Abstract
In the post-silicon era, two-dimensional (2D) materials emerge as one of the most competitive materials for potential substitution of silicon in semiconductor technology. Among 2D materials, graphene, black phosphorus (BP) and molybdenum disulphide (MoS2) are most studied, due to their high mobility, desirable optical properties and novel physics. First, I will show the quantum transport in high quality BP field-effect transistors in a sandwiched heterostructure. The high mobility ~ 3000 cm2V-1s-1 allows for the observation of quantum oscillations in thin-film BP. Then I will show the efficient bandgap tuning properties in BP we discovered recently, based on which widely tunable mid-infrared photodetectors are demonstrated, with a cutoff frequency over 7.7 micrometer. In the second part, I will introduce the quantum capacitance studies in graphene and the observation of resonant states in foreign-atom-decorated graphene. Then using this unique capacitance technique, we extract a layer-dependent dielectric constant in MoS2, showing the direct evidence of strong Coulomb interactions in monolayer MoS2. We further identify a metal-insulating transition point in capacitance spectroscopy, which is explained based on a percolation transition model. At last, I will show the applications of van der Waals heterostructures, built from 2D materials, such as ultrahigh mobility graphene transistors, tunable tunneling light emitting diode at room temperature and its single photon emission below 10 Kelvin.
Anyone interested is welcome to attend.