Figure 2.

AFM and TERS characterization of Janus ${\mathrm{Mo}}_{\mathrm{Se}}^{\mathrm{S}}$ converted from MoSe₂. a) Optical microscopy image of CVD‐grown MoSe₂ on SiO₂/Si which is used as the precursor for the ALS conversion. b) Low‐magnification and c) atomic‐resolution STEM‐HAADF images of monolayer and bilayer regions of CVD‐grown MoSe₂. d) Contact potential difference (CPD) image of the transferred Janus ${\mathrm{Mo}}_{\mathrm{Se}}^{\mathrm{S}}$ flake on the gold substrate. e) The TERS map overlaid over the CPD image of Janus ${\mathrm{Mo}}_{\mathrm{Se}}^{\mathrm{S}}$. f) The TERS map showing the intensity distribution of correspondingly highlighted Raman modes in panel (g), namely–MoSe₂ A₁’ (red), ${\mathrm{Mo}}_{\mathrm{Se}}^{\mathrm{S}}$ A₁ ² (green), and ${\mathrm{Mo}}_{\mathrm{Se}}^{\mathrm{S}}$ A₁ ¹ (blue). g) The TERS spectra averaged over the correspondingly colored boxes in panel (f), which represent Janus monolayer ${\mathrm{Mo}}_{\mathrm{Se}}^{\mathrm{S}}$ (blue), ${\mathrm{Mo}}_{\mathrm{Se}}^{\mathrm{S}}$‐MoSe₂ vertical heterostructures (red), and crack (green) regions.