DEGRADATION OF POLYIMIDE BY IMPLANTATION WITH AR+ IONS

Polyimide (PI) samples were irradiated with 200 keV Ar+ ions to fluenc es from 5 x 10(13)-1 x 10(17) cm(-2) and the concentration depth profi les of implanted Ar atoms as well as of carbon and oxygen atoms of the polymer matrix were determined using the Rutherford backscattering te chnique. The surface polarity, sheet resistivity, and thermoelectric p ower of PI samples were also determined as a function of the ion fluen ce and temperature. As a result of the ion irradiation, the polyimide surface layer is depleted of oxygen and enriched by carbon. The sheet resistivity exhibits a minimum at the ion fluence of 5 x 10(16) cm(-2) and the temperature dependence of the sheet resistivity indicates the semiconducting character of irradiated PI and the variable range hopp ing mechanism of charge transport. The thermoelectric power of the PI samples irradiated to high fluences is small, of the order of mu V/K, and independent of temperature. This behavior is typical for metals. T he simultaneous appearance of metal and semiconducting properties is p robably due to the complex structure of the PI surface layer modified by the ion irradiation. (C) 1997 John Wiley & Sons, Inc.