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

Abstract

The growth of kinetically self-organized 2D islands in Si/Si(111) epitaxy is described. Theisland size distribution for this system was measured using scanning tunnelling microscopy(STM). The influence of surface reconstructions on growth kinetics is studieddirectly using a method of simultaneous deposition and STM scanning. For the caseof growth of Si islands on Si(111), lateral growth of rows of the width of the7 × 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 Geislands (hut clusters) on Si(001) is measured during growth. A slower growth rate isobserved when an island grows to larger sizes. This behaviour can be explained bykinetically self-limiting growth. The potential formation of thermodynamically stablestrained islands of a specific size is discussed. The formation of 2D Si/Ge nanostructures atpre-existing defects is studied. The step flow growth mode is used to fabricate Si and Genanowires with a width of 3.5 nm and a thickness of one atomic layer (0.3 nm) byself-assembly. One atomic layer of Bi terminating the surface is used to distinguish betweenthe elements Si and Ge. A difference in apparent height is measured in STMimages for Si and Ge. Also different kinds of two-dimensional Si/Ge nanostructuresuch as alternating Si and Ge nanorings having a width of 5–10 nm were grown.