Optical spectroscopy and hyloscopy of monolayers of tungsten disulphide

Monolayers of transition metal dichalcogenides have been studied extensively during the last decade as they provide platforms for realization of valley-selective and spin-polarized optoelectronics. However, the existing fabrication techniques are far from meeting industrial needs and commonly result in randomly distributed monolayer islands with heterogeneous optoelectronic properties. Here, to study optoelectronic properties of these materials, optical imaging and time-resolved Raman techniques were developed. Deeper insights into the optical heterogeneities and crystal growth pathways were obtained using multi-dimensional analysis of spatially-resolved excitonic spectra, and dendritic domains of elevated n-doping levels were recognized. This research helps to resolve some conjectures regarding the nature of commonly observed spatial heterogeneities and offers an advanced method for examination of monolayer matter (hyloscopy). The latter, in turn, promises to advance the research around 2D materials and facilitate understanding of their properties and relevant fabrication techniques.