We investigated the valley Zeeman splitting of excitonic peaks in the microphotoluminescence (μPL) spectra of high-quality hBN/WS2/MoSe2/hBN heterostructures under perpendicular magnetic fields up to ...20 T. We identify two neutral exciton peaks in the μPL spectra; the lower-energy peak exhibits a reduced g-factor relative to that of the higher energy peak and much lower than the recently reported values for interlayer excitons in other van der Waals (vdW) heterostructures. We provide evidence that such a discernible g-factor stems from the spatial confinement of the exciton in the potential landscape created by the moiré pattern due to lattice mismatch or interlayer twist in heterobilayers. This renders magneto-μPL an important tool to reach a deeper understanding of the effect of moiré patterns on excitonic confinement in vdW heterostructures.
We report a comprehensive discussion of quantum interference effects due to the finite structure of neutral excitons in quantum rings and their first experimental corroboration observed in the ...optical recombinations. The signatures of built-in electric fields and temperature on quantum interference are demonstrated by theoretical models that describe the modulation of the interference pattern and confirmed by complementary experimental procedures.
In this paper, we report on structural and optical properties of terbium and europium doped barium stannate phosphors (BaSnO3) synthesised by conventional solid state reaction method. We have studied ...those materials by using X-ray diffraction (XRD), radioluminescence (RL) and photoluminescence (PL) techniques. XRD patterns confirm that the BaSnO3 sintered at 1400°C exhibit orthorhombic structure and that the Tb3+ and Eu3+ substitution of Ba2+ does not change the structure of the BaSnO3 host. The optical emission spectrum is characterized a broad band centered at 897nm (1.38eV), with a high-energy tail approximately 750nm from the host lattice. Other emission signals that are characteristic of the 3+oxidation state of rare earth elements were generated by Eu and Tb doping. Luminescence measurements show that the series of emission states 5D4→7F6, 5D4→7F5, 5D4→7F4 and 5D4→7F3 corresponding to the typical 4f→4f infra-configuration forbidden transitions of Tb3+ are appeared and the major emission peak at 540nm is due to 5D4→7F5 transitions of Tb3+. On the other hand, the emission spectrum of Eu doped BaSnO3 phosphor exhibits a series of emission bands, which are attributed to the 5D0→7Fj (j=0–4) transitions of Eu3+ ions. The dominant emission of Eu3+corresponding to the electric dipole transition5D0→7F2is located at 613nm. The sharp emission properties exhibited demonstrate that the BaSnO3 is a suitable host for rare-earth ion doped phosphor material. This work clearly confirms the unusual near infrared (NIR) PL discovered by H. Mizoguchi et al. in BaSnO3 at room temperature.
We have investigated the electrical and optical properties of erbium (Er
3+
) doped TiO
2
thin films (Er:TiO
2
TFs) grown by sol–gel technique on glass and silicon substrates. The samples were ...characterized by field emission gun–scanning electron microscopes (FEG–SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), X-ray diffraction (XRD), photoluminescence (PL) and current–voltage measurement techniques. FEG–SEM and AFM images showed the morphological change in the structure of Er:TiO
2
TFs and EDX analysis confirmed the Er
3+
doped into TiO
2
lattice. Broad PL emissions in visible and infrared regions were observed in undoped TiO
2
samples and associated to different mechanisms due to the anatase and rutile phases. PL spectra revealed sharp peaks at 525 nm, 565 nm, 667 nm and 1.54 µm which are related to Er
3+
emissions in Er:TiO
2
samples. The undoped TiO
2
and Er:TiO
2
TFs based UV-photodetectors were fabricated, and various device parameters were investigated. The doped devices exhibit high photoresponse upon illuminating 350 nm UV light at 2 V bias with faster response time compared to undoped device.
Extensive work on InAs quantum dots grown on GaAs substrates has been reported in the literature. However, research in the use of different substrate materials such as silicon to achieve an ideal and ...full integration of photonic and electronic systems is still a challenge. In this work we have investigated the effect of the substrate material (Si and GaAs) and strain reducing layer on the optical properties of InAs quantum dots for possible applications in laser devices grown by Molecular Beam Epitaxy. Two InAs quantum dots structures with similar active regions grown on GaAs and Si substrates using strain reducing layer consisting of InAs QDs/6 nm In0.15Ga0.85As have been investigated. Atomic Force Microscopy, Transmission Electron Microscopy, and photoluminescence have been used for the characterization of the samples. We have observed a red shift of the InAs QD photoluminescence peak energy for the sample grown on Si substrate as compared to the sample grown on GaAs substrate, which was associated with residual biaxial strain from the Si/GaAs heterointerface. This red-shift of the photoluminescence peak energy is accompanied by a broadening of the photoluminescence spectrum from ∼31 meV to a value of ∼46 meV. This broadening is attributed to the quantum dots size inhomogeneity increase for samples grown on Si substrate. This result open new insights for the controlling the emission of InAs quantum dots for photonic devices integration using Si substrates.
•Strain relaxation layer.•Indium arsenide.•Quantum dots.•Silicon integration.•Photoluminescence.
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