The initial surface roughening during Ge epitaxy on Si(001) is shown to arise from an effective repulsion between S(A) surface steps and dimer vacancy lines (VLs). This step-VL interaction gradually inactivates a substantial fraction of adatom attachment sites at the growth front, causing a rapid increase in the rate of two-dimensional island nucleation. The mutual repulsion hinders the crossing of S(A) surface steps over VLs in the second layer, thus organizing the developing surface roughness into a periodic array of anisotropic 2D terraces. Isolated (105) facets forming at specific sites on this ordered template mediate the assembly of first 3D Ge islands.

Transmission through an opaque Au film with a single subwavelength aperture centered in a smooth cavity between linear grating structures is studied experimentally and with a finite element model. The model is in good agreement with measured results and is used to investigate local field behavior. It shows that a surface plasmon polariton (SPP) is launched along the metal surface, while interference of the SPP with the incident light along with resonant cavity effects give rise to suppression and enhancement in transmission. Based on experimental and modeling results, peak location and structure of the enhancement/suppression bands are explained analytically, confirming the primary role of SPPs in enhanced transmission through small apertures in opaque metal films.

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