Modifications of 2D-Transition Metal Dichalcogenides by Metal Incorporation

Van der Waals materials are stable as free-standing 2D sheets in various environments and can readily be manipulated and integrated with other materials. Here we explore if such 2D transition metal dichalcogenides can be modified by reaction with excess metals to create novel 2D materials and nanostructures. We show that for some transition metal dichalcogenides (TMDs) the notion of a weak interaction with vapor deposited metals is not always true and their 2D-crystal structure can be react with metals. We discuss this on the example of two different TMDs, semiconducting Mo-dichalcogenides and semi-metallic PtTe₂. For the former we show that Mo-deposition results in the formation of metallic 1D line-defect networks and we discuss the underlying materials physics of their formation. Moreover, the 1D electronic nature of these defects, embedded in the semiconducting host material, is confirmed by angle resolved photoemission spectroscopy that shows signatures of a Tomonaga Luttinger liquid. The modification of MoSe₂ can also be expanded to hetero-atoms and these may induce magnetism in the material, forming a diluted ferromagnetic 2D-semiconductor. Finally, for PtTe₂ we show that vacuum annealing results in a loss of Te and the formation of several compositional Pt-Te van der Waals materials. Moreover, we show that these compositional variants can also be obtained by reacting 2D-PtTe₂ (ditelluride) with deposited Pt-atoms to form metastable 2D-PtTe (monotelluride). These results show that 2D van der Waals materials surfaces can exhibit a surprising flexibility in incorporating excess metal atoms and form new, metastable materials with largely unexplored properties.