Interface-engineered electrical transport properties in benzenedithol self-assembled monolayer molecular junctions using chemically p-doped graphene electrodes*

In this study, we fabricated molecular junctions consisting of self-assembled monolayers of benzenedithiol (BDT) using p-doped multi-layer graphene electrode. The p-type doping of graphene film was done by treating pristine graphene (work function of ~4.40 eV) with trifluoromethanesulfonic (TFMS) acid, resulting in an increased work function (~5.23 eV). The chemically p-doped graphene-electrode molecular junctions statistically showed an order of magnitude higher current density with a lower charge injection barrier height than those of pristine graphene-electrode molecular junctions, as a result of interface engineering. This enhancement is due to the increased work function of TFMS-treated p-doped graphene electrode in highest occupied molecular orbital (HOMO)-mediated tunneling molecular junctions. The validity of these results was proven by theoretical analysis based on coherent transport model considering asymmetric couplings at electrode-molecule interfaces.

References
[1] Han et al., Angew. Chem. 55, 6197 (2016).