Study Of Charge Transport Through Five-Membered Heterocyclic Single-Molecule Junctions

With respect to a chemical substance,molecule is the smallest particle that is able to keep the primary chemical property.In recent years it is of great significance yet still challenging to study the electrical property of a single molecule.In brief,there are quite a number of issues that have impacts on charge transport through a molecule,such as the molecular structure,material of electrode,anchoring group,and quantum interference.For quantum interference in single-molecule electronics,so far most of the previous publications mainly focused on benzene rings and their hydrocarbon derivatives.On the other hand,in order to study the mechanism of charge transport through single-molecule junction,particularly the quantum interference,it is crucial to develop the instruments having ultra-high electronic characterization resolution and stability.During the past decades,mechanically controllable break junction(MCBJ)method has been widely adopted because of its advantages in stability and capability to tune gap size precisely in-situ.In this thesis,the single-molecule conductances of a series of five-membered heterocyclic compounds employing a home-built MCBJ instrument have been measured,and the influence of quantum interference on charge transport through them have been discussed.The contents and results are as follows:1.The single-molecule conductance of 1,8-octanedithiol(ODT)was measured by a home-built MCBJ instrument.To test the feasibility of our MCBJ instrument in studying single-molecule junction,the 1D conductance histogram,2D conductance-distance histogram and plateau length histogram were constructed.2.The single-molecule conductances of a series of five-membered heterocyclic compounds were measured by a home-built MCBJ instrument.Compared with the compounds with para-connections,the single-molecule conductances of the meta-ones were considerably lower.Moreover,it was found that for the meta-compounds,their single-molecule conductances were more sensitive to the heteroatoms that incorporated into the molecular structure.Then these observations were rationalized within the framework of quantum interference.