Fig. 3. Electronic properties of three representative planar acetylene-linked oxa-nanographenes on Au(111).
a, c, e Chemical structures, STM images, and dI/dV spectra recorded on different locations (marked in the inset STM image) of three representative planar acetylene-linked oxa-nanographene dimers (a: α,α-dimer; c: β,β-dimer; e: α,β-dimer). The gray curves were taken on a bare Au(111) surface, demonstrating the Shockley surface state of Au(111) at around −0.4 V. b, d, f Constant-current dI/dV maps of three representative planar acetylene-linked oxa-nanographene dimers (b: α,α-dimer; d: β,β-dimer; f: α,β-dimer) conducted at indicated energies and the corresponding calculated LDOS of HUMO and mixed LUMO containing LUMO and LUMO + 1 (HSE06 results, see detailed settings in Methods). The Fermi level is set to zero. Scale bars of STM images: 0.5 nm. Scanning parameters of STM images: a U = 0.6 V, I = 200 pA. c U = 0.1 V, I = 50 pA. e U = 0.5 V, I = 50 pA.