Energy distributions of the reaction products from graphite and B 4C during energetic oxygen impact

Abstract

Time-of-flight experiments were performed to determine the energy distributions of various reaction products released from graphite and from B 4C during 1.5 keV O + impact. CO from graphite is released in two distributions: a thermal energy distribution corresponding to the target temperature and a temperature-independent molecule sputtering distribution which can be fitted by a Thompson distribution with an effective surface binding energy of 0.25 eV. At room temperature, the ratio of sputtered CO to thermally released CO amounts to 0.66. In contrast to this, CO 2 is only released thermally. Various boron oxides (BO, BO 2, B 2O 2, B 2O 3) are released from B 4C. At room temperature, their energy distributions can be fitted by Thompson distributions with effective surface binding energies between 0.12 and 0.28 eV. With increasing temperature an additional thermal distribution appears. Reaction yields published in previous papers were reevaluated with regard to the energy distributions reported above.