Kinetically Induced Kinking of Vapor-Liquid-Solid Grown Epitaxial Si Nanowires

Epitaxial Si nanowires grown from Au seeds using the vapor-liquid-solid method begin growing normal to the Si(111) substrate atop a tapered base. After a kinetically determined length, the NWs may kink away from [111] to another crystallographic direction. The smallest NWs prefer growth along < 110 > while larger Si NWs choose either < 111 > or < 112 > based on whether growth conditions favor Au-free sidewalls. Vertical growth normal to the Si(111) substrate is obtained only for slowly growing NWs with Au-decorated sidewalls. At the fastest growth rates, single-crystal Si NWs smoothly, continuously, and randomly vary their growth directions, producing a morphology that is qualitatively different than highly kinked growth.