This article reports on the growth of Au islands on the Si(111) surface as a function of the Au evaporation rate and the temperature of the surface in ultrahigh vacuum. By controlling the density of the Au islands and their size, it is possible to subsequently grow single vertically oriented Si nanowires on top of (111)-oriented silicon micropillar and analyze their chemical composition at the atomic scale with the femtosecond laser assisted tomographic atom probe. Three-dimensional images of the atom distribution in the nanowire, in particular, the distribution of boron impurities, are obtained and compared to the intended impurity concentration.