Department of Opto-Mechatronics Engineering and Cogno-Mechatronics Engineering, Physics Education, RCDAMP, Pusan Nat'l University, Busan 609-735, Republic of Korea.
Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU, U.K.
Sci Rep. 2017 Jan 5;7:40026. doi: 10.1038/srep40026.
Generally confinement size is considered to determine the dimensionality of nanostructures. While the exciton Bohr radius is used as a criterion to define either weak or strong confinement in optical experiments, the binding energy of confined excitons is difficult to measure experimentally. One alternative is to use the temperature dependence of the radiative recombination time, which has been employed previously in quantum wells and quantum wires. A one-dimensional loop structure is often assumed to model quantum rings, but this approximation ceases to be valid when the rim width becomes comparable to the ring radius. We have evaluated the density of states in a single quantum ring by measuring the temperature dependence of the radiative recombination of excitons, where the photoluminescence decay time as a function of temperature was calibrated by using the low temperature integrated intensity and linewidth. We conclude that the quasi-continuous finely-spaced levels arising from the rotation energy give rise to a quasi-one-dimensional density of states, as long as the confined exciton is allowed to rotate around the opening of the anisotropic ring structure, which has a finite rim width.
通常认为限制大小决定了纳米结构的维度。虽然激子玻尔半径被用作光学实验中定义弱或强限制的标准，但束缚激子的结合能很难通过实验测量。一种替代方法是使用辐射复合时间的温度依赖性，这在量子阱和量子线中已经得到了应用。通常采用一维环结构来模拟量子环，但当边缘宽度与环半径相当时，这种近似就不再适用。我们通过测量激子的辐射复合的温度依赖性来评估单个量子环中的态密度，其中通过使用低温积分强度和线宽来校准光致发光衰减时间作为温度的函数。我们得出结论，只要允许束缚激子围绕各向异性环结构的开口旋转，该开口具有有限的边缘宽度，那么由旋转能量产生的准连续精细间隔能级就会导致准一维态密度。
