2H相におけるCrO2単層のエキシトン効果と光学的特性

The development and proposal of new 2D materials have been expanding the frontiers for new technologies in the field of photovoltaics and optoelectronics with ultra-thin materials, especially 2D semiconductor materials. As known in the literature, the CrO 2 in 2H phase presents semiconductor characteristics, but the excitonic effects and optical properties have not yet been systematically investigated. In this sense, a significant gap in the understanding of its potential for optoelectronic applications needs to be overcome. Here, we performed a systematic investigation of its structural, electronic, excitonic, and optical properties. We identified it as being dynamically stable, with a favorable synthesis temperature around 660 K. Also, it was determined to be an indirect band gap semiconductor (0.93 eV), with a direct band gap of 1.84 eV located in K/K' valleys. Excitonic effects play an important role in the description of the linear optical response, with an exciton binding energy of 386 meV. Furthermore, these quasi-particle effects give rise to an indirect excitonic ground state, resulting in an optical band gap of 1.20 eV, which is significantly smaller than the direct electronic band gap. Consequently, high reflectivity is observed in the UV region with potential applications as a UV filter.