Measurement of distribution of charge adsorbed on Au<i><sub>x</sub></i>/Si(111)-7×7 surface on an atomic scale in ultra-high vacuumстатья
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Аннотация:The physicochemical properties of Au atoms adsorbed on the surface on an atomic scale play a very
important role in preparing nanodevices and surface catalysis. In this paper, we use frequency modulated Kelvin
probe force microscopy (FM-KPFM)to study the multi-bit adsorbed charge distribution of Au on the surface of
Si(111)-(7×7) at room temperature. Firstly, the surface topography and local contact potential difference
(LCPD) of Au at different adsorption sites in Si(111)-(7×7) are successfully obtained by using home-made
ultra-high vacuum Kelvin probe force microscopy. Secondly, we analyze the atomic characteristics of specific
atomic positions of Au/Si(111)-(7×7) by force spectroscopy and potential difference, and realize the atomic
identification . The adsorption characteristics of Au/Si(111)-(7×7) surface charge transfer and Au are explained
by combining differential charge density calculations. The results show that Au atom adsorption mainly is in
the form of single atom and cluster . Specifically, the Au cluster is adsorbed at the three central positions of
Si(111)-(7×7) in a hexagonal structure of six atoms. Individual Au atoms are adsorbed to the positions of
central adatoms of Si(111)-(7×7). At the same time, through the measurement of potential difference, it is
known that a single Au atom and Au cluster lose electrons, presenting a positive electrical characteristic. The
results of surface differential charge density show that Au undergoes charge transfer during adsorption, losing
part of the charge, which locally reduces the work function at the position of the adsorbed atom. In the range of
distances where short-range forces, local contact potential energy differences and differential charge densities
change, the theoretical results and experimental results are in reasonable agreement.