Deciphering the Atomistic Mechanism of Si(111)-7 × 7 Surface Reconstruction Using a Machine-Learning Force Field
Abstract
While the complex 7 × 7 structure that arises upon annealing the Si(111) surface is well-known, the mechanism underlying this unusual surface reconstruction has remained a mystery. Here, we report molecular dynamics simulations using a machine-learning force field for Si to investigate the Si(111)-7 × 7 surface reconstruction from the melt. We find that there are two possible pathways for the formation of the 7 × 7 structure. The first path arises from the growth of a faulted half domain from the metastable 5 × 5 phase to the final 7 × 7 structure, while the second path involves the direct formation of the 7 × 7 reconstruction. Both pathways involve the creation of dimers and bridged five-membered rings, followed by the formation of additional dimers and the stabilization of the triangular halves of the unit cell. The corner hole is formed from the joining of several five-member rings. The insertion of atoms below the adatoms to form a dumbbell configuration involves extra atom diffusion or rearrangement during the evolution of triangular halves and dimer formation along the unit cell boundary. Our findings may provide insights for manipulating the surface structure by introducing other atomic species.
Copyright and License
© 2023 American Chemical Society.
Acknowledgement
Y.S. and Q.A. were supported by NSF (CMMI-2019459). W.A.G. thanks the Hong Kong Quantum AI Lab, AIR@InnoHK of Hong Kong Government, for support. The authors would like to acknowledge and thank Dr. Joseph E. Demuth for useful discussions and significant contributions to this work.
Conflict of Interest
The authors declare no competing financial interest.
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Additional details
- ISSN
- 1520-5126
- National Science Foundation
- CMMI-2019459
- Government of Hong Kong