Nano-Optical Studies of Individual Nanostructures

Optical techniques play a significant role in studies of nano-structures. The electronic structures of quantum dots, for example, vary with the geometric sizes in an ensemble, resulting in broadened spectral lines. Recently, different forms of local spectroscopic techniques have been applied to investigate such inhomogeneously broadened emission lines. In this paper we report on three methods for local spectroscopy: cathodo-luminescence, luminescence induced by a scanning tunnel microscope and microphotoluminescence. Each of these techniques is shown to have the capacity to investigate single quantum dots, with linewidths in the range 40–1000 µeV. Besides demonstrating the possibility of imaging and spectroscopically studing individual dots, we also demonstrate the possibility of investigating single impurity atoms, in imaging as well as in emission spectroscopy modes.