Construction And Property Of Surface Nano-structure Based On Atomic Assembly

Nano structure refers to a new system based on nanometer material units,whose synthesis and assembly is to assemble nanoparticles,nanowires,nanotubes,etc.in a certain way to realize the required performance.It is of great significance in the whole nano-technology,and is the foundation of the whole nano-science and technology.This thesis foucues on the construction of nano-structures with unique functions via manipulations of atom or molecule and surface assisted chemical synthesis.The main findings in thesis are listed as following:1?The repeatable and reversible manipulaitons of silver atoms on Si?111?-?7x7?has been achieved at low temperature?106K?by realized by scanning tunneling microscope?STM?.A manipuaiton protocol is established so that a single silver atom on the reconstructed surface of Si?111?can be picked up and placed at the specified position on the surface by a STM tip.The high probability of such controllable manipulationallows us to construct variouls silver clusters with precise atomic number.A simple dynamic storage structure of information based on such controller manipulation on silver atom has been proposed.The“cluster-atom”nanostructures with different sizes were constructed on the surface of Si to realize the information write and read at nanometer scale.The number and location of the silver clusters can significantly adjust the diffusion behavior of a single silver atom located at the neighbored half unit cell due to the presence of long-range Colummb interaction.2?Under the condition of ultra-high vacuum,the repeatable manipulation of fullerene molecule(C₆₀)has been realized under low temperature?77K?by scanning tunneling microscope.The effects of the tunneling current and voltage,the tip distance and the control time on the success of the molecular manipulation have been studied systematically.Single fullerene molecules on Si?111?surface were adsorbed by STM tip and be released to the center of the faulted unit cell site on the reconstruction surface.Through the successful manipulation event for many times,the square root error between the center site of the half unit cell and the center of the target molecules is calculated to be less than 1?,which successfully showing the atom-level high precision molecular relocation manipulation on the surface of the Si?111?reconstruction.Using STM vertically manipulation,this kind of high-precision molecular relocation was also realized in the center of the unfaulted half unit cell and corner hole site,so that the molecules can be placed at any designated position on the reconstructed surface,laying a solid foundation for further assembling of artificial molecular devices.Ten C₆₀0 molecules were placed one by one in the corner hole of Si?111?surface through the vertical manipulation of the STM tip,a two-column molecular abacus was constructed artificially on the molecular scale,and the simple operation was conducted by“lifting”and“laying down”abacus beads(C₆₀ molecules)with STM tip.In principle,arbitrary addition and subtraction operations could be carried out within two digits.Meanwhile,by taking advantage of STM vertical manipulation,C₆₀ molecules on the surface of Si were“picked up”and released at the target location one micron away,and the micron level organic macromolecular transport was achieved for the first time,which provided the feasibility of assembling functional molecular nano-structures in the macro range in the future.3?Triangular graphene quantum dots have been prepared by pyrolysis of1,1'-ferrocene dicarboxylic acid on the surface of Cu?111?via surface chemical reactions.The presence of the non-magnetic local boundary state within the triangular graphene quantum dots are clearly revealed by measuring the spatial distribution of the local electron densities by STS.In addition,for smaller graphene quantum dot nanostructures?side length smaller than 7nm?.It is found that the non-magnetic energy splitting of the boundary state within this kind of quantum dots increases slightly with the decrease of the size of the graphene quantum dot,especially when the size of the quantum dot is smaller than 7 nm.The combination of the experimental observations and the DFT calculations reveal that the nonmagnetic boundary state is originated from the hybridization effect of graphene and substrate.