| 초록 |
Since new type of layered materials composed of alternating opposite charged layers, bismuth oxychalcogenides(BOCs) such as Bi2O2Se, have drawn considerable attention due to its physical properties suitable for high speed/low power consumption optoelectronic device, instant and quick determination of its crystallographic characteristics is crucial for large scalability and integration. Here, we suggest how crystallographic structure and quality can be projected through Raman spectroscopy analysis, which showed certain frequency modes at ~ 55, 89, 360, and 434 cm-1 predicted only by theoretical calculations. The structural defects, such as oxygen-rich edges in Bi2O2Se crystals and grain boundary, which accompanied by the sensitivity to the excitation energy, actuate low frequency modes positioned at 55 and 89 cm-1. Furthermore, ~55 cm-1 at the line defects exhibit strong two-fold polarization dependence analogous to the edges of graphene/graphite. Our results can provide insight to disentangle the mechanism to activate Raman active mode from IR active mode by defects and even to help to understand the electronic structures of new type of layered materials. As an important application, we suggest that line defects of nanoscale width in Bi2O2Se can be visualized by Raman spectroscopy. |
