Hydrogen gettering of titanium-palladium/palladium nanocomposite films synthesized by cosputtering and vacuum-annealing

Abstract

Nano-engineered composite film, prepared by the combination of titanium (Ti) nanoparticles with surrounding layers of palladium (Pd), has been suggested as a high performance hydrogen (H-2) getter. Uniform Ti Pd film covered by a 35-nm-thick Pd layer was deposited on a silicon wafer via cosputtering and post-vacuum-annealing. As the annealing temperature increased from 200 to 400 degrees C, amorphous alloy and nano-aggregates were observed, and efficient structural modulation occurred at 400 degrees C, where dewetting of Pd cover layer from the getter surface was observed. This led to the enhancement of the chemisorption capacity of the 400 degrees C-annealed sample, two-times higher than that of the 300 degrees C-annealed sample. Abrupt change in residual gases, which typically come from a bonding process, can be mitigated by minimizing the gas transfer distance through the dewetting of the cover layer; since Ti nanoparticles surrounded by Pd exist independently of each other in the gettering layer, external H-2 gas molecules can be continuously adsorbed onto still-unreacted Ti particles by passing through the dewetted channels in the Pd cover layer. This concept demonstrates a pathway towards a useful synthetic approach for high-performance thin-film getters with high adsorption capacity, fast gettering rate and good device compatibility. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.