Atomic and electronic structures of Ag/Si(100)-c(6 × 2) surface: A first-principles study

Using the experimental data obtained mainly with the scanning tunneling microscopy observations, density functional theory calculations have been applied to examine an atomic structure of the Ag/Si(100)-c(6 × 2) reconstruction. A set of structural models has been proposed having a similar Si(100) substrate reconstruction which incorporates rows of top Si atom dimers and troughs in between the rows. Stability of about twenty models with various Ag coverage ranging from 1/6 to 1 ML has been tested, that allows reducing the number of plausible models to four. Two of these four models have been attributed to the "regular" intrinsic Ag/Si(100)-c(6 × 2) reconstruction, while the other two to its defect-induced modification. The latter is observed in the local areas near defects and domain boundaries and exhibits 3 × 2 periodicity. Comparing the results of calculations with the experimental STM images, it has been concluded that while the Si(100) substrate reconstruction is solid, the Ag subsystem is flexible due to the presence of the lightly bonded mobile Ag atoms.