Fig. 2: Far field optical study.

Contour plot of (a) Raman (λL = 633nm), (b) PL (λL = 633nm) and (c) white light reflectivity spectra scans across a WSe2-MoSe2 heterojunction at T = 5 K. The black horizontal dashed line indicates the position of the heterojunction. Color bars for panels (a), (b) and (c) are normalized from 0 to 1. d Exciton diffusion measurements at a temperature of T = 4 K for the MoSe2 monolayer region (blue) and WSe2(red). In the inset we show the MoSe2 diffusion PL profile compared to the WSe2 one. The laser intensity profile (black) is shown to indicate over which area excitons are initially generated, with small intensity oscillations due to Airy discs visible in logarithmic scale. e Same as d but at T = 300 K.