State Key Laboratory of Surface Physics, Fudan University, Shanghai, People's Republic of China.
Nanotechnology. 2011 Mar 25;22(12):125601. doi: 10.1088/0957-4484/22/12/125601. Epub 2011 Feb 14.
The size uniformity of self-assembled SiGe quantum rings, which are formed by capping SiGe quantum dots with a thin Si layer, is found to be greatly influenced by the growth temperature and the areal density of SiGe quantum dots. Higher growth temperature benefits the size uniformity of quantum dots, but results in low Ge concentration as well as asymmetric Ge distribution in the dots, which induces the subsequently formed quantum rings to be asymmetric in shape or even broken somewhere in the ridge of rings. Low growth temperature degrades the size uniformity of quantum dots, and thus that of quantum rings. A high areal density results in the expansion and coalescence of neighboring quantum dots to form a chain, rather than quantum rings. Uniform quantum rings with a size dispersion of 4.6% and an areal density of 7.8×10(8) cm(-2) are obtained at the optimized growth temperature of 640°C.
自组装的 SiGe 量子环的尺寸均匀性，是通过用一层薄的 Si 覆盖 SiGe 量子点形成的，其大小均匀性受到生长温度和 SiGe 量子点的面密度的极大影响。较高的生长温度有利于提高量子点的尺寸均匀性，但会导致 Ge 浓度降低以及量子点中 Ge 分布不对称，这会导致随后形成的量子环在形状上不对称，甚至在环脊的某个地方断裂。较低的生长温度会降低量子点的尺寸均匀性，从而降低量子环的尺寸均匀性。高面密度会导致相邻量子点的扩展和合并形成链，而不是量子环。在优化的 640°C 生长温度下，获得了尺寸分散度为 4.6%、面密度为 7.8×10(8)cm(-2)的均匀量子环。
