*일시: 11월 9일(목) 오후 4시 30분
*장소: 베어드홀 103호
*연사: 이기주 교수(충남대 물리학과)
*제목: Optical Characterization of 2D Layered Semiconductors
Due to unique optoelectronic properties two-dimensional layered semiconductors such as MoS2, WSe2, and black phosphorus(PB) are attracting much interests.
Energy gap varies with the layer number and the direct to indirect gap transition makes much stronger light emission in monolayers than in thicker layers. By stacking different monolayers, layered heterostructures can be obtained easily. These materials are also known for strong excitonic signatures and valley-dependent optical interactions.
I present on the optical characterization of WSe2, MoSe2, and BP. By applying the transfer matrix method on the reflectance and transmittance spectrum, we obtain dielectric constants of monolayer WSe2 and thick layer BP. Monolayer WSe2 exhibits strong excitonic transitions with large spin-orbit splitting, and a large anisotropy is observed in BP. I also discuss on ultrafast processes involving the dynamics of spin, exciton, and phonons, from experimental results of the pump-probe technique with femtosecond pulses.