Xu Lixia, Arai Yoshio, Ozasa Kazunari, Kakoi Hiroki, Liang Yuan-Hua, Araki Wakako
Graduate School of Science and Engineering, Saitama University, 255 Shimo-Ohkubo, Sakura-ku, Saitama 338-0825, Japan.
J Nanosci Nanotechnol. 2011 Jan;11(1):106-14. doi: 10.1166/jnn.2011.3818.
The low-temperature (10 K) photoluminescence (PL) of self-assembled InGaAs/GaAs quantum dots (QDs) was measured under the elastic indentation of a flat cylindrical nanoprobe that generates localized strain fields around itself. As the indentation force increases, the intensity of the PL fine peak from a single QD firstly increases, followed by a decrease, and is finally quenched. The observed force at which a PL peak disappears, i.e., the quenching force varies from QD to QD. This variation is ascribed to the diversely distributed strain fields in and around each QD and therefore can be related to the QD location with respect to the nanoprobe center. In order to clarify the mechanism of PL quenching, a numerical simulation of the strain distribution is carried out by a 3-dimensional finite element method. The modification of the energy band structure resulting from strain is then calculated based on the deformation potential theory. We concluded that the PL quenching observed experimentally can be attributed to the electron-repulsion resulting from the strain-induced potential gradient. Based on this mechanism, an indentation-induced shift of the electron-potential in bulk GaAs, at which the PL from QDs is quenched, was deduced to be 43.5-133.5 meV.
在一个扁平圆柱形纳米探针的弹性压痕作用下，测量了自组装InGaAs/GaAs量子点（QD）在低温（10 K）下的光致发光（PL）。该纳米探针会在自身周围产生局部应变场。随着压痕力增加，单个量子点的PL精细峰强度首先增加，随后降低，最终猝灭。观察到PL峰消失时的力，即猝灭力，因量子点而异。这种变化归因于每个量子点内部及其周围应变场的不同分布，因此可能与量子点相对于纳米探针中心的位置有关。为了阐明PL猝灭的机制，采用三维有限元方法对应变分布进行了数值模拟。然后根据形变势理论计算了应变引起的能带结构变化。我们得出结论，实验中观察到的PL猝灭可归因于应变诱导的势梯度导致的电子排斥。基于这一机制，推导得出块状GaAs中量子点PL猝灭时电子势的压痕诱导位移为43.5 - 133.5 meV。
