Atomic-scale spectroscopy of 2D Transition metal dichalcogenide heterostructures

Bilayers of 2H-WSe2 and 2H-MoSe2 form a type-II semiconductor heterostructure. A number of interesting optoelectronic phenomena have been observed in such heterostructures including charge transfer excitons, photovoltaic and photothermal effects, and Mott transitions at high exciton density. In this talk, we will describe complementary single-particle measurements of the electronic structure of these heterostructures using scanning tunneling microscopy (STM) and spectroscopy. Using a large-area exfoliation technique, coupled with pre-patterned electrodes to make ohmic contact to these bilayers, we have succeeded in fabricating devices that are compatible with surface-sensitive probes such as STM and angle resolved photoemission. We will describe the spatial structure of the bilayers including the effect of lattice mismatch on the electronic properties, as well as spectroscopic measurements performed under optical illumination both below and above the Mott threshold.