Functionalization of ultrathin MoS_2 by defect engineering

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The overall goal of this project is to develop strategies to functionalize 2D materials by means of ion-induced electronic excitations. The energy deposition via electronic excitations gives rise to defects which clearly differ from those created by conventional (i.e. singly charged keV) ion beams with respect to type, size and effciency. The ion-induced defects will be further modified e.g. by the adsorption of precursor gases or molecules. Our objective is to identify and quantify the relevant defect creation mechanisms by systematic experiments on single layer MoS_2 - as a representative of the material class of transition metal dichalcogenides - in combination with theoretical modelling. This approach builds the basis for effcient defect engineering strategies, i.e. it will enable us to predict and choose the optimum parameters for the controlled fabrication of a certain defect structure in a given sample. In particular, we will focus our attention on the functionalization of single layer MoS_2 for three different applications, each of which is based on a specific defect type. Based on our preliminary work these are: nanosized pores with a small size distribution suitable for water desalination or DNA sequencing, desulfurized MoS_2 nanostructures suitable for the hydrogen evolution reaction (HER), and defect engineered MoS_2 field effect transistors which may be used as optoelectronic switches.