We report on the hydrogen gas (H 2 ) sensing performance of lithographically patterned Pd nanowires as a function of the nanowire thickness and H 2 concentration. A combination of electron-beam lithography and a lift-off process has been utilized to fabricate four-terminal devices based on individual Pd nanowires with width w = 300 nm, length l = 10 νm, and thickness t = 20-400 nm from continuous Pd films. The variation of the resistance and sensitivity at 20 000 ppm H 2 of Pd nanowires was found to be much lager than at 10 000 ppm H 2 , which can be explained by an α-β phase transition occurring at 20 000 ppm H 2 . This is confirmed by the observation of hysteresis behavior in the resistance versus H 2 concentration for Pd thin films. The response time was found to decrease with decreasing thickness regardless of H 2 concentration due to a higher surface-to-volume ratio and a higher clamping effect. A single Pd nanowire with t = 100 nm was found to successfully detect H 2 at a detection limit of 20 ppm. Our results suggest that lithographically patterned Pd nanowires can be used as hydrogen gas sensors to quantitatively detect H 2 over a wide range of concentrations.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering
- Electrical and Electronic Engineering