共查询到20条相似文献,搜索用时 15 毫秒
1.
采用线性组合算符和幺正变换方法研究磁场对非对称量子点中弱耦合束缚磁极化子性质的影响。导出量子点中弱耦合束缚磁极化子振动频率和基态能量随量子点的横向和纵向有效受限长度、库仑束缚势、磁场的回旋共振频率和电子-声子耦合强度的变化关系。数值计算结果表明:非对称量子点中弱耦合束缚磁极化子的振动频率和基态能量随量子点的横向和纵向有效受限长度的减小而迅速增大。振动频率随库仑束缚势和磁场的回旋共振频率的增加而增大。基态能量随库仑束缚势和电子-声子耦合强度的增加而减小。 相似文献
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磁场对非对称量子点中极化子性质的影响 总被引:4,自引:1,他引:3
采用线性组合算符和幺正变换方法研究磁场对非对称量子点中弱耦合磁极化子性质的影响.导出了非对称量子点中弱耦合磁极化子的振动频率、基态能量和基态结合能随量子点的横向和纵向有效受限长度、磁场和电子-声子耦合强度的变化关系.数值计算结果表明:非对称量子点中弱耦合磁极化子的基态能量和基态结合能随量子点的横向和纵向有效受限长度的增加而迅速增大.随回旋频率的增加而增大,随电子-声子耦合强度的增加而减小. 相似文献
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《Superlattices and Microstructures》1994,15(1):15
In this paper, we review our latest developments on the growth and properties of self-assembling quantum dot structures. The self-assembling growth technique which was initially developed using molecular beam epitaxy (MBE), has now been extended to metalorganic chemical vapor deposition (MOCVD). The paper first presents structural results based on atomic force and transmission electron microscopy studies of the quantum dot arrays which were obtained by MBE and MOCVD growth. From the detailed structural analysis we have observed that the formation of coherently strained dots of InAs, InAlAs, and InP dots on various cladding layer surfaces. MBE growth of InAs self-assembled dots has achieved the smallest size distribution, with dots as small as 12nm in diameter. For the MOCVD growth of InP dots we have found that the surface morphology and growth temperature of lower cladding layer growth has a profound influence on island size and density. Recent results on the optical and transport properties of the MBE grown self-assembling dot (SAD) arrays are also presented. 相似文献
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W. Nomura T. Yatsui T. Kawazoe M. Naruse M. Ohtsu 《Applied physics. B, Lasers and optics》2010,100(1):181-187
The distribution dependency of quantum dots was theoretically and experimentally investigated with respect to the basic properties
optical excitation transfer via optical near-field interactions between quantum dots. The effects of three-dimensional structure
and arraying precision of quantum dots on the signal transfer performance were analyzed. In addition, the quantum dot distribution
dependency of the signal transfer performance was experimentally evaluated by using stacked CdSe quantum dots and an optical
near-field fiber probe tip laminated with quantum dots serving as an output terminal, showing good agreement with theory.
These results demonstrate the basic properties of signal transfer via optical near-field interactions and serve as guidelines
for a nanostructure design optimized to attain the desired signal transfer performances. 相似文献
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Fanyao Qu D. R. Santos Jr. N. O. Dantas A. F. G. Monte P. C. Morais 《Physica E: Low-dimensional Systems and Nanostructures》2004,23(3-4):410
The effects of both nanocrystal shape and applied magnetic field on the electron energy spectra of colloidal ZnO quantum dots have been investigated in the frame of finite element method, using nonuniform triangular elements. Four shapes of quantum dots (spherical, ellipsoidal, rod-shaped, and lens-shaped) were studied. It was found that the physical properties of the semiconductor quantum dots could be manipulated by changing their size and/or their shape. The energies of an electron increase as one reduces the quantum dot shape symmetry from spherical towards the lens-shaped. The magnetic field effect strongly interplays with the nanocrystal size and the nanocrystal shape effects. Such interplay has been attributed to the competition of the quantum confinement effect introduced by the barrier potential and the quantum confinement effect introduced by the applied magnetic field. 相似文献
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The present study seeks to scrutinize the interactions of two electrons on the electronic properties of double ellipsoidal quantum dots (EQD). In this regard, the effective-mass approximation within a perturbation scheme is used and the Coulomb and exchange energies of the two electrons ellipsoidal quantum dot are calculated for GaAs/GaAlAs/AlAs structure. The results showed that the Coulomb and exchange energies depend not only on the thickness of the intermediate layer but also on the ellipticity constant. 相似文献
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XIE Wen-Fang 《理论物理通讯》2009,52(1):155-158
An investigation of the optical properties of a hydrogenic donor in sphericalparabolic quantum dots has been performed by using the matrix diagonalization method. The optical absorption coefficient between the ground (L=0) and the first excited state (L=1) have been examined based on the computed energies and wave functions. The results are presented as a function of the incident photon energy for the different values of the confinement strength. These results show the effects of the quantum size and the impurity on the optical absorption coefficient of a donor impurity quantum dot. 相似文献
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This article reviews the current state of research involving semiconductor quantum dots, provides a brief review of the theory behind their unique properties, and an introduction explaining the importance of quantum dot research. The characteristic shifting of the band gap energy with quantum dot size, as predicted from the density of states for low-dimensional structures, allows experimental measurements to determine the extent to which quantum confinement effects play a role in the resulting properties. A few of the current techniques used to measure the presence and physical characteristics of quantum dots and their energy levels is reviewed, including transmission electron microscopy, optical transmission, and Raman and photoluminescence spectroscopy. Finally, some of the more exciting applications for quantum dots currently being researched for use in the field of optoelectronics are reviewed, including quantum dot infrared photodetectors, quantum dot lasers, and quantum dot solar cells. Comments are made on the current progress and the future prospects of quantum dot research and device applications. 相似文献
9.
