Regulating Electron Transport In Molecular Devices By Plasmons

Plasmon and molecular electronics are two different fields to explore the physical phenomena of the nanometer scale.The plasmon polaritons are induced by the interaction of nanoparticles with light and form local strong electromagnetic field on the metal surface.Molecular electronics measures the properties of molecules by electrical means to realize the application of molecular devices.Using plasmon to control molecular devices can break through the diffraction limit of traditional optics to focus and achieve efficient control of electron transport behavior in molecular junctions.Meanwhile,it can improve the compatibility of single molecular devices and integrated optical devices.This dissertation has carried out the following work for this topic.1.Designed and constructed a Mechanically Controllable Break Junction?MCBJ?instrument with attenuation factors of 10^-10.It can be variable change electrode spacing for precisely measure the electron transport in the molecule.The device mainly applies the principle that the larger the cross-sectional area of liquid is,the shorter the height of the cavity is.Through a small force,the piston in the cylinder with a small cross-sectional area can be moved long distances,and the cylinder with the larger cross-sectional area can be moved short distances.The thrust is finally applied to the MCBJ chip to break the molecular junction through a push rod connected to a large hydraulic cylinder piston.2.Build a home-made graphene/copper hybrid electrode in order to better explore the modulation of light on molecular charge transport.It was made by growing the double-layer graphene on the copper wire,which cut a notch in the middle by chemical vapor deposition?CVD?method.It is more stable and compatible than metal electrodes and can produce stronger localized surface plasmons?LSP?.By measuring the conductance of graphene,it is found that LSPRs produced in the gap of the cracked electrodes can broaden the conductance of graphene under 632.8nm laser irradiation.3.Using molecules with optical switching effects?can convert structures by exposure to UV/visible light?and study the effect of plasmon on molecular conductivity.The conductance of the two kinds of isomers in the dark and illuminated environment was compared through the histogram.The results show that the molecule can exhibit three conductivity values of ring-open,ring-closed dark,and ring-closed UV light by light control.Finally,we fabricate an MCBJ chip with the metal-insulator-metal?MIM?structure to investigate the response of surface plasmon polaritons?SPPs?to molecular charge transfer.Based on SWMJs technology,we electrophoresis nanowires with self-assembled optical switch molecules onto the gold electrode to realize unidirectional molecular optical switch.