With the exfoliation of mono layer Graphene in 2004, plethora of 2D materials having metallic, semiconducting and insulating behavior has been discovered. The chemical stability of these materials and van der Waals bonding in out of plane direction means that these 2D materials can be stacked without constraints in different combination to produce new class of functional material. One important example of such devices is quantum tunneling transistors where an atomically thin insulator is sandwiched between two electrodes. When a voltage bias is applied between these electrodes, a tunneling current is observed. Such devices using 2D materials as insulator and electrodes have been demonstrated as transistors with current ON /OFF ratio of 106. Tunneling currents in such heterostructures strongly depends on the nature of the electrodes and the information about the density of states of electrodes can be obtained. Using such structure we propose to probe the density of states of various materials and fabricate the novel multi functional devices using them.