Electrochemical Detection of Isolated Nanoscale Defects in 2D Transition Metal Dichalcogenides
Marc Brunet Cabré, Aislan Esmeraldo Paiva, Matěj Velický, Paula E. Colavita, Kim McKelvey
Abstract
We show that nanometer and sub-nanometer scale defects in two-dimensional transition metal dichalcogenides can be detected electrochemically using scanning electrochemical cell microscopy (SECCM). We detect isolated anomalous electrochemical responses for the hexaammineruthenium ([Ru(NH3)6]3+/2+) redox couple on mono-, bi-, and trilayer regions of mechanically exfoliated MoS2. These anomalous sample points display faster electrochemical kinetics, with a diffusion-limited current plateau, compared to the surrounding sample points. The analysis of the electrochemical current suggests that the defects are equivalent to disk-shaped defects with radii of tens of nanometers, or to one-dimensional defects with nanometer to sub-nanometer widths. These results demonstrate that we can effectively isolate and electrochemically amplify the response from individual defects on a sample surface using SECCM, revealing features below the optical diffraction limit that would normally require high-resolution electron microscopy or scanning tunneling microscopy to detect.