Effects of Shadowing in Oblique-Incidence Metal (100) Epitaxial Growth

The effects of shadowing in oblique-incidence metal (100) epitaxial growth are studied using a simplified model. We find that many of the features observed in Cu(100) growth, including the existence of a transition from anisotropic mounds to ripples perpendicular to the beam, can be explained primarily by geometrical effects. We also show that the formation of (111) facets is crucial to the development of ripples at large angles of incidence. A second transition to “rods” with (111) facets oriented parallel to the beam is also found at high deposition angles and film thicknesses.

Figure 1

(a) Surface roughness (in ML) as function of film thickness for $\theta =0°–88°$ for case of slow deposition and moderate ES barrier with $L=512$. Error bars (not shown) are just slightly larger than line thickness. (b) Relative width deviation $\delta w/w(t,0)$ as function of scaled deposition angle $\theta t^{\gamma }$ for $\theta =10°–88°$ and $t=5–100$ ML for three different cases: fast deposition, high ES barrier (top), fast deposition moderate ES barrier (middle), and slow deposition, moderate ES barrier (bottom).

Figure 2

Grayscale pictures of surface morphology ($512\times 512$ portion of $L=2048$ system) for same conditions as in Fig. 1a at $t=50$ ML. Arrow indicates deposition direction. Inset shows ripple profile taken along line in (b).

Figure 3

Anisotropy $\alpha ={\xi }_{\perp }/{\xi }_{\parallel }$ as a function of film thickness for the case of slow deposition with a moderate ES barrier. (a) Multilayer regime with $L=2048$; (b) submonolayer regime with $L=512$. In (b) the corresponding results for a large ES barrier are also shown (open symbols).

Figure 4

Scaled correlation length ${\xi }_{\perp }/t^{2\gamma }$ as function of scaled deposition angle for three different sets of deposition parameters: (a) fast deposition, large ES barrier, (b) fast deposition, moderate ES barrier, and (c) slow deposition, moderate ES barrier.