Production of Trapped Deuterium via Deuteron-Cathode Bombardment in a DC Glow Discharge

A simple deuterium DC glow discharge was employed to study the production of densely packed deuterium clusters with high binding energies in palladium. The incident ions create damage cascades leading to the production of defects such as vacancies, dislocations, and voids. These defects trap interstitial deuterons with binding energies dependent on the trap’s geometry and volume. 1 Varying fluences of incident ions were used (1E18 ions/cm 2 , 1E19 ions/cm 2 , and 1E20 ions/cm 2 ) and incident energies dependent on cathode bias (-0.75 kV, -0.875 kV, and -1.0 kV). Thermal Desorption Spectroscopy (TDS) was used to estimate the clusters’ trapping energies. 2 There appeared to be a deuterium trapping limit dependent on defect concentration where once a distinct defect density was met any further damage was counterproductive in deuterium trapping. The condition that produced the most trapped deuterium was -0.75 kV in 1 Torr deuterium with a fluence of 1E18 ions/cm 2 . Some samples were observed under SEM and TEM. The results showed surface pit and blister formations which grew in concentration as the fluence increased. Beneath the surface formations, cross-section images showed large voids and holes in the material with cracks at grain boundaries. TEM images displayed the resulting damage structure which extended ~250 nm into the cathode for a sample at 1.0 Torr and -1.0 kV. A proposal is that as the damage concentration increased, these voids grew to such an extent that they formed the blisters and eventually ruptured.