Figure 1.

Fabrication and characterizations of HfSe₂ oxide films and devices. a) Schematic illustration of Ti/HfSe _x O _y /HfSe₂/Au memristor. b) Optical image of the fabricated device. The crosspoint area is 5 × 5 µm². The inset images show AFM scan of the crosspoint (left lower panel) and AFM height profile (left upper panel) across the white line. c) XRD patterns of the HfSe₂ nanosheets on the SiO₂ substrate. d) Optical microscopy images of an exfoliated HfSe₂ flake with different thicknesses. The transparency of the flake increases after O₂‐plasma treatment, indicating the formation of Hf—O layer. e) Room‐temperature Raman spectra before and after 5 min O₂‐plasma treatment of HfSe₂ using a 532 nm laser. f) XPS spectra of Hf 4f core level for air‐exposed and O₂‐plasma‐treated HfSe₂ flakes.