Facile Resist‐Free Nanopatterning of Monolayers of MoS2 by Focused Ion‐Beam Milling

Abstract

AbstractNanopatterning of monolayers of transition metal dichalcogenides offers a new avenue for the creation of nanoscale light sources and their integration into hybrid nanophotonic systems. Here, focused gallium ion‐beam milling is employed as a resist‐free and simple nanofabrication approach to pattern MoS2 monolayers grown by chemical vapor deposition into nanoribbons. Using photoluminescence (PL), Raman, and valley polarization spectroscopy, it is investigated how the optoelectronic properties of the MoS2 monolayers are affected by the nanopatterning as a function of the ion fluence used for milling. Characteristic spectral shifts in the Raman and PL peaks are observed, which are indicative of a release of strain in patterned MoS2 monolayers as compared to the as‐grown monolayers. Furthermore, while the total PL signal is reduced in the patterned monolayers, using circular‐polarization‐resolved cryogenic PL spectroscopy it is shown that the valley polarization is well preserved for monolayers patterned within an optimal ion‐fluence range. The results and in particular the observed robustness of the valley polarization indicate that focused ion‐beam nanopatterned MoS2 monolayers are interesting candidates for their integration into hybrid quantum systems consisting of designed photonic nanostructures and precisely placed nanoscale excitonic light sources.