First-principles Study Of Electronic Transport Properties In C₆₀ Molecular Devices

In recent years, there have been increasing interest and development efforts in minia-turizing electronic devices. A number of single molecular electronic devices such as molecular wires, molecular switches, molecular diode, molecular field effect transistor (FET), molecular sensor etc. have been designed. Simultaneously, some novel behaviors including switching, coulomb blockade, Kondo resonance, rectification, negative differ-ential resistance (NDR), and memory elements have been reported. Molecular devices will play an important role in switches, rectifiers, photovoltaic, memories, logic circuit in the future. In this thesis, we have systematically investigated the electron transport prop-erties of C60 molecular devices based on first-principles combined with nonequilibrium Green's function (NEGF) and density-function theory (DFT).The transport behaviors of C60 molecular device constructed by a C60 molecule sandwiched between two (5,5) carbon nanotubes (CNTs) electrodes have been studied, and we have considered the effects of gas adsorption on the electronic transport properties. The results show that the current-bias curves are affected obviously by adsorbed H2O and CO molecule, but hardly effected by NO2 molecule. We also find an obvious NDR behavior at the certain bias while C60 molecular device adsorbed by H2O molecule. A mechanism is proposed for NDR behavior.We investigate the electronic transport properties of a molecular switch device based on double C60 molecules sandwiched between two (5,5) CNTs electrodes. The results show that the electronic transport properties can be tuned by change the relative distance between the two C60 molecules. In this molecular device, we can actualize two sorts of molecular device tuned by mechanism and voltage. These results are promising for application in molecular switch devices.