Significance of electrode-spacing in hydrogen detection for tin oxide-based MEMS sensor

“Nano-Macro” and “Nano-Micro” integrated sensor-devices have been fabricated via sol–gel dip-coating the nanocrystalline indium oxide ( In 2 O 3 ) -doped tin oxide ( SnO 2 ) thin films on the Pyrex glass and the microelectromechanical system (MEMS) substrates. The electrode-spacing for the “Nano-Macro” integrated sensor-device is maintained at 1 cm while that for the “Nano-Micro” integrated sensor-device is reduced to 10 and 20 μ m . These sensor-devices with different electrode-spacing are characterized using glancing-angle X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), and high-resolution transmission electron microscope (HRTEM); and subsequently utilized for sensing 900 ppm hydrogen ( H 2 ) at room temperature under the dynamic test-condition. The “Nano-Macro” and “Nano-Micro” integrated sensor-devices exhibit maximum room temperature H 2 sensitivity of 10 3 and > 10 4 with the response time of 3 h and 250–350 s (for the room temperature H 2 sensitivity of 10 2 ), respectively. Moreover, the “Nano-Micro” integrated sensor-device with the smaller electrode-spacing ( 10 μ m ) shows better response kinetics relative to that of the sensor-device with the larger electrode-spacing ( 20 μ m ) . The observed sensor-behavior has been explained based on the effect of electrode-spacing on the kinetics of the H 2 sensing mechanism.