Abstract
Ultrathin two-dimensional layered transition metal dichalcogenides (TMDs) have instigated great research interests fundamentally and technologically due to their unique electrical, mechanical, optical and spin-electronic properties. Similar to traditional semiconductors, TMDs’ properties and possible applications critically depend on their defects and doping materials so that these material’s conductivity could be controlled.
In this research, we shall firstly investigate the native defects in as-grown TMDs such as MoSe2 and WSe2 in order to understand the formation mechanism, the dependence of defect density of these defects and try to control those defects to improve the sample quality. Secondly, we shall focus on the intentional doping in TMDs with the purpose of tuning the sample’s conductivity so that desirable device applications can be achieved. To change the electron/hole conductivity, we have two strategies, one is to use some transition metals as substitutional p-type or n-type dopants during the sample growth. The other strategy involves surface modifications using molecular ions or metal nanoparticles. The main techniques involved in this research are molecular beam epitaxy (MBE) for sample growth and substitutional doping, scanning tunneling microscopy/spectroscopy (STM/S) and transport/optical measurements for detecting/probing the defects and doping.
Anyone interested is welcome to attend.