Fabrication And Electrical Properties Of Carbon Nanotube And Graphene Hybrid Structure

As a new nano material, Carbon nanotubes(CNTs) have excellent electrical, thermal, and mechanical properties, and will be widely used in future nanoelectronics field. However, the contacts between CNTs and other materials in the application are affected by schottky barrier. Graphene has a similar structure with CNT, zero band gap, high electron mobility at room temperature, and small schottky barrier between graphene and CNTs contact, this make it as an ideal electrode of CNT devices. In this thesis, we simulated the electron transport of graphene and CNTs contacts, fabricated the hybrid structures and measured their electrical properties, which provides a foundation for widely used carbon electronic devices.In the simulation of electron transport properties in the graphene and CNTs contact by ATK software, different structure models were considered, we studied the transmission coefficient with respect to graphene defects. The electronic transport path, current density, electron density, the I-V characteristic curve features were investigated, which gives a theoretical reference to experimentally study graphene and CNT contact. The simulation shows that vacuum gap hinders the electron transport in the contact, resulting in an additional contact barrier. The electron transmission is mainly performed between the boundary carbon atoms of the CNT and the nearest graphene atoms, and the imperfection of the edge carbon atoms in a hexagonal lattice destroys the ballistic transport in graphene and the CNT at the contact.In the preparation of the hybrid structure, the metal electrode for measurement were obtained by semiconductor fabrication process mainly including photolithography, magnetron sputtering, stripping, and graphene electrode to link CNT was transferred and patterned by RIE etching. The CNTs were located between graphene electrodes using DEP technology. The annealing effect on the graphene electrode and the DC resistance characteristics of the structures were studied. We also studied the temperature coefficency of resistance. Results showed that the hybrid samples had positive temperature coefficient, although it is negative in pure CNTs. The increasing temperature causes graphene deformation which might lead to defects because of the different thermal expansion coefficient of graphene and substrate. The increasing graphene resistance may thus offset the decreasing carbon nanotubes resistance. The AC electrical properties of the hybrid structure were also tested afterwards. They demonstrated capacitive behaviors at 20 kHz and higher. We speculate that the adsorption of oxygen and imputrity defects during the fabrication process make the quantum capacitance and effective inductance increase, and the additional capacitance weights more than the inductance of the contact part when the input signal goes to high frequency...