Palladium Hydrogen Sensor with Perfectly Aligned and Highly Uniform Nanogap Arrays

This paper reports a Pd hydrogen gas sensor that uses perfectly aligned uniform nanogap arrays. Depending on the nanogap size, the sensor can differentiate hydrogen concentration thanks to the volume expansion of Pd. The fabrication method of the sensor is based on conventional semiconductor processes; thus, perfectly aligned uniform nanogap arrays can be easily obtained. The standard deviation of the measured nanogap widths was less than 5 nm, and this level of uniformity has not been previously demonstrated in Pd-switching-type sensors. The fabricated sensors with the uniform nanogap array showed abrupt switching characteristics when they were exposed to H2 concentrations over a certain threshold level. Furthermore, based on the unprecedented high uniformity of the nanogap widths, a fine modulation of the threshold level of the H2 concentrations was firstly demonstrated.