Physical consequences of the equivalence of conditions for the steady-state growth of nanowires and the nucleation on triple phase line

Abstract

A new theoretical model describing the steady-state growth and crystalline structure of semiconductor nanowires (NWs) is proposed and its physical consequences are considered. It is demonstrated that the Nebol’sin-Shchetinin condition (nonwetting of the NW side surface by the liquid drop) necessary for the steady-state growth of NWs according to the vapor-liquid-solid (VLS) mechanism is equivalent to the Glas condition of nucleation on the triple phase line for the monocentric NW growth. An energy criterion for the steady-state growth of NWs is formulated in the general case of faceted NW side surface. Effective surface energies are found that determine the activation barrier for nucleation at the NW top. Based on the proposed model, the issue of determining the III–V semiconductor NW crystal structure (cubic zinc blende type versus hexagonal wurtzite type) is considered. In particular, it is shown that a decrease in the surface energy of a catalyst must lead to the predominant formation of a cubic phase, which is confirmed by experimental data on the growth of GaAs nanowires according to the VLS mechanism with Au and Ga catalysts.