Effect of Size and Shape on Electronic and Optical Properties of CdSe Quantum Dots

In this paper, we used the 8-band k$\cdot$p model with valence force field considerations to investigate the effect of size and shape on electronic and optical properties of cadmium selenide quantum dots. Major factors related to their properties including band mixing probabilities, spatial charge distributions, transition matrix elements and Fermi factors were studied. Volumetrically larger CdSe dots were found to have smaller band-gaps but higher transition matrix elements and Fermi factors. The maximum optical gain for dots was observed to have an initially positive and then negative correlation with their real-space size as a result of combined effects of various factors. For the shape effects, cubic dots were found to have smaller band-gaps, Fermi factors and transition matrix elements than spherical dots due to higher level of asymmetry and different surface effects. Consequently, cubic dots have lower emission energy, smaller amplification. The occurrence of near E1-H1 transition broadens the gain spectrum of cubic dots. Cubic and spherical dots are both proven to be promising candidates for optical devices under visible range. We have demonstrated that size and shape change could both effectively alter the properties of quantum dots and therefore recommend consideration of both when optimizing the performance for any desired application.Comment: Published in Optik - International Journal for Light and Electron Optics (8 pages, 10 figures), 201

Study on distribution law and influencing factors of surrounding rock plastic zone in mining roadway

By analyzing and studying the deduced theory of the surrounding plastic zone in the circular mining roadway, it is found that the radius of the surrounding plastic zone in the roadway considering the influence of mining coefficient can be divided into two stages: In the first stage, when the mining coefficient is small, the radius of the plastic zone is less sensitive to the mining coefficient, and the process increases linearly with the gradual increase of the mining coefficient. In the second stage, when the mining coefficient increases to a certain extent, the sensitivity of the radius of the plastic zone to the mining coefficient increases rapidly, and the non-linearity increases rapidly with the increase of the mining coefficient. With the gradual increase of the mining coefficient, the geometrical distribution morphology of the surrounding plastic zone of the roadway varies from circular to ellipse to round rectangle to butterfly, and the larger the mining coefficient, the more easily the surrounding rock is butterfly plastic zone, and the developmental dimension and range of the butterfly-leaf are larger. The growth of the buried depth of the roadway and the decrease of the cohesion and internal friction angle of the surrounding rock will lead to an increase in the radius of the plastic zone. With the rise of the mining coefficient, the sensitivity of the plastic zone radius to the buried depth of the roadway, cohesion and internal friction angle gradually enhanced. The butterfly plastic zone of the mining roadway has directional, and the butterfly-leaf will rotate to different degrees with the change of the principal stress direction of the surrounding rock of the roadway, When the maximum depth of butterfly-leaf plastic zone is located directly above the roof of roadway, the roof stability is the worst, and roof caving is easy to occur, thus, the support should be strengthened

1-[5-(3-Chloro­phen­yl)-2-methyl-3-thi­en­yl]-3,3,4,4,5,5-hexa­fluoro-2-(2-methoxy­phen­yl)­cyclo­pent-1-ene

The title compound, C23H15ClF6OS, has thienyl and phenyl­ene substituents on the double-bond C atoms of the envelope-shaped cyclo­pentenyl ring. The aromatic systems are aligned at 55.3 (4) (thien­yl) and 60.8 (7)° (phenyl­ene) with respect to the planar C—C=C—C portion of the main central cyclo­pentenyl ring

Optoelectronics of Inverted Type-I CdS/CdSe Core/Crown Quantum Ring

Inverted type-I heterostructure core/crown quantum rings (QRs) are quantum-efficient luminophores, whose spectral characteristics are highly tunable. Here, we study the optoelectronic properties of type-I core/crown CdS/CdSe QRs in the zincblende phase - over contrasting lateral size and crown width. For this we inspect their strain profiles, transition energies, transition matrix elements, spatial charge densities, electronic bandstructure, band-mixing probabilities, optical gain spectra, maximum optical gains and differential optical gains. Our framework uses an effective-mass envelope function theory based on the 8-band k$\cdot$p method employing the valence force field model for calculating the atomic strain distributions. The gain calculations are based on the density-matrix equation and take into consideration the excitonic effects with intraband scattering. Variations in the QR lateral size and relative widths of core and crown (ergo the composition) affect their energy levels, band-mixing probabilities, optical transition matrix elements, emission wavelengths/intensity, etc. The optical gain of QRs is also strongly dimension and composition dependent with further dependency on the injection carrier density causing band-filling effect. They also affect the maximum and differential gain at varying dimensions and compositions.Comment: Published in AIP Journal of Applied Physics (11 pages, 7 figures