26 February 2001 Stabilizing the response of Pd/Ni alloy films to hydrogen with Ti adhesion layers
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Proceedings Volume 4205, Advanced Environmental and Chemical Sensing Technology; (2001) https://doi.org/10.1117/12.417437
Event: Environmental and Industrial Sensing, 2000, Boston, MA, United States
Abstract
We have studied catalytic thin film resistors made from a Pd and Ni alloy, and propose a method for dramatically reducing the drift of the measured resistance. The resistances of Pd films increase monotonically when exposed to hydrogen, however a stable baseline is difficult to achieve and alpha to beta phase transitions result in hysteresis. It is known that at high hydrogen concentrations, the Pd film cracks and delaminates, however long-term exposures to low concentrations of hydrogen can also result in delaminations. Studies using Pd/Ni alloys show that the phase transition can be suppressed. High temperature anneals in 2 % hydrogen, and the addition of a Ti adhesion layer is shown to reduce drift. Usually long term studies on films are conducted in an ordinary air (oxidizing) atmosphere; however, we report here on studies carried out in a reducing atmosphere of 0.1% hydrogen in nitrogen for 6 months on two sensor structures, field effect transistors (FETs) and resistors. The Sandia Robust Hydrogen Sensor platform containing integrated heaters, temperature sensors, and hydrogen sensitive resistors and FETs was compared to a Sandia Wide Range Sensor containing a 10 atomic percent Ni/Pd (1000Å) alloy resistor with a (100Å) Ti adhesion layer. After six months the two hydrogen sensing resistors on the Robust platform, without an adhesion layer, read a hydrogen concentration of 61% and 2.3%, while the Wide Range Sensor read a hydrogen concentration of 0.102%, which is a dramatic improvement in limiting baseline drift.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mark W. Jenkins, Robert C. Hughes, Sanjay V. Patel, "Stabilizing the response of Pd/Ni alloy films to hydrogen with Ti adhesion layers", Proc. SPIE 4205, Advanced Environmental and Chemical Sensing Technology, (26 February 2001); doi: 10.1117/12.417437; https://doi.org/10.1117/12.417437
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