“…Specifically, the quantum size effects could cause semiconductors with splitting of the electron energy band where the transitions within the band could approach to the microwave energy and lead to absorption of microwave energy. , The rich pool of semiconductors, including TiO 2 , ,,− g -C 3 N 4 , FeP, Mn x O y , , ZnO, SiO 2 , Fe x O y , and Cu 2– x S, ,− offers plenty of choices for possible materials candidates. Because of the highly self-doped feature, copper chalcogenide Cu 2– x S is attractive for its outstanding plasmonic properties in long-wavelength absorption and free electron movements in its various solid phases ranging from copper-rich Cu 2 S to copper-poor CuS, e.g., Cu 2 S, Cu 1.75 S, Cu 1.8 S, − Cu 1.96 S, and CuS. , …”