Silicon nanowires have been grown in a horizontal tube furnace by disproportionation of silicon monoxide in combination with the vapor-liquid-solid mechanism. We present a phase diagram of the nanowire growth, indicating different morphologies for varying growth pressure and temperature. The morphology was characterized by scanning electron microscopy and detailed structural analysis was performed by transmission electron microscopy. A variety of morphologies is found and the optimum parameter range for the growth of straight and uniform nanowires consisting of crystalline silicon cores and amorphous SiO2 shells is identified and discussed. (C) 2010 Elsevier B.V. All rights reserved.