Behavior of hydrogen atoms in boron films during H 2 and He glow discharge and thermal desorption

Abstract

Hydrogen absorption and desorption characteristics in boron films deposited on a graphite liner have been studied. The number of hydrogen atoms absorbed in the films is estimated from a decrease in hydrogen pressure during a hydrogen glow discharge. It was 1.9 × 10 17 atoms cm 2 in the 1 h discharge after an evacuation of H atoms contained in the original boron films by thermal desorption. Hydrogen atoms were absorbed continuously without saturation for 3 h during the discharge. The number of H atoms absorbed reached 2.6 × 10 17 atoms cm 2 at 3 h. A discharge in helium was carried out to investigate H desorption characteristics from hydrogen implanted boron films. It was verified that capacity for hydrogen absorption was recovered after the He discharge. Hydrogen atoms were accumulated in the films by repetition of alternate He and H 2 discharge. Thermal desorption experiments have been carried out by raising the liner temperature up to 500 °C for films after 1 h, 3 h hydrogen discharge and 6 times repetition of H 2 He discharges. Most of the H atoms in the films were desorbed for all these cases. The slow absorption process was confirmed through the thermal desorption experiments.