Spontaneous, Defect-Free Kinking via Capillary Instability during Vapor–Liquid–Solid Nanowire Growth

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• 作者：Yanying Li ; Yanming Wang ; Seunghwa Ryu ; Ann F. Marshall ; Wei Cai ; Paul C. McIntyre
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：March 9, 2016
• 年：2016
• 卷：16
• 期：3
• 页码：1713-1718
• 全文大小：353K
• ISSN：1530-6992

文摘

Kinking, a common anomaly in nanowire (NW) vapor–liquid–solid (VLS) growth, represents a sudden change of the wire’s axial growth orientation. This study focuses on defect-free kinking during germanium NW VLS growth, after nucleation on a Ge (111) single crystal substrate, using Au–Ge catalyst liquid droplets of defined size. Statistical analysis of the fraction of kinked NWs reveals the dependence of kinking probability on the wire diameter and the growth temperature. The morphologies of kinked Ge NWs studied by electron microscopy show two distinct, defect-free, kinking modes, whose underlying mechanisms are explained with the help of 3D multiphase field simulations. Type I kinking, in which the growth axis changes from vertical [111] to ⟨110⟩, was observed in Ge NWs with a nominal diameter of ∼20 nm. This size coincides with a critical diameter at which a spontaneous transition from ⟨111⟩ to ⟨110⟩ growth occurs in the phase field simulations. Larger diameter NWs only exhibit Type II kinking, in which the growth axis changes from vertical [111] directly to an inclined ⟨111⟩ axis during the initial stages of wire growth. This is caused by an error in sidewall facet development, which produces a shrinkage in the area of the (111) growth facet with increasing NW length, causing an instability of the Au–Ge liquid droplet at the tip of the NW.