Anew hydrogen sensor utilizing plasma-enhanced chemical vapor deposited diamond inconjunction with palladium(Pd) metal has been developed. The device isfabricated in a layered Pd/undoped diamond/p-doped diamond Schottkydiode configuration. Hydrogensensing characteristics of the device have been examined in termsof sensitivity, linearity,response rate, and response time as a functionof temperature and hydrogen partial pressure. Hydrogen adsorption activation energyis investigated in the temperature range from 27 to 85°C.Analysis of the steady-state reaction kinetics usingthe I-V method confirmthat the hydrogen adsorption process is responsible for the barrierheight change in the diamondSchottky diode. The ability to fabricatediamond-based hydrogen sensor on a variety of substrates makes thedevice veryversatile for gas sensing.