The Role of Surface Energies and Chemical Potential during Nanowire Growth

We present an approach to quantitatively determine the magnitudes and the variation of the chemical potential in the droplet (Delta mu), the solid liquid (gamma(SL)) and the liquid-vapor (gamma(LV)) interface energies upon variation of the group III partial pressure during vapor-liquid-solid growth of nanowires. For this study, we use GaP twinning superlattice nanowires. We show that gamma(LV) is the quantity that is most sensitive to the Ga partial pressure (p(Ga)), its dependence on p(Ga) being three to four times as strong as that of gamma(SL) or Delta mu, and that as a consequence the surface energies are as important in determining the twin density as the chemical potential. This unexpected result implies that surfactants could be used during nanowire growth to engineer the nanowire defect structure and crystal structure.