Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK.
Nat Nanotechnol. 2012 Oct;7(10):646-50. doi: 10.1038/nnano.2012.142. Epub 2012 Aug 26.
Strained semiconductor nanostructures can be used to make single-photon sources, detectors and photovoltaic devices, and could potentially be used to create quantum logic devices. The development of such applications requires techniques capable of nanoscale structural analysis, but the microscopy methods typically used to analyse these materials are destructive. NMR techniques can provide non-invasive structural analysis, but have been restricted to strain-free semiconductor nanostructures because of the significant strain-induced quadrupole broadening of the NMR spectra. Here, we show that optically detected NMR spectroscopy can be used to analyse individual strained quantum dots. Our approach uses continuous-wave broadband radiofrequency excitation with a specially designed spectral pattern and can probe individual strained nanostructures containing only 1 × 10(5) quadrupole nuclear spins. With this technique, we are able to measure the strain distribution and chemical composition of quantum dots in the volume occupied by the single confined electron. The approach could also be used to address problems in quantum information processing such as the precise control of nuclear spins in the presence of strong quadrupole effects.
应变半导体纳米结构可用于制造单光子源、探测器和光伏器件，并有可能用于创建量子逻辑器件。这些应用的发展需要能够进行纳米级结构分析的技术，但通常用于分析这些材料的显微镜方法具有破坏性。NMR 技术可以提供非侵入式结构分析，但由于 NMR 光谱中显著的应变诱导四极矩展宽，因此仅限于无应变半导体纳米结构。在这里，我们展示了可以用光探测 NMR 光谱法来分析单个应变量子点。我们的方法使用具有特殊设计的光谱模式的连续波宽带射频激发，并可以探测仅包含 1×10(5)个四极核自旋的单个应变纳米结构。通过这项技术，我们能够测量单个受限电子占据的体积内量子点的应变分布和化学成分。该方法还可用于解决量子信息处理中的问题，例如在存在强四极矩效应的情况下对核自旋进行精确控制。
