Hydrogen sensors: Role of palladium thin film morphology

The effect of thin film morphology, carbon monoxide (CO) and resistor geometry on the response of hydrogen sensitive thin film palladium resistors has been investigated. Films with two different morphologies were fabricated by DC magnetron sputtering under different gas pressures. Palladium thin film morphology was found to strongly influence sensor response in terms of hydrogen sensitivity and rate of response. In dense columnar Pd films, CO dramatically increases the time-lag in sensor response to H2 in H2/CO mixtures. However, the steady state value of the response remains unchanged. Films with a void filled columnar morphology exhibited shorter time-lag in response to H2 in presence of CO.