Interlayer Excitons Investigated by Nano-PL and Nano-Photocurrent Modalities

The stacking of two materials to control and tailor their opto-electronic properties has opened a new paradigm in materials research. For the monolayer Mo- and W- based transition metal dichalcogenides, stacking allows for control of many fundamental optical properties, such as the bandgap and nonlinear susceptibility. Charge transfer between the TMD layers leads to the formation of interlayer excitons that have received a great amount of scientific interest owing to their unique properties such as their permanent dipole moment and their interaction with the moire lattice. Many studies have investigated the optical properties of these fascinating excitations, but most have relied on diffraction limited laser spots which are many times larger than the largest moire periods. Local real-space optical studies of interlayer excitons remain a challenge. Here I will report on our recent efforts to study interlayer excitons in MoSe₂/WSe₂ heterostructures at the nanoscale. Combining tip-enhanced optical studies with nano-photocurrent measurements we see optical electronic effects on order the moire lattice period, as well as red-shifting of the ILE emission energy due to formation of nanobubbles. Our results show the promise and feasibility for optical studies of moire phenomena on their native length scales.