Radial growth dynamics of nanowires

In this brief paper, wt: address the problem of the radial growth dynamics of a nanowire due to the vapor-solid (VS) process while at the same time it grows along its axial direction due to vapor-liquid-solid (VLS) process. We show that there exists a critical radius at a certain saturation and that the nanowire will thicken if its initial radius is larger than the critical radius and vice versa. Only when its initial radius is equal to the critical radius will the radius of the nanowire be uniform along its axial direction. In all other cases, the nanowire is tapered with a certain slope. The slope is relevant to the initial radius. The closer it is to the critical radius, the smaller is the slope and vice versa. Although the slope may be generally very small, it still does exist. This suggests that it is difficult to grow long nanowires with a uniform radius. (C) 2001 Published by Elsevier Science B.V.