Oxidising Role of Water Vapour in the 250 Kev D + Induced Radiolysis of Polyimide Kapton-H a)

Residual water vapour present in the vacuum system has been observed to play a dominant oxidising role in the 250 keV D + induced radiolysis of polyimide (Kapton-H). The partial pressure (pp) of water in the vacuum system decreases sharply as the D+ beam impinges the polymeric surface, but soon after, it recovers to its initial value as the accumulated dose increases. Emission of CO 2 is observed which has its maximum at a time when the H 2 O partial pressure is at a minimum. The CO 2 level also returns to its original level with time. This complementary variation of CO 2 and H 2 O confirms that absorbed and adsorbed water molecules are radiolysed by the ion beam and initiate oxidation of the radiolytically evolved CO to yield CO 2 on and within the ion implanted surface of the polyimide. Further, the small enhancement in the 28 amu peak (N 2 + CO), which exhibits no maximum/minimum over the entire implantation time, can be understood in terms of the evolution of N 2 from the imide ring as a result of radiolysis of this nitrogen containing polymers.