The Adsorption And Reaction Of H₄TCPP On Au(111) Surface At Atomic Scale

In the past decade,the rapid development of surface synthesis technology has made people realize that carbon-based micro-nano electronic devices are expected to break through the theoretical limit of silicon-based semiconductor.Yet practical application is limited to graphene that obtained from graphite.Thanks to the richness of organic molecules,we can control the precursor molecules and single control surface structure of the band gap,and other physical properties compared to traditional two-dimensional carbon material.The synthesis of precursor molecules as source material from bottom to top of two-dimensional single polymer materials,is expected to be the monolayer materials that can be applied to electromagnetism,optics,catalysis and other fields.However there are a lot of difficulties to be solved in the development of high molecular electronic devices based on organic molecules.The mainly lack of understanding of the surface reaction mechanism exists as well as the interaction between substrate and the structure is more complicated.These two problems are surface material transfer and regulation of the nature of the reaction products need to be considered,it is also the important reason for the limit its application in actual.In order to solve these problems.We used ultrahigh vacuum scanning tunneling microscopy(UHV-STM)combined with density functional theory(DFT)to calculate and study the charge transfer and reaction mechanism of 1,2,4,5-tetra(4-carboxyphenyl)benzene(H₄TCPP)molecule in the process of thermal excitation to find structural phase transition on Au(111)surface.First,we researched the self-assembled structure of H₄TCPP molecule on the surface of Au(111).Then,after annealing,it was found that the surface molecules migrated and formed a regular non-covalent single-layer network structure bound by H bonds.The carboxyl group contained in H₄TCPP molecule reduced the energy of the system through the combination of dihydrogen bonds,and this structure on the experimental surface was stable at 160 degrees.After further annealing,a two-dimensional monolecular structure with dense arrangement was obtained,while most of the molecules were desorbed.Through experiments and theoretical calculations,the surface deprotonation was confirmed,and the adsorption energy and charge transfer of the surface were studied.We confirmed that the mechanism of phase transition of H₄TCPP molecule on Au(111)surface.The charge transfer of molecule in the process of structural change on metal surface was further researched to study the reaction mechanism of the surface.In this research,the interaction between Au(111)surface and H₄TCPP molecule was learned by studying the adsorption and reaction of H₄TCPP molecule.On the surface of Au(111),the reaction mechanism was explored by studying the charge transfer between the surface structure and the substrate.Further understanding of the interaction between structure and molecular,which can change the work function of metal surfaces,will help advance the application of monolayer surface materials in the field of electronics.