ENERGY-DISTRIBUTIONS OF THE REACTION-PRODUCTS FROM GRAPHITE AND B4C DURING ENERGETIC OXYGEN IMPACT

Time-of-flight experiments were performed to determine the energy dist ributions of various reaction products released from graphite and from B4C during 1.5 keV O+ impact. CO from graphite is released in two dis tributions: a thermal energy distribution corresponding to the target temperature and a temperature-independent molecule sputtering distribu tion which can be fitted by a Thompson distribution with an effective surface binding energy of 0.25 eV. At room temperature, the ratio of s puttered CO to thermally released CO amounts to 0.66. In contrast to t his, CO2 is only released thermally. Various boron oxides (BO, BO2, B2 O2, B2O3) are released from B4C. At room temperature, their energy dis tributions can be fitted by Thompson distributions with effective surf ace binding energies between 0.12 and 0.28 eV. With increasing tempera ture an additional thermal distribution appears. Reaction yields publi shed in previous papers were reevaluated with regard to the energy dis tributions reported above.