Fig. 2: Structural details and electronic character.

a,b, TEM imaging of formed molybdenene sheet and elemental mapping. c, HRTEM image of top surface of molybdenene. d, Zoomed-in image of marked region in c. Criss-cross patterns of atoms are observed with four-fold symmetry (region 1 in d) and hexagonal arrangements of atoms with sixfold symmetry (region 2 in d). e, Raman spectra of as-synthesized Mo whiskers and surface attained after subsequent peeling of top layer. The bottom spectrum for the final peeling step clearly shows distinct Raman peaks at ~405 cm⁻¹, which is characteristic of metallic phase, and its second overtone at ~810 cm⁻¹. For visual clarity oxide Raman peaks are red shaded and metallic Raman peaks are green shaded. Distinct metallic Raman signatures and flat sheets observed in FESEM, TEM and AFM establish synthesis of free-standing molybdenene. f, Layer dependence of molybdenene Raman spectra. g, I–V characteristics of Mo sheet placed on SiO₂ substrate. h, Molybdenene structure with fourfold symmetry obtained using DFT calculations. i, The minimum-energy curve to determine equilibrium interlayer separation for molybdenene surface with fourfold symmetry. j, DFT band structure calculations of fourfold structure of molybdenene.