Tuesday 04 February 2020 16:00 – 17:00 A. Payatakes Seminar Room
“Electrochemical Raman spectroscopy of 2D materials”
Dr. Kyriakos Filintoglou Institute of Chemical Engineering Sciences (ICE-CT)
Abstract
Two- dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted attention recently due their unique physical properties (e.g. carrier mobility, appropriate bandgaps, rich excitonic effects, large spin-orbit coupling, spin-valley coupling). Besides, TMDCs raised a great interest for many applications such as optoelectronics, nanophotonics and valleytronics. Doping in 2D materials is an important strategy to precisely control their electronic and optical properties, without causing any induced structural disorder. In this study, we have successfully developed and tested a three-electrode electrochemical cell suitable for the electrical and in-situ Raman measurements. The single and few layer MoS2 and WS2 crystals have grown by a recently developed CVD method and have been investigated by a combination of Raman spectroscopy, Cyclic Voltammetry, and Impedance Spectroscopy. Impedance spectra suggest that the samples show pseudo-capacitive behavior. The Raman bands shift to higher frequencies with voltage application without any significant change in their widths and relative intensities. Finally, the MoS2 and WS2 were also studied by the application of biaxial mechanical strain. Our purpose is to construct a strain vs doping correlation plot based on the Raman measurements, providing an easy and fast way to determine the level of mechanical strain and carrier’s concentration of an unknown TMDC sample.