NCAFM2023 Programme Booklet

LOCAL CONTACT POTENTIAL DIFFERENCE MEASUREMENT OF ADSORPTION ON THE SURFACE OF Au x /Si(111)-7×7 BY AFM/KPFM

P. L. Shu 1,2 , J. Feng 1,2 , Q. Guo 1,2 , X. S. Ren 1,2 , H. F. Wen 1,2 , J. Tang 1,2 , Z. M. Ma 1,2* , J. Liu 1,2 .

1 State Key Laboratory of Dynamic Measurement Technology, North University of China, 030051 Taiyuan, China. Email: mzmncit@163.com. 2 School of Instrument and Electronics, North University of China, Taiyuan 030051, China.

The physicochemical properties of Au atoms adsorbed on the surface of the atomic scale play a very important role in the preparation of nanodevices and surface catalysis. In ours studies, we used electron beam evaporation to evaporate Au atoms on the surface of clean Si(111) sample at room temperature, and selected 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) were successfully obtained by using self-made ultra-high vacuum Kelvin probe force microscopy. Secondly, we analyzed the atomic characteristics of specific atomic positions of Au/Si (111) -(7×7) by force spectroscopy and potential difference, and atomic identification was realized. The adsorption characteristics of Au/Si (111)-(7×7) surface charge transfer and Au were explained by combining differential charge density calculations. The results showed that Au atom adsorption mainly had single atom and cluster forms. Among them, the Au cluster is adsorbed in a hexagonal structure of six atoms in the three of Si (111)-(7×7). Individual Au atoms are adsorbed to the 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 and have a positive electrical characteristic. The results of surface differential charge density show that Au undergoes charge transfer during adsorption and loses 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, reasonable agreement between theory and experiment is obtained.

Fig. A single Au atom (left) and Au cluster (right) absorbed on Si(111)-7×7 surface.(a) Topography; (b) VLCPD images; (c) line profiles of topography; (d) line profiles of VLCPD. References [1] H. Y. Wang, J. Feng, X. D. Wang, Y. Wen, J. Y. Wei, H. F. Wen, Y. B. Shi, Z. M. Ma, Y. J. Li, J. Liu. Acta Phys. Sin., 2022, 71, 060702. [2] J. Feng, Q. Guo, P. L. Shu, Y. Wen, H. F. Wen, Z. M. Ma, Y. J. Li, J. Liu, I. V. Yaminsky. Acta Phys. Sin., 2023, 72, 110701. [3] Z. Qu, Y. Sugawara, Y. J. Li. J.Phys.: Condens, Matter., 2023, 35, 185001. [4] Y. Adachi, H. F. Wen, Q. Z. Zhang, M. Miyazaki, Y. Sugawara, Y. J. Li. Nanoscale Adv., 2020, 2, 2371.

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