About a Fundamental Uncertainty of the Contact Angle of the Catalyst Drop on the Top of the Nanowire

In this paper we developed the concepts about the crystallization processes occurring near the three phase boundary and the conditions of equilibrium wetting of nanowire (NW) surface with a catalyst liquid drop characterized by the contact angle. We demonstrated that the fundamental uncertainty in the contact angle of the saturated catalyst drop at the top of the NWs is due to the interaction of two opposing competing processes: the spheroidization of the catalytic liquid during the gravity neutralization and the wetting. We proposed a method to determine the free energy of the phase boundaries by the shape of a metal catalyst drop on the top of the NWs as well as on the substrate. The paper also presents the results of obtaining the interphase free energy of the boundaries in Si-Au, Si-Cu, Ge-Au, GaAs-Au, InAs-Au, SiC-Fe, InP-Au, etc. systems.