▎ 摘　　要

We find negative differential resistance (NDR) at room temperature in ultrathin films of nickel (II) 1,4,8,11,15,18,22,25-octabutoxy-29H, 31H-phthalocyanine [NiPc(OBu)(8)] deposited on highly ordered pyrolytic graphite (HOPG) substrate [NiPc(OBu)(8)/HOPG] and NiPc(OBu)(8) on graphene oxide (GO) deposited on HOPG [NiPc(OBu)(8)/GO/HOPG]. For the NiPc(OBu)(8)/HOPG system, NiPc(OBu)(8) was transferred four times onto HOPG by the Langmuir-Blodgett (LB) technique. We have prepared a stable Langmuir monolayer of amphiphilic GO at the air-water interface and transferred it onto HOPG by the LB technique. Further, the monolayer of NiPc(OBu)(8) was transferred four times for good coverage on GO to obtain the NiPc(OBu)(8)/GO/HOPG system. The current-voltage characteristics were carried out using a current sensing atomic force microscope (CSAFM) with a platinum (Pt) tip that forms Pt/NiPc(OBu)(8)/HOPG and Pt/NiPc(OBu)(8)/GO/HOPG junctions. The CSAFM, UV-visible spectroscopy, and cyclic voltammetry studies show that the NDR effect occurs due to molecular resonant tunneling. In the Pt/NiPc(OBu)(8)/GO/HOPG junction, we find that due to the presence of GO, the features of NDR become more prominent. Also, GO causes a shift in NDR voltage towards a lower value in the negative bias direction. We attribute this behavior to the role of GO in injecting holes into the NiPc(OBu)(8) film. Published by AIP Publishing.