Fig. 2.

The scanning probe microscope images and μ-PL spectra of the WSe₂ pn homojunction. WSe₂ on P_up and P_down regions from measurements with an AFM and PL. a, b AFM and PFM taken of a WSe₂ sheet on the BFO ferroelectric layer as grown. The solid line shows poled regions with bias −8 V at an AFM tip (yellow lines). A PFM image taken of a WSe₂ sheet on a BFO layer with P_up and P_down regions, which shows the out-of-plane ferroelectric polarization in BFO to have phase difference 180°. c KPM image and line profile image taken across and outside the P_up and P_down homojunction. d PL of a WSe₂ sheet taken from the P_up and P_down homojunction. The scale bars in the figures are 5 μm