Nano-Design of Oxide Particles and Electrode Structure for High Sensitivity NO 2 Sensor Using WO 3 Thick Film
- PDF / 2,802,656 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 10 Downloads / 180 Views
A1.4.1
Nano-Design of Oxide Particles and Electrode Structure for High Sensitivity NO2 Sensor Using WO3 Thick Film Jun Tamaki Department of Applied Chemistry, Faculty of Science and Engineering, Ritsumeikan University, Kusatsu-shi, Shiga 525-8577, Japan ABSTRACT Novel sensor design for high sensitivity gas sensors has been proposed for the detection of dilute NO2 using WO3 film. First, concerning nano-design of oxide particles, the disk-shaped WO3 particles (300 nm in diameter, 20 nm in thickness) were deposited on Au comb-type microelectrode (line width : 5 µm, distance between lines : 5 µm) to be WO3 thick film sensor. This sensor showed the excellent sensing properties to dilute NO2 at optimized thickness. Second, the nano-gap electrode with various gap-sizes (110-1500 nm) was fabricated by means of MEMS techniques in order to investigate the effect of microelectrode. When the gap size was decreased less than 800 nm, the sensitivity to dilute NO2 increased with decreasing gap size. This was understood from the facts that the contribution of interface resistance between particle and electrode to total sensor resistance was increased and that the sensitivity at electrode-grain interface was much larger than that at grain boundary. It was found that the designs of not only nano-particles but also nano-electrode were important for the fabrication of high sensitivity gas sensor. INTRODUCTION WO3 is well known to be an excellent sensing material for the detection of NOx [1, 2]. Recently, the conductivity-type NO2 sensors using WO3 were improved in their sensitivity by adopting thin film structure [3-5], by doping foreign oxide [6-12], and by using novel preparation method [13-16]. Namely, these WO3 based sensors could detect dilute NO2 less than 1 ppm. In my laboratory, the high sensitivity NO2 sensors have been investigated mainly by focusing the particle design and electrode structure. In the first part of this paper, the disk-shaped WO3 particles were deposited on Au comb-type microelectrode (line width : 5 µm, distance between lines : 5 µm) [17-19]. The WO3 thick film sensor equipped with Au comb-type microelectrode showed extremely high sensitivity to dilute NO2. This sensor could detect 0.02 ppm NO2 with high sensitivity. Second, the nano-gap electrode was fabricated by means of MEMS techniques in order to elucidate the effect of microelectrode [20]. The sensitivity to dilute NO2 increased with decreasing gap size in the range less than 800 nm. In this paper, novel sensor design for high sensitivity NO2 sensor is proposed, especially in particle and electrode design. EXPERIMENTAL Both the Au comb-type microelectrode and the nano-gap electrode were fabricated on Si substrate by means of MEMS techniques. In the former, the 300 pairs of Au line (width : 5 µm)
A1.4.2
were fabricated with distance between lines of 5 µm in the area of 2 mm x 3 mm by photolithography. On the other hand, the nano-gap electrode was fabricated in two steps. First, the Au line with width of 11-16 µm and thickness of 0.3 µm was deposited
Data Loading...
