Reactions of ultrathin hard amorphous carbon (a-C) films under microbeam laser processing

Abstract:  Abstract The decomposition mechanism of hard a-C films under irradiation using a microbeam laser (514.5 nm) was studied. The films were magnetron sputtered at different pressures to achieve different degrees of sp3/sp2 bonding ratio. Under laser irradiation, they showed graphitization and decomposition. The graphitization saturated at early exposure of ?4 min, while the decomposition progressed exponentially with the exposure time, following a first-order reaction mechanism. The decomposition of a-C films under laser irradiation can be modeled using a two-step process with the establishment of a quasi steady-state intermediate. The relative energy barrier and rate constant for film decomposition were calculated. With increasing sp3/sp2 bonding ratio, the films showed increasing resistance against the irradiation-induced changes. This is shown by the decreasing rate constant and increasing energy barrier during the decomposition.