Nanogap-controlled Pd coating for hydrogen sensitive switches and hydrogen sensors

Abstract

We present a simple and facile method for producing high-performance hydrogen (H2) sensors based on vertically ordered metal-oxide nanorods with a Pd films on a 4-inch SiO2/Si substrate by a glancing-angle deposition. Firstly, optimal density of nanorods was formed by changing an incident angle of vapor flux. Secondly, nanogaps between each nanorod were precisely controlled by manipulating thickness of Pd films. At room temperature in ambient air, 15-nm-thick Pd-coated SiO2 nanorods showed the rapid on-off switches. The average response time was approximately 2.8 s (the longest response time: 5 s), and the recovery time was less than 1 s for 2%–0.8% H2. For 20-nm-thick Pd-coated SiO2 nanorods, detection of limit was reduced to 10 ppm due to semi-on-off operation. The reproducibility of our approaches was investigated by fabricating the Pd-coated SnO2 nanorods. They also exhibited the high H2 sensing performance as Pd-coated SiO2 nanorods. We strongly believe that high H2 sensing performance of Pd nanogap controlled metal oxide nanorods provides a new perspective for room-temperature H2 switches and sensors based on H2-induced lattice expansion.