Metallization of the Si(001) surface: An atomistic study using a neural network potential

Despite being one of the widely studied surfaces because of its technologically importance, the nature of the metallization of Si(001) at high temperatures is still an open question. The semiconductor-metal transition of the surface occurring at 900 K is often linked to the transformation from asymmetric to symmetric structure of the Si dimers at the surface [1]. In this work, we apply a neural network derived interatomic potential to perform molecular dynamics simulations of Si(001) for a large temperature range. This potential was developed with input from ab initio molecular dynamics simulations of Si(001) and validated to be as accurate as density functional theory. Our simulations show that the asymmetric, buckled structure of the dimer still exists at higher temperatures, but the increased dimer flipping rate makes them spend more time in the symmetric configuration making the surface metallic. Our results also suggested that such phenomenon is appreciable even at temperatures lower than 900 K, in agreement with angle-resolved photoemission spectroscopy data [2].

[1] Y. Fukaya and Y. Shigeta, Phys. Rev. Lett. 91, 126103 (2003).
[2] C. Jeon et al, Phys. Rev. B 80, 153306 (2009).