LAUSR

Optical properties of low-dimensional materials are strongly governed by excitons and their interactions with defects. For instance, non-radiative exciton decays in carbon nanotubes are presumably happened at defects and result in the low luminescence quantum yield [1]. On the other hand, specific defects in low-dimensional materials including carbon nanotubes, hexagonal boron nitrides and transition metal dichalcogenides modify their electronic structures and serve as dominant emission sites [2,3]. Thus the direct correlation between locally modulated exciton behaviors and atomic structures is necessary for further understandings. However the conventional light-probe emission/absorption spectroscopy has the inferior spatial resolution to assign an individual defect. For such local optical measurements, an electron probe in a transmission electron microscope (TEM), which can picture the atomic structures of materials and also induce optical excitations in single quantum objects, is quite useful. In addition, the recent development of a monochromator for TEM has pushed up the electron energy-loss spectroscopy (EELS) energy resolution to better than a few tens of millielectron volts, allowing us to identify the absorption peaks for optical excitation involving the quantum effects [4–8].