Ge quantum dots on a large band gap semiconductor: the first growth stages on 4H–SiC(0 0 0 1)

The Ge growth on SiC(0 0 0 1) follows a Stranski–Krastanov mode for Si-rich (3×3) and View the MathML source reconstructed surfaces. For Ge deposit in particular temperature conditions, a new (4×4) superstructure takes place and the reflection high energy electron diffraction (RHEED) specular spot intensity presents one oscillation proving a wetting layer formation. An island nucleation is then ascertained by the oscillation vanishing and by the appearance of a k⊥-modulated RHEED pattern. On the other hand, on a View the MathML source C-rich surface, a direct Ge island nucleation is observed from the first growth stage. Indeed, for View the MathML source Ge, the RHEED diagram consists in spots and rings, and the atomic force microscopy analysis indicates a high density (View the MathML source) of small islands (View the MathML source, View the MathML source). The RHEED spot analysis shows a preferential epitaxial relationship with the substrate Ge(1 1 1)//SiC(0 0 0 1). The Ge–C bonding being energetically unfavourable, Ge tends to form islands immediately rather than wetting the graphite-terminated surface. The Ge growth mode on C-rich surface is thus of Volmer–Weber type.