Mining Data to Reveal Hidden Physics in Two-Dimensional Semiconductors at Ultra-Small Length Scales
Talk by Dr. Nicholas J. Borys (Physics Dept, MSU)
2/28/2019 Wilson Hall 1-144 3:10-4:00pm
Transition metal dichalcogenide semiconductors, such as monolayer MoS2, are an emergent class of ultrathin thin semiconductors that are only three atomic layers thick yet host a rich suite of photophysical phenomena that provide new opportunities ranging from fundamental investigations of many-body physics to the development of new quantum devices. In these atomically thin semiconductors, the absorption of light creates an “exciton,” which is an excited electronic state composed of a negatively charged conduction band electron that is tightly bound to a positively charged valence band hole. These excitons govern light-matter interactions such as absorption and emission in 2D semiconductors and are fundamental packets of energy that can be manipulated, transported and harvested for next-generation technologies. Our work concentrates on studying nanoscale excitonic phenomena in 2D materials by using nano-optical imaging and spectroscopy techniques to probe light-matter interactions at length scales that are significantly smaller than what is accessible with conventional optical microscopy. Achieving spatial resolutions as high as 15 nm, approximately 20x better than conventional optical microscopy, we have uncovered a striking diversity of regions of excitonic phenomena that are associated with “nanobubbles" of strain, charge puddles, disordered edges and grain boundaries in 2D atomically thin semiconductors. Within these diverse optoelectronic regions, using techniques inspired by those of the fields of big data and data mining, we have been able to resolve exciton quenching and localization effects, and from these studies are now taking initial steps to leverage such nanoscale phenomena to pattern excitonic circuitry in 2D semiconductors for model optoelectronic and quantum excitonic devices.