Abstract：

 

2D materials offer exciting new opportunities in electronics and opto-electronics due to their unique structure and associated properties. Graphene is the best known 2D material and is a zero-band gap semiconductor. However, there are a whole family of 2D materials that offer different properties to graphene, such as direct band gap semiconductors and insulators. These new 2D materials are set to expand the capability beyond what graphene alone can achieve and drive 2D materials into industry. In this talk I will discuss the recent work on monolayered transition metal dichalcogenides (TMDs) (MoS2 and WS2), which are direct band gap semiconductors that emit light in the visible spectrum. These are grown directly onto silicon wafers using scalable chemical vapour deposition methods with single crystal sizes up to 0.5mm. These TMDs have large exciton binding energy and enable the observation of trions and biexcitons using photoluminescence spectroscopy. Interactions with defect states will also be discussed. I will discuss our recent work on heterostructures of different 2D materials, formed by vertical stacking or lateral stacking, creating new systems with engineered excitonic dynamics for photodetectors, transistors, and light emitting devices fabricated at the nanoscale. Atomic resolution studies of defects in TMDs is studied using aberration corrected transmission electron microscopy, where single sulfur vacancies are detected and their dynamics of aggregation tracked in real time. I will show how we can probe substitutional dopants and adatoms that play major roles in n-type doping of transistors and enhanced catalytic properties. This talk will cover the aspects of TMDs from synthesis, characterization to implementation in nanoscale devices for wafer-scale electronics.