Fig. 9
From: Room temperature multi-phonon upconversion photoluminescence in monolayer semiconductor WS2
Optical microscope contrast and AFM image of WS2/hBN/SiO2/Si structure. a The optical microscope contrast image of WS2/hBN/SiO2/Si structure. The dashed black triangle shows the area corresponding to WS2 flake, whereas the red and green rectangles point out the areas corresponding to WS2/hBN/SiO2/Si and hBN/SiO2/Si, respectively. b The AFM image of the area indicated by the red rectangle in a. c The AFM image of the area indicated by the green rectangle in a. d The height profile along the red line overlaid on the image in b. e The height profile along the green line overlaid on the image in c
