Atomic hydrogen flux density measured using thin metal films

Abstract

Using one-or two-layer films of transition metals, it is possible to determine the atomic hydrogen flux density under reduced gas pressure conditions (10−1–10−3 Pa). The method consists in monitoring a change in the film resistance caused by selective dissolution of atomic hydrogen in the metal during exposure of the film in a mixed atomic-molecular flow, followed by determining a characteristic time τ required for the hydrogen concentration in the film to reach 63% of the maximum possible level. The hydrogen flux density is then calculated within the framework of a simple mathematical model of the film saturation with hydrogen described by a relaxation law. The proposed method is characterized by a high selective sensitivity to atomic hydrogen. The atomic hydrogen flux density in a mixed atomic-molecular flow can be determined in a range from 5×1013 to 1016 cm−2 s−1.