Fig. 3.

SPEM images and μ-PES measurements on the WSe₂ pn homojunction. Se 3d, W 4f, and Bi 4f core-level photoelectron spectra measured with SPEM in P_up and P_down regions of a WSe₂/BFO homojunction. a Core-level spectra of Se 3d and W 4f recorded from a P_down (blue) and a P_up (orange) region. SPEM images of W 4f taken in 34.6 eV and 35.4 eV, which correspond to a P_down and a P_up region, respectively. b Core-level spectra of Bi 4f emitted from the BFO substrate. c The band structure deduced from a reveals the pn junction for WSe₂ in P_down and P_up regions near 300 K