Figure 1.

(a) Raman Stokes spectrum with a Stokes peak at 1369 cm-1 corresponding to an hBN monolayer. (b) an optical reflection image of a uniform CVD-grown hBN monolayer transferred onto a 300 nm thick SiO₂/Si substrate, the scale bar is 20 µm. (c) an AFM image of the hBN monolayer with cross-sectional height profile analysis showing the step height of hBN on SiO₂ to be 0.45 nm. (d) TEM image of a suspended hBN monolayer edge over Cu foil, the scale bar is 5 nm and the inset shows the selected area electron diffraction pattern with the expected hexagonal lattice structure of hBN monolayer (e) Schematic of the custom built PTFE electrochemical cell. Bare Cu or hBN-Cu samples were clasped in the PTFE cell with a 0.07 cm² area opening to the electrolytic solution.