Study on the negative differential resistance properties of self-assembled organic thin films by using STM

Currently, molecular devices are reported utilizing active self-assembled monolayers containing the nitro group as the active component, which has active redox centers [1]. We confirm the electrical properties of 4,4′-di(ethynylphenyl)-2′-nitro-1-benzenethiolate. To deposit the SAM layer onto gold electrode, we transfer the prefabricated Au(1 1 1) substrates into a 1-mM self-assembly molecules in THF solution. Au(1 1 1) substrates were prepared by ion beam sputtering method of gold onto the silicon wafer. As a result, we measured current-voltage curve using ultrahigh-vacuum scanning tunneling microscopy (UHV STM), I-V curve also clearly shows several current peaks in the negative bias region both −0.38 and 0.48 V.