Controlled Charge Transport in Single-Molecule Electronics

As the semiconductor companies officially abandoned the pursuit of Moore's law, the limitation of silicone-based semiconductor electronic devices is approaching. Single molecular devices are considered as a potential solution to overcome the physical barriers caused by quantum interferences. In this bottom-up approach, components are built from atoms up, allowing great control over the molecular properties. This thesis describes the design, synthesis, and measurement of a series of molecular wires utilizing the pyridinoparacyclophane (PC) structure as a gate. A model system of molecular transistor was synthesized and demonstrated by STM break-junction technique. The gating effect in the molecular wire was originated from the tuning of the energy levels via dipolar field and can be turned on/off by dipolar field and chemical stimulation. This is the first example of gated charge transport in molecular electronics. The same concept was also applied to a molecular wire system to create a molecular diode with tunable rectification ratios. Finally, a series of ladder-type fused heteroacenes molecular wires was synthesized and investigated. It was found that this molecular wire system possesses exceptional charge transport properties with weak length dependence, allowing the molecular wires to better mediate charges over long distance.