of inner R(1 )and outer R-2 radii in the presence of magnetic flux Phi(i). We solve Dirac equation for different regions and obtain the solutions of energy spectrum in terms of Hankel functions. The asymptotic behaviors for large arguments allow us to determine the transmission, Fano factor and conductance. We establish the case where the crystal symmetry is modified locally by replacing a hexagon by pentagon, square, heptagon or octagon. We show that the wedge disclination n modifies the amplitude of transmission oscillations. We find that the period of Fano factor oscillations is of the Aharonov-Bohm type, which strongly depends on n where intense peaks are observed. As another result, n changes the minimum and period of conductance oscillations of the Aharonov-Bohm type. We show that n minimizes the effect of resonance and decreases the amplitude of conductance magnitude delta G oscillations.
      原文链接:
    • NSTL
    • Elsevier

    Modulating of electronic states and magnetic polarization in monolayered 1T-HfSe2 under non-metal atom and transition metal atom doping

    Lin, LongFeng, ZhiyanHu, ChenchengDeng, Chao...
    10页
    查看更多>>摘要：Doping is very effective in regulating the properties of two-dimensional materials. Based on the first principles of density functional theory, the effects of the electronic and magnetic properties on the 1T-HfSe(2 )monolayer with single doping of non-metallic atoms (NM) and transition metal atoms (TM) and co-doping of metal and nonmetallic atoms are systematically studied. We find that N, P and As exhibit non-magnetic metal properties. In contrast, F, Br and I exhibit magnetic semiconductor properties. The F-doped system retains the magnetic semiconductor properties under (-6%-10%) strain, and the band gap varies from 0.131 eV to 1.122 eV. Magnetic moments are generated outside the Ni atom doping system for metal atom doping. For metal and non-metal atoms doping, due to the interaction between TM and NM, found that not only can it produce massive magnetic moment and stimulate the initially did not produce a magnetic moment of non-metal atoms magnetic moment. The influence of increasing doping concentration on performance was further considered. It was found that the nearest neighbor position of the metal atom and non-metal atom was the most structurally stable, and the magnetic moment also changed when the distance between the metal atom and non-metal atom changed. These results have a specific significance for developing spintronic devices based on HfSe2.
      原文链接:
    • NSTL
    • Elsevier

    Photoelastic analysis of the clusterized 1D photonic system as a function of defect layers

    Thara, R. LakshmiPriya, P. ArunaNayak, Chittaranjan
    7页
    查看更多>>摘要：This paper demonstrates the elasto-optic behavior of the one dimensional (1D) 4-C-max clustered disordered photonic crystals. To study the effects of pressure, 2, 5, 10 and 15% of defective layers were introduced over the binary random structures. The 4-C-max clustered disordered structure is composed of polymer materials (PMMA and PS). The additional Silicon dioxide (SiO2) layers are inserted into the random system, which acts as the defect layers. The optical properties of the clustered structure under pressure are numerically calculated using the transfer matrix method. The designed wavelength, lambda is maintained at 1550 nm for optical communication purposes. When the pressure increases from 0 to 6 GPa, depending on the percentages of defective layers, there exist changes in the width of the transmission peaks. These transmission peaks appeared within the chosen spectrum (1547-1553 nm). Numerical simulations indicate the occurrences of transmission peaks with a quality factor of 775000 at 1550 nm. Moreover, the aggregated structures show the monotonic decrease of the total transmission as the function of defects and pressure. The proposed system provides a linearity scale up to 99% (i. e.R-2 = 0.99). The photoelastic properties of the 1D clustered structures are very interesting for the modelization of the filters and sensors.
      原文链接:
    • NSTL
    • Elsevier

    Structural stability, mechanical and optoelectronic properties of strain-tuned mixed-halide perovskites CsPbX3-aYa

    Yin, ShiZhang, Mao-lingChang, Jing
    9页
    查看更多>>摘要：Lead-based all-inorganic metal halide perovskites are of current interest due to their novel properties and potential applications in optoelectronic devices. Controllably strain and mixed-halide compositions are valuable way of tuning the bandgap and improve optoelectronic properties. Here, structure stability, mechanical and optoelectronic properties of strain-tuned mixed-halide CsPbX3-aYa (X, Y =I, Br, Cl; a = 0, 1, 2, 3) are investigated by first-principles calculations. Results show that their structural stability were improved with the increasing of Br or Cl doping concentration. Elastic calculations indicates that these mixed-halide CsPbX3-aYa (X, Y =I, Br, Cl; a = 0, 1, 2, 3) compounds are all mechanically stable and possess superior ductility in the studied range of pressure, which makes them suitable for thin films and flexible solar cells. Moreover, the ductility becomes more excellent as the pressure increases. Electronic properties calculations exhibit that these compounds have similar band structure. That is, they are all direct bandgap semiconductors, and the energy gap decreases with increasing pressure, and finally all structures are transformed into metallic phase. Based on the electronic structure, the optical absorption coefficients are calculated, which show that the main absorption region shifts to red light and the absorption capacity enhancement with the increase of pressure, but decreases with the increase of doping concentration of Br or Cl doping.
      原文链接:
    • NSTL
    • Elsevier

