THE AREA OF CARBON SURFACES MODIFIED BY O2 PLASMA THROUGH A NARROW GAP

When carbon materials of various shapes are treated by plasmas, it is problem which area of the carbon surfaces is modified and whether the surface is modified uniformly or not. In order to investigate the modified area in this case, we treated the sample which is a cavernous box having a hole. The material of various shapes is simplified in the sample of this shape. This sample consists of two carbon plates and a spacer. The specimen, spacer and source gas used in this experiment were glassy carbon(GC, 25×50mm), aluminum and O2, respectively. The thickness of the spacer, equal to the gap of the GC plates, were variable from 0.5mm to 5mm. Property of the inner surface of the GC plate was estimated using the contact angle of water, its elapsed change and SEM photographs. The contact angle before treatment was about 90°. When the hole was 1mm in diameter and the gap d between the GC plates was 0.5mm, the contact angle near the center of the inner surface of the GC plate was 38°, and one at the term was 90°: only the area near the center was modified. With 5mm of the gap d, the contact angle at any place of the GC plates was constant at the value of 32°: all over the inner surface was modified uniformly. The degree of the surface modification in the sample (box) depends on the condition of the generation and removal of the modification sources formated by the plasma.