Fig. 4: Transition from a molecule’s transiently charged state to the neutral charge state by tunneling through the NaCl barrier.
From: Charge-state lifetimes of single molecules on few monolayers of NaCl
The frontier molecular levels, chemical potentials of tip (μt) and sample (μs), and the interface state (IS) are indicated. The shown level alignment corresponds to voltages of the ion resonances deduced from the positions of the neutral molecule’s ion resonances and STML. The dashed lines indicate which single electron states derive from the HOMO (lower pair of states) and LUMO (higher pair of states) of the neutral molecule, the corresponding α and β spin channels are indicated. The gray shaded area indicates the linewidth of the levels. Because of different work functions, the vacuum-level aligned molecular ion resonances are shifted to larger bias values on Au(111) compared to Cu(111)12,32. Thicker (thinner) arrows indicate channels that involve (do not involve) the IS. In a–c, the IS contributes to at least one channel, while in d, it does not. A more detailed depiction of how the shown level alignment was derived is shown in the Supplementary Fig. 5. By schematically showing the conduction band minimum (CBM) and valence band maximum (VBM) of NaCl we indicate the need to consider the band structure of NaCl for tunneling. Refs. 67,68,69. suggest that the CBM is roughly aligned with the vacuum level while the band gap is at least 8 eV (see Supplementary Note 5).
