A comprehensive study of WSe2 crystals using correlated raman, photoluminescence (PL), Second Harmonic Generation (SHG), and Atomic Force Microscopy (AFM) imaging

Tungsten diselenide (WSe₂) is a transition metal dichalcogenide (TMDC) that belongs to a class of nanomaterials with potential in optoelectronic device applications. Several characteristics that define the electronic, optical, and thermal properties of these two-dimensional (2D) crystals are thickness, crystal symmetry changes, and growth defects. The combination of various techniques for investigating the same WSe₂ flake sample shows that various processes involved in producing the photoluminescence (PL) signal are correlated with the localized strain. The WSe₂ flake samples are observable by confocal Raman imaging and topographic homogeneity can be determined by atomic force microscopy (AFM). The edge of the flake shows strong variations, which could be explained by the correlation of the various techniques. In addition, second harmonic generation (SHG) 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.