Jiang Wu Zhiming M. Wang Vitaliy G. Dorogan Yuriy I. Mazur Shibin Li Gregory J. Salamo 《Journal of nanoparticle research》2011,13(3):947-952
Self-assembled GaAs/AlGaAs quantum dot pairs (QDPs) are grown by molecular beam epitaxy using high temperature droplet epitaxy
technique. A typical QDP consists of dual-size quantum dots as observed based on atomic force microscopy image. The average
height of quantum dot is 5.7 nm for the large quantum dots and 4.6 nm for the small ones. The average peak-to-peak distance
of the two dots is about 75 nm. The optical properties of GaAs QDPs are studied by measuring excitation power-dependent and
temperature-dependent photoluminescence. Unique photoluminescence properties have been observed from both excitation power-dependent
and temperature-dependent measurements. Excitation power-dependent as well as temperature-dependent PL measurements have suggested
lateral exciton transfer in the QDPs. 相似文献
10.
XIE Wen-Fang 《理论物理通讯》2015,63(5):635-640
The absorption spectra and the refractive index changes are calculated theoretically for an exciton in a core/shell quantum dot. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The dimensionality effect of exciton quantum dots on the optical absorptions has been studied. It has been found that in the same regime, the optical absorption intensities of excitons are much smaller for the core/shell quantum dots than for the two-dimensional quantum rings. The linear and the nonlinear optical absorption coefficients and refractive index changes have been examined with the change of the confinement potential. The results show that the optical absorptions and the refractive index changes are strongly affected by the repulsive core of core/shell quantum dots. Moreover, the calculated results also reveal that as the inner radius increases, the peak values of the absorption coefficients and the refractive index changes of an exciton will show the optical Aharonov–Bohm oscillation in core/shell quantum dots. 相似文献
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In the effective mass approximation, energy eigenvalues of an electron confined in ellipsoidal and semi-ellipsoidal quantum dots, with and without hydrogenic impurity, under the influence of an external electric field have been investigated, using the matrix diagonalization method. The lower-laying states of the electron as functions of the electric field strength, the dot size and its geometry are calculated. Our results show that the electronic states are strongly affected by the applied electric field, the size and the geometry of the dot. 相似文献
15.
Engineering the spectral properties of quantum dots can be achieved by a control of the quantum dots organization on a substrate.
Indeed, many applications of quantum dots as LEDs are based on the realization of a 3D architecture of quantum dots. In this
contribution, we present a systematic study of the quantum dot organization obtained on different chemically modified substrates.
By varying the chemical affinity between the quantum dots and the substrate, the quantum dot organization is strongly modified
from the 2D monolayer to the 3D aggregates. Then the photoluminescence of the different obtained samples has been systematically
studied and correlated with the quantum dot film organization. We clearly show that the interaction between the substrate
and the quantum dot must be stronger than the quantum dot–quantum dot interaction to avoid 3D aggregation and that these organization
strongly modified the photoluminescence of the film rather than intrinsic changes of the quantum dot induced by pure surface
chemistry. 相似文献
16.
The optical properties of the populated ZnCdSe/ZnSe quantum dots have been studied by photoluminescence spectra measured with different laser excitation apertures at temperatures from 22 to 300 K. The differences of spectral features between small and large excitation spot suggest the existence of quantum dot size fluctuation in the system. The temperature evolution of photoluminescence spectral features revealed that two types of quantum dots with different densities and sizes coexist in ZnCdSe/ZnSe system. The energy spacings of the two kinds of quantum dot emissions are about 50 meV at various temperatures. The thermally activated lateral transfer processes of carriers populated in the two sorts of quantum dots are investigated by temperature dependences of spectral intensities. 相似文献
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Dipole-allowed optical absorption in a parabolic quantum dot with two electrons are studied by using the exact diagonalization techniques and the compact density-matrix approach. Numerical results are presented for typical GaAs parabolic quantum dots. The results show that the total optical absorption coefficient of two electrons in quantum dot is about five times smaller than that of one electron in quantum dot. 相似文献
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The present study seeks to scrutinize the effect of polarization charges on the electronic properties of double ellipsoidal quantum dots. In this regard, the effective-mass approximation within a variational scheme is used and the binding energy of hydrogenic impurity located at the center of ellipsoidal quantum dot (EQD) is calculated for GaAs/GaAlAs/AlAs structure. The effect of surface polarization charges due to impurity and self-polarization charges on the binding energy is considered. The results showed that the binding energy depends not only on the thickness of the intermediate layer but also on the ellipticity constant. 相似文献