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

Abstract

Kinetics and mechanisms of laser-induced decompositions of hydrogenated amorphous carbon films on magnetic hard disksThe decomposition mechanism of hard a-C films under irradiation using a microbeam laser ͑514.5 nm͒ was studied. The films were magnetron sputtered at different pressures to achieve different degrees of sp 3 / sp 2 bonding ratio. Under laser irradiation, they showed graphitization and decomposition. The graphitization saturated at early exposure of ϳ4 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 sp 3 / sp 2 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.