Strain distributions and electronic structure of three-dimensional InAs/GaAs quantum rings

This paper presents a finite element calculation for the electronic structure and strain distribution of self-organized InAs/GaAs quantum rings. The strain distribution calculations are based on the continuum elastic theory. An ideal three-dimensional circular quantum ring model is adopted in this work. The electron and heavy-hole energy levels of the InAs/GaAs quantum rings are calculated by solving the three-dimensional effective mass Schr?dinger equation including the deformation potential and piezoelectric potential up to the second order induced by the strain. The calculated results show the importance of strain and piezoelectric effects, and these effects should be taken into consideration in analysis of the optoelectronic characteristics of strain quantum rings.     

应变补偿层对量子点生长影响的理论研究

量子点的光学特性与量子点的大小均匀性、密度、内部应变以及隔离层的厚度等有密切关系.文中从理论角度定量研究了GaNXAs1-X应变补偿层对InAs/GaAs量子点生长质量的改善作用,分析了应变补偿层对隔离层厚度减小的作用.讨论了应变补偿层的补偿位置和补偿层N组分X对量子点生长时局部应变和体系应变的补偿作用.分析了应变补偿层对体系应变的减少作用,并计算了相邻层量子点的垂直对准概率.研究结果对实验中应变补偿的优化和高质量量子点阵列的生长实现提供了理论依据.     

Electronic and optical properties of GaN/AlN quantum dots with adjacent threading dislocations

We present a theory to simulate a coherent GaN QD with an adjacent pure edge threading dislocation by using a finite element method. The piezoelectric effects and the strain modified band edges are investigated in the framework of multi-band $\bm k\cdot \bm p$ theory to calculate the electron and the heavy hole energy levels. The linear optical absorption coefficients corresponding to the interband ground state transition are obtained via the density matrix approach and perturbation expansion method. The results indicate that the strain distribution of the threading dislocation affects the electronic structure. Moreover, the ground state transition behaviour is also influenced by the position of the adjacent threading dislocation.     

表面接枝亲水性聚合物刷磁性微球的制备及其对蜂蜜中四环素类抗生素残留的磁分散固相萃取

采用电子转移活化再生催化剂原子转移自由基聚合法（ARGET-ATRP）在磁性微球（MMs）表面连续接枝了聚碱类聚合物和聚乙二醇刷。首先将MMs包覆硅胶,接枝氨基,然后在其表面接枝溴引发剂,最后在MMs表面进行聚合,制备了亲水性聚合物刷磁性微球（HMMs）。通过透射电镜、傅里叶变换红外光谱对HMMs进行表征,并研究了HMMs对蛋白质的吸附性能。结果表明,合成的HMMs粒径较为均一,分散性良好并且具有良好的抗蛋白质吸附性能。利用制备的HMMs,采用磁分散固相萃取（MDSPE）-高效液相色谱法（HPLC）测定了蜂蜜中四环素类抗生素（TCs）残留。TCs的平均回收率为85.8%~94.5%,方法的检出限和定量限分别为1.92~2.56 μg/kg和6.40~8.53 μg/kg。该方法成功地用于蜂蜜中TCs残留的快速分离富集。