Formation of convex carbon micro- and nano-disk by atmospheric plasma system

Convex carbon disk growth has been studied by using atmospheric pulsed-DC plasma system. DC voltage was supplied between an Outer cap electrode and an inner electrode which were made by graphite. Convex-shaped carbon disks deposit on (001)Si substrate when the plasma was generated with 10 slm of He flow rate at room temperature. Average diameter of carbon disks was approximately 2-3 mu m and thickness of disk was about 200 nm. It is of interest that diameter of carbon disk did not increase with growth time. In first 5 min, no growth occurs, showing that there is an incubation period prior to the growth of disks. When the Si substrate was positively biased, number of carbon disks deposited on Si substrate decreased. On the other hand, at the negative bias condition, number of disks increases but the shape is distorted in a high bias voltage region (similar to 100 V) maybe due to the ion bombardment effect from the plasma. (C) 2008 Elsevier B.V. All rights reserved.