Surface analysis of plasma-treated polydimethylsiloxane by x-ray photoelectron spectroscopy and surface voltage decay

Surface states of polydimethylsiloxane (PDMS) treated by plasma were investigated by x-ray photoelectron spectroscopy and surface voltage decay. X-ray photoelectron spectroscopy confirmed the formation of a silica-like (SiOx, x = 3-4) oxidative surface layer. This layer increased in thickness with increasing exposure duration of plasma. Plasma exposure lowers the surface resistivity from 1.78 x 10(14) to 1.09 x 10(13) Omega rectangle(-1) with increasing plasma treatment time. By measuring the decay time constant of surface voltage, the calculated surface resistivity was compared with the value measured directly by a voltage-current method; good agreement between the two methods was obtained. It was observed that plasma treatment led to a decrease in the thermal activation energy of the surface conduction from 31.0 kJ mol(-1) for an untreated specimen to 21.8 kJ mol(-1) for a plasma-treated specimen for 1 h. Our results allow the examination of effects of plasma on the electrical properties of PDMS. Copyright (C) 2003 John Wiley Sons, Ltd.