Adsorption and Migration of Silver on Group IV Semiconductor (001) Surfaces

Adsorption and Migration of Silver on Group IV Semiconductor (001) Surfaces

Sep 13th

15:30

Xiaohang Huang (Profs. Kai Huang (GTIIT) and Alon Hoffman (TIIT))

Adsorption and Migration of Silver on Group IV Semiconductor (001) Surfaces

Xiaohang Huang

Chemistry Program, Guangdong Technion-Israel Institute of Technology, Shantou, China;

Schulich Faculty of Chemistry, Technion−Israel Institute of Technology, Haifa, Israel

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This research was conducted under the supervision of

Profs. Kai Huang (GTIIT) and Alon Hoffman (TIIT)

In Zoom

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Adsorption and Migration of Silver on Group IV Semiconductor (001) Surfaces

In our recent work,¹ scanning tunneling microscopy (STM) and density functional theory (DFT) were employed to examine the dynamics of adsorption and the subsequent growth of submonolayer silver on Si(001) from 100 K to 230 K. The most telling findings was the direct access of isolated silver in the form of Ag₂ and Ag₄. In the current work,² we extend our DFT studies to the adsorption and migration of silver (Ag₁, Ag₂ and Ag₄) on the (001) face of group IV(001) (IV = C, Si and Ge) semiconductor surfaces. For Ag₁ on IV(001), the adsorption is favored to be covalently attached at the trench between substrate rows, yielding the heats of adsorption of 1.91, 2.53 and 2.07 eV on C(001), Si(001) and Ge(001), respectively. The migration of Ag₁ is, however, by way of the substrate rows regardless of migration direction, giving isotropic barriers of 0.08, 0.51 and 0.38 eV on C(001), Si(001) and Ge(001), respectively. As the size of silver increases, there emerge quasi-covalent adsorbate-adsorbate (Ag-Ag) interactions, in addition to the covalent adsorbate-substrate interactions, as showcased by the adsorption of Ag₂ and Ag₄ on Si(001). The heats of adsorption are 2.16 for Ag₂ and 2.53 eV for Ag₄. Consequently, the migration of Ag₂ and Ag₄ is enabled inside the trench between Si-rows, leading to anisotropic barriers; the migration of Ag₂ favors across (0.26 eV in barrier) over along (0.63 eV in barrier) Si-rows, whereas the migration of Ag₄ favors along (0.24 eV in barrier) over across (0.68 eV in barrier) Si-rows. Since the group IV elements are of vital importance in the semiconductor industry, there is applied interest in fabricating novel nanostructures of metals on semiconductors by tuning the dynamics of adsorption and migration, as unveiled in the present work.

Our research was supported in part by the National Natural Science Foundation of China (NSFC, Grant No. 21902036), the Ministry of Science and Technology of China (MOST, Grant No. QNL20200230004), Guangdong Province “Special Project and Task List” Funding (Grant No. 2020ST065 and STKJ2021195), and 2020 Li Ka Shing Foundation Cross-Disciplinary Research Grant (Grant No. 2020LKSFG09A). DFT Computations were performed on the TianHe-2 cluster of Shanxi Supercomputing Center in China.

(1)  Huang, K.; Huang, X.; Nogami, J. Isolated and Assembled Silver Aggregates on the Si(001) Surface: The Initial Stage of Film Formation. Phys. Chem. Chem. Phys. 2021, 23 (7), 4161–4166.

(2)  Huang, X.; Hoffman, A.; Huang, K. Adsorption and Migration of Silver on Group IV Semiconductor (001) Surfaces by Density Functional Theory. J. Phys. Chem. C., 2022, 126 (18), 8134–8142.