Formation of Si/Ge nanostructures at surfaces by self-organization

The growth of kinetically self-organized 2D islands in Si/Si(111) epitaxy is described. The island size distribution for this system was measured using scanning tunnelling microscopy (STM). The influence of surface reconstructions on growth kinetics is studied directly using a method of simultaneous deposition and STM scanning. For the case of growth of Si islands on Si(111), lateral growth of rows of the width of the 7 x 7 reconstruction unit cell at the edges of two-dimensional islands leads to the formation of 'magic' island sizes. The evolution of the size and shape of individual {105} faceted Ge islands (hut clusters) on Si(001) is measured during growth. A slower growth rate is observed when an island grows to larger sizes. This behaviour can be explained by kinetically self-limiting growth. The potential formation of thermodynamically stable strained islands of a specific size is discussed. The formation of 2D Si/Ge nanostructures at pre-existing defects is studied. The step flow growth mode is used to fabricate Si and Ge nanowires with a width of 3.5 nm and a thickness of one atomic layer (0.3 nm) by self-assembly. One atomic layer of Bi terminating the surface is used to distinguish between the elements Si and Ge. A difference in apparent height is measured in STM images for Si and Ge. Also different kinds of two-dimensional Si/Ge nanostructure such as alternating Si and Ge nanorings having a width of 5-10 nm were grown.