A Pt/oriented-C hydrogen gas sensor

A Pt/C heterojunction has been fabricated and tested as a conductometric hydrogen gas sensor. The carbon layer, deposited between planar Au substrate contacts using a filtered cathodic vacuum arc (with an applied substrate bias of -500 V), consisted largely of vertically oriented graphitic sheets. These sheets have good through-film electrical conductivity and contributed to a low device resistance of ~60 ¿. The Pt layer (of 3 nm thickness) was deposited using a Gatan Model 682 Precision Electron Coating System (PECS). A change in the device resistance of >2% was exhibited upon exposure to 1% hydrogen gas (in synthetic, zero humidity air) at room temperature. The time for the sensor resistance to decrease by 2% under these conditions was 60 s and the baseline (zero hydrogen exposure) resistance remained constant to within 0.03% during and after the exposure tests.