Development of strain distribution measurement method in Nano scale using Photoluminescence of Quantum Dots

在低温（10 K）下，利用水平扫描纳米探针压痕过程中的显微光致发光（PL）测量，成功地确定了量子点嵌入GaAs基体中的位置.通过引入高灵敏度的测压元件和聚焦离子束（FIB）制造的平顶纳米探针，在纳米探针水平扫描方向上的每个点上同时测量压痕力和量子点的PL，压痕力恒定。实验结果表明，量子点的发射能量与量子点相对于纳米探针的位置有很强的依赖性。因此，发射能量随着纳米探针扫描而移动，产生具有恒定压痕力的发射轨迹。基于三维有限元应变计算和应变相关的k-ε p哈密顿量相结合模拟的量子点基态的能量移动，提出了一种估计方法，使我们能够在纳米探针压痕实验中从量子点的发射轨迹中识别量子点的位置.结果表明，所有的发射痕迹清楚地观察到发射的纳米探针压痕区域的边缘周围的量子点。进一步的讨论表明，剪切应变的演变产生的空穴积累周围的接触边缘的压痕纳米探针。因此，高密度的空穴增强了该区域中的量子点的PL。

The location of quantum dots (QDs) embedded in a GaAs matrix is successfully identified by microscopic photoluminescence (PL) measurement during nanoprobe indentation with a horizontal scan at low temperature (10 K). By introducing a high-sensitive load cell and a focused ion beam (FIB)-fabricated flat-apex nanoprobe, the indentation force and PL of QDs are measured simultaneously at each point in the direction of the nanoprobe horizontal scanning with a constant indentation force. The experimental results show that the emission energy from QDs has a strong dependence on the location of QDs relative to the nanoprobe indented location. Consequently, the emission energy shifts with the nanoprobe scan, generating an emission trace with a constant indentation force. Based on the energy shift of the ground state of the QD simulated by the combination of three-dimensional finite element (FE) strain calculation and strain-dependent k〓p Hamiltonian, an estimation method is developed, which enables us to identify the location of the QD from its emission trace in the nanoprobe indentation experiment. Results indicate that all the emission traces clearly observed are emitted from the QDs around the edge of the nanoprobe-indented area. Further discussion reveals that the evolution of shear strain generates hole accumulation around the contact edge of the indented nanoprobe. Consequently, the high density of holes enhances the PL of the QDs in that region.