Fig. 2: Bandgap Eg ≈ 200 meV in DCA3Cu2 MOF on hBN/Cu(111).
From: Local gate control of Mott metal-insulator transition in a 2D metal-organic framework
a dI/dV spectra at MOF positions indicated by orange markers in b–e and on bare hBN/Cu(111) (grey dots) (setpoint: Vb = −500 mV, It = 500 pA). Grey dotted vertical lines indicate bias voltages at which STM images were acquired in b–e. Spectra offset for clarity. Dashed horizontal lines indicate dI/dV = 0 reference for each curve. Spectra reveal a bandgap Eg ≈ 200 meV. The non-zero dI/dV within the gap is due to states of underlying Cu(111) leaking through hBN. Red squares (circles): lower Hubbard band maxima, LHBM (upper Hubbard band minima, UHBM). b–e STM images of MOF on hBN/Cu(111) at specified bias voltages (It = 10 pA). White dashed circle: hBN/Cu(111) moiré pore. MOF unit cell indicated in light blue. Scale bars: 1 nm. Insets: zoom-in of region within red box, with overlaid Cu-DCA-Cu chemical structure, showing significant contributions from the ends of the DCA anthracene moiety (green arrow) and Cu (orange arrow) for Vb < LHBM and Vb > UHBM. Right inset in d: charge density isosurface (0.0025 e− Å−3) of DCA3Cu2 obtained by integration of near-Fermi (±0.5 eV) DFT wavefunctions.
