First-principles study ofNH3decomposition on the Si(001) surface

Abstract

We present first-principles density-functional calculations for ${\text{NH}}_{3}$ decomposition on the Si(001) surface. Our calculations show that the dissociated NH (or N) species inserted into the dimer bond is thermodynamically favored over that inserted into the back bond of the Si dimer. However, $\mathrm{N}$ interdiffusion from the former configuration to a recently observed ${\text{Si}}_{3}\ensuremath{\equiv}\mathrm{N}$ configuration (where the $\mathrm{N}$ atom is incorporated at an interstitial site around the third layer) is kinetically prohibited because of the existence of a high activation barrier. On the other hand, there is a relatively lower-energy barrier from the latter configuration, leading to formation of the ${\text{Si}}_{3}\ensuremath{\equiv}\mathrm{N}$ configuration. This kinetics of $\mathrm{N}$ interdiffusion is consistent with the proposed reaction path from a recent high-resolution core-level photoemission spectroscopy data.