A team at Osaka University has invented a new process for creating high-precision sensing devices that respond to the presence of hydrogen gas. By carefully controlling the deposition of metallic nanoparticles on a silicon surface, the researchers were able to create a sensor that can detect low levels of hydrogen on the basis of changes in electrical current. This research may have important benefits as part of a switch to hydrogen-based fuels, which could power the zero-emission cars of the future and help fight anthropogenic climate change.
To fabricate a hydrogen sensor, the researchers deposited metallic palladium on a silicon substrate. The deposited palladium forms nanoparticles on the substrate, and they act like tiny islands that are excellent conductors of electricity, but, because they do not form a connected network, the current across the device is very small.
However, when hydrogen atoms are present, they are absorbed into the palladium nanoparticles, increasing volume of the nanoparticles, and then bridge the gaps between the islands. Eventually, a completely connected path is formed, and electrons can flow with much less resistance. In this way, even a tiny change in hydrogen concentration can lead to a massive increase in current, so the devices can be made very sensitive.