Characterization Of SnO 2 Nanoparticles Deposited Via Layer-by-Layer Self Assembly And Investigation Of Their Sensing Pr
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Characterization Of SnO2 Nanoparticles Deposited Via Layer-by-Layer Self Assembly And Investigation Of Their Sensing Properties 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 A technique of Layer-by-Layer (LbL) self-assembly is used to deposit SnO2 nanoparticles on Quartz Crystal Microbalance (QCM) resonators, and on glass substrates which the authors believe has not been previously reported. Characterization of self-assembled SnO2 layers has been performed using QCM, Scanning Electron Microscopy (SEM), and Zeta Potential analysis. We have successfully deposited SnO2 nanoparticles on QCM resonator using self-assembly technique. LbL self-assembly is a method of organization of ultra-thin films by interlayer electrostatic attraction. The thickness and mass of the self-assembled layers can be characterized by the frequency shift obtained using the QCM and empirical equations relating change in frequency with mass and thickness of deposited layers. The deposition of SnO2 nanolayers exhibited a linear reproducibility and the process of self-assembly was independent of the residence time of QCM resonator in the SnO2 nanoparticle colloidal solution. High resolution SEM analysis reveals that the SnO2 nanoparticle layers are uniformly deposited across the entire substrate. Electrical characterization was performed on SnO2 nanoparticle layers self-assembled on glass substrates which were patterned for two point (current-voltage) IV characteristic measurements. Two classes of samples were used. One sample was self-assembled glass substrate patterned with electrical contacts and calcined (baked at 350°C for one hour) to eliminate interlayered polyions and the other sample was not calcined. Results revealed that the calcined samples demonstrated linear ohmic behavior but the uncalcined showed some spurious points which we believe are due to the polyion layers. Characterization of the self-assembled SnO2 nanoparticles is being carried out with the intention of fabricating a high-selectivity µ-gas sensor. A test chamber has been fabricated and results of resistance behavior of the sensor with variation in temperature have been presented. The sensor can find applications in high selectivity sensing of chemical, industrial, domestic, and hazardous environments. After further research and development, this µ-gas sensors could be made generic to sense a variety of gases and employed for integrated on-chip product analysis in multiple chemical microsystem applications. INRODUCTION Metal oxides like Fe2O3, TiO2, MoO3, WO3, In2O3, and SnO2 have been employed by