Growth of Si on Ag(111) and determination of large commensurate unit cell of high-temperature phase

We studied the structural transition for silicon adsorption on Ag(111) by using low-energy electron diffraction (LEED) and Auger electron spectroscopy at various substrate temperatures during deposition. We obtained a single phase of the (4 × 4) structure at 520 K, which was reported as a silicene. At 620 K, the (4 × 4) structure changed to a high-temperature phase which was determined as ( √133 × √133) R 4.3° by LEED, while in preceding works, it was assigned to a quasi (2√3 × 2√3) R 30° or (3.5 × 3.5) R 26° structure. Although the high-temperature phase had not been observed as a single phase, we obtained LEED patterns with a single phase for it, which enabled us to explain all the diffraction spots on the basis of the kinematic theory including double diffraction. The (√133 × √133) R 4.3° was obtained by the multiplication of a (1.35 × 1.35) R 9.9° subunit cell. We concluded that the (2 √3 × 2√3) R 30° and (3.5 × 3.5) R 26° phases could instead be represented as a ( √133× √133) R 4.3° phase, and we proposed a possible atomic model.