Formation of dihydride chains on H-terminated Si(100)-2×1 surfaces: Scanning tunneling microscopy and first-principles calculations

On H-terminated Si(100)-2×1 surface, dihydride chains are often observed along the SB step edge by scanning tunneling microscopy. They are located more than one Si dimer's distance from the step edge. To clarify the reason, we performed first principles calculations on the chain formation process. We found that H termination of the Si surface transforms the rebonded step edge into the combination of a dihydride chain and a nonrebonded step edge. The chain moves away from the step edge by changing positions with the neighboring Si-dimer row. We also investigated the reaction path of this exchange and found that it requires an additional hydrogen atom, which is available during the H-termination process.