Atomic structure of metal-free and catalyzed Si nanowires

Metal-free and Au-catalyzed silicon nanowires (Si-NWs) grown at low temperatures have been analyzed through transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and their crystalline phase studied. All the observed nanowires are crystalline, grow along two different directions, ?110? or ?112?, and contain high density of planar defects, such as stacking faults (SFs) and twins. The defect size is comparable to the wire diameter for the metal-free process whilst it is much larger than the wire diameter for the Au-catalyzed Si-NWs. In this latter case parallel SFs may re-arrange and transform in a metastable rhombohedral 9R polytype structure whose formation mechanism is discussed. © 2011 Materials Research Society.