Characterization of Self-Assembled SnO 2 Nanoparticles for Fabrication of a High Sensitivity and High Selectivity Micro-
- PDF / 113,657 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 29 Downloads / 162 Views
Characterization of Self-Assembled SnO2 Nanoparticles for Fabrication of a High Sensitivity and High Selectivity Micro-Gas Sensor R.C.Ghan, Y. Lvov, and R.S.Besser Louisiana Tech University Institute for Micromanufacturing 911 Hergot Avenue, P.O.Box 10137, Ruston, LA, 71270. Fax: (240) 255-4028 Email: [email protected] ABSTRACT In order to refine further the material technology for tin-oxide based gas sensing we are exploring the use of precision nanoparticle deposition for the sensing layer. Layers of SnO2 nanoparticles were grown on Quartz Crystal Microbalance (QCM) resonators using the layer-bylayer self-assembly technique. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Electron Diffraction Pattern (EDP) analyses were performed on the selfassembled layers of SnO2 nanoparticles. The results showed that SnO2 nanoparticle films are deposited uniformly across the substrate. The size of the nanoparticles is estimated to be about 35 nm. Electrical characterization was done using standard current-voltage measurement technique, which revealed that SnO2 nanoparticle films exhibit ohmic behavior. Calcination experiments have also been carried out by baking the substrate (with self-assembled nanoparticles) in air at 350°C. Results show that 50%-70% of the polymer layers (which are deposited as precursor layers and also alternately in-between SnO2 nanoparticle monolayers) are eliminated during the process. INTRODUCTION Solid-state gas sensors find applications in automobiles, toxic and domestic environments, the chemical industry, and elsewhere. The gas-sensor market is fast burgeoning and was estimated to be about $0.9 billion at the end of the last decade [1]. Ceramic SnO2 has been used extensively as a sensor element in semiconductor gas-sensors for detecting a range of gases such as carbon monoxide, oxides of nitrogen, hydrogen sulfide, freon and many others [2]. SnO2 is the prime choice for semiconductor sensors because of its bulk-material stability and resistivity characteristics. Sensors with SnO2 as sensing element function on the principle of surface chemical reaction between an analyte gas and the sensing element, which causes a change in the resistance of the element. Thus the sensing characteristics depend on the surface properties of the element [3]. While performing sufficiently for commercial deployment, these sensors displayed a variety of material issues including the degree of crystallinity of SnO2, crystallite size, density of lattice defects, surface area, and surface structure. These issues translated to low or varying selectivity and sensitivity of the SnO2 sensors. Some of the techniques that have been implemented for improving the selectivity include cyclic manipulation of the sensor temperature, doping of the SnO2 with various additives like Pt and noble metals [3], surface modification of the base metal oxide with hydrophobic groups, calcium oxide, zinc oxide and sulfur [4]. The V7.7.1
method of fabrication is also a variant in the process to improve the per
Data Loading...
