Correlative imaging of transition metal dichalcogenides

Transition metal dichalcogenides (TMDCs), belong to a new class of nanomaterials with great potential for optoelectronic device applications. These single or few layer materials exhibit unique electronic and optical properties, which are significantly different from the bulk precursor. Bandgaps of semiconducting TMDCs can be tuned by changing the number of layers, the chemical compositions, or the strain of the materials Thickness, changes in crystal symmetry, and growth defects are a few parameters that define the electronic, optical, and thermal properties of 2D crystals and for which different characterization techniques are required. In this contribution the combination of various techniques for investigation of the same crystals shows that various processes involved in producing the photoluminescence signal are correlated with localized strain as observable by confocal Raman imaging and topographic homogeneity as determined by atomic force microscopy. The edge of the 2D crystals show especially strong variations, which can be explained by the correlation of the various techniques. Second harmonic generation measurements identify grain boundaries as potential sources of strain relief, which is in agreement with both the confocal Raman as well as the confocal PL results.