    Nonlinear optical rectification of GaAs/Al?Ga1_ ?As quantum dots system with Hulth?en-Yukawa Potential

    Chang, CengLi, XuechaoMa, Yongrui
    6页
    查看更多>>摘要：The impacts of structural parameters on the nonlinear optical rectification (NOR) coefficient in GaAs/Al eta Ga1_eta As quantum dots (QDs) with Hulthe ' n-Yukawa Potential (HYP) are explored in the reported work, including quantum dot radius, limiting potential depth, Al-concentration, hydrostatic pressure and temperature. The Nikiforov-Uvarov (N-U) method is used to solve the Schro center dot dinger equation corresponding to the restricted quantum dot system, at the same time, the subband energy level and the propagation wave function are obtained, the numerical expression of the NOR coefficient is calculated by using compact density matrix theory and iterative method. Last but not least, the results of data analysis show that these factors have an obvious influence on the nonlinear optical characteristics of the model system, it includes the change of peak value and the redshift or blueshift of coefficient formant.
      原文链接:
    • NSTL
    • Elsevier

    Anharmonic effects and EXAFS of hcp crystals studied based on high-order expanded Debye-Waller factors including dispersion effects

    Hung, Nguyen VanToan, Nguyen Cong
    7页
    查看更多>>摘要：The anharmonic effects and extended X-ray absorption fine structure (EXAFS) of hcp crystals have been studied based on the high-order expanded Debye-Waller factors. The theory is derived based on the many-body perturbation approach and cumulant expansion up to the fourth order with using the linear anharmonic oscillator model to account for the dispersion involving more contributions of phonons from the first Brillouin zone. The derived anharmonic effective potential includes the many-body effect by a simple measure avoiding the intensive full lattice dynamical calculations. The Morse potential is assumed to describe the single-pair atomic interaction. The derived analytical expressions for cumulants describe the anharmonic effects and are applied to the anharmonic EXAFS contributing to the accurate structural determination. The advantages and efficiencies of the present theory are illustrated by good agreement of numerical results for all considered quantities of Zn in hcp phase with experiment.
      原文链接:
    • NSTL
    • Elsevier

    Structural, impedance, and photoluminescence properties of Ho3+ substituted Na0.5Bi0.5TiO3

    Kumar, AbhinavRao, T. DurgaKatta, Venkata SeshaiahRaavi, Sai Santosh Kumar...
    10页
    查看更多>>摘要：Complex impedance and photoluminescence properties have been investigated in Na0.5 Bi(1-x) HoxTiO3 x = 0, 0.5, 1, 2 and 3 mol %. The observation of semicircle in the higher temperature regime from the Nyquist plots confirms the Debye type relaxation. Overlapping of normalized Z "and M " peaks suggested the long-range relaxation of charge carriers. The grain resistance (R-g) decreased with temperature. The improved insulating character was found for a small concentration (0.5 mol %) of holmium substituted NBT. Additionally, photoluminescence emission peaks associated with the transitions in Ho3+ ions were observed in the visible range. Quenching in photoluminescence intensities was observed in the higher composition (3 mol % Ho3+ substituted NBT) which we surmise as due to the collective impact of concentration quenching and the emergence of higher symmetric orthorhombic phase (Pbnm) within lower symmetric (R3c + Cc) phase.
      原文链接:
    • NSTL
    • Elsevier

    Detailed analysis of the intersubband absorption in a GaAs stepped quantum well for quadratic detection and second harmonic generation

    Salhi, WafaaSamyh, AbdelhakRajira, AmalAkabli, Hassan...
    9页
    查看更多>>摘要：We focus on intersubband transitions tunability in GaAs stepped quantum wells through the step's width variation. A double resonance can then occur due to two-photon absorption with possible promising nonlinear optics applications in absorption or emission. In this work, we identified five structures where the equidistant two photon absorption (ETPA) is possible. We have evaluated the potential of each structure for quadratic detection (QD) and/or second harmonic generation (SHG). This was accomplished quantitatively through the analysis of the calculations results of the main terms of the nonlinear factors involved in both processes. These calculations are based on those of the optical physical parameters linked to the intersubband absorption, namely the individual absorption coefficients and the corresponding dipolar momentum couplings. To highlight the enhancing effect of the asymmetry degree on the total absorption, an investigation of the optical absorption properties of symmetrical quantum wells was done in parallel.
      原文链接:
    • NSTL
    • Elsevier