Hydrogen absorption/desorption behavior with oxygen-contaminated boron film

Abstract

The effect of oxygen contamination on hydrogen absorption and desorption behavior from a boron coating film has been studied. Oxygen atoms were implanted by glow discharge in an O 2/He gas mixture until near saturation, into the boron film deposited by PCVD. The depth profile measurement by AES showed that O atoms were retained up to the depth of 20 nm. Hydrogen discharges were carried out to investigate the H absorption behavior. The capability of H absorption decreased for 30–50% compared to the pure boron film without O contamination. After the discharge, the depth profile of the oxygen atoms was not changed, which means that a stable oxide layer had formed. The reduction of the H absorption capability occurs probably because the formation of the boron oxide prevents H atoms from trapping in the form of B–H bonding. Most of the retained H atoms can be released by a heating up to 500°C with the O contamination. The required temperature for H evacuation is slightly higher than that for pure boron film. In addition, a small peak was observed at around 200°C. From these results, the applicability of boronization to future long term discharges was discussed, in which the boron film saturates with O contamination.