DISSOCIATIVE ADSORPTION OF NH3 ON SI(001)-(2X1)

Using the first-principles pseudopotential-local-density-approximation approach. we have studied the dissociative molecular adsorption of NH 3 on Si(001)-(2 x 1). We find that upon adsorption the Si dimer become s symmetric and somewhat elongated. We also find that the Si-N bond is inclined at 10 degrees with respect to the surface normal, the N-Si b ond length is 1.75 Angstrom, and the N-H bond length is 1.05 Angstrom. Finally, our electronic structure calculations suggest that the adsor ption of ammonia almost completely passivates the silicon surface. [S0 163-1829(98)05636-7].