First-principles study of Ag adsorption on the H-passivated Si(001) surface with Bi nanolines

This first-principles study examines the adsorption and migration of Ag atoms on the H-passivated Si(001) surface with Bi nanolines, and finds that Ag nucleates preferentially at the nanolines in the following manner. An Ag atom deposited on the H-passivated surface rapidly migrates through a groove between dimer rows (the barrier is 0.14 eV), to reach a Bi nanoline. Then, the adatom enters a backbond of the Bi nanoline, bonding directly to Si and releasing the energy of similar to 0.7 eV. After that, the adatom migrates along the nanoline (the barrier is 0.33 eV), and encounters another adatom to form a dimer, without leaving the backbonds. The dimer is sufficiently stable at room temperature (dissociation energy is 1.0 eV) to serve as a growth nucleus. Thus, Ag nucleates preferentially at the Bi nanolines, directly on Si.