Nanoelectronics based on truly two-dimensional materials has become a reality in the past few 
years. Due to its extraordinary electronic and mechanical properties, graphene has been investigated
 as prototype 2D material. However, the absence of a band gap and the difficulty to open a sizable 
one is defining the limits for the application of graphene as semiconductor substitutes. Alternative 
2D materials are required, and available in the much more general class of 2D materials beyond 
graphene.

Notably, many layered systems exhibit a large range of electronic properties, most of them being 
mechanically and chemically very stable. While the most studied 2D material, hexagonal boron 
nitride, is an excellent insulator, 2D semiconductors are found in particular for oxides and 
chalcogenides. High expectations for the emerging field of 2D electronics are in a materials class
that offers high mechanical and chemical stability complemented by a wide range of electronic 
properties - transition metal dichalcogenides (TMDs).

With the success of graphene, many production and characterization techniques have been 
developed that are applicable to the TMD field. Going beyond graphene, the key technology to 
produce 2D materials is based on exfoliation applied to layered TMDs and layer thickness can be 
determined by non-destructive optical microscopy. The enormous potential of 2D TMDs became 
evident when the first electronic devices on single-layer TMDs have been produced.