Diffraction of swift atoms after grazing scattering from metal surfaces: N/Ag(111) system

Diffraction patterns produced by grazing scattering of fast N atoms from a Ag(111) surface are investigated by employing the surface eikonal approximation. This method is a distorted-wave theory that takes into account the coherent addition of contributions coming from different projectile paths. In the model the projectile-surface potential is obtained from an accurate density-functional theory calculation. The dependence of the scattered projectile spectra on impact energy and incidence channel is analyzed, and possible incident direction and energy range for the observation of the interference patterns are predicted. In addition, it is found that as a result of the high reactivity of N atoms, asymmetries of the surface potential might be detected through their effects on diffraction patterns.

Figure 1

Schematic depiction of the elastic collision process and the coordinate system.

Figure 2

Azimuthal angular distribution of elastic scattered projectiles for 3-keV N atoms impinging on Ag(111) along the direction $\langle \overline{1},\overline{1},2\rangle$, with the incidence angle ${\theta }_i=0.{47}^{°}$. The perpendicular energy, evaluated as explained in the text, is 0.2 eV.

Figure 3

Angular projectile distributions, as function of the deflection angle $\Theta$, for N atoms scattered from Ag(111) along the direction $\langle \overline{1},\overline{1},2\rangle$, with $E_{i\perp }=$ 0.5 eV. Two different incidence energies are considered: solid line, $E_i=$ 3.0 keV; and dashed line, $E_i=$ 7.0 keV.

Figure 4

Similar to Fig. 3 for 3-keV N atoms impinging with the perpendicular energy $E_{i\perp }=$ 1.0 eV.

Figure 5

Similar to Fig. 4 for scattering along the direction $\langle \overline{1},0,1\rangle$, with $E_{i\perp }=$ 0.2 eV.

Figure 6

(a) Surface geometry and symmetry. Symbols indicate the $\mathit{XY}$ grid, with TOP, HCP, and FCC points placed on top of Ag atoms of the first, second, and third layers, respectively. (b) Energy difference between PES values at HCP and FCC positions, as a function of the distance $Z$ to the topmost atomic layer.