Spectroscopic Studies on Sulfides and Selenides of Mo and W for Photoabsorbers

In this work, we present our findings on spectroscopic studies conducted on two transition metal sulfides and selenides formed with Mo and W. In the first part of the work, we present the temperature-dependent (~80 K to 573 K) frequency shifts of the Raman-active \({E}_{\text{2g}}^{1}\) and A_1g modes of multilayer molybdenum disulfide (MoS₂) formed using solution exfoliation, where a red-shift in the peak locations was observed with increasing temperature. After these spectroscopic studies, the semiconducting dispersion of MoS₂ was then integrated with graphene ink, to create an integrated inkjet-printed heterostructure photodetector onto flexible substrates, that was responsive within the visible regime. In the second part of the work, Raman and photoluminescence spectroscopy was utilized to analyze the phononic and electronic parameters in suspended bulk WSe₂ sheets, fabricated utilizing photolithography and wet chemical etching. The response of the PL spectra for WSe₂ on supported and suspended regions showed the indirect I-peak and the excitonic A-peak to be red-shifted in the latter case, with an increase in the emission intensity as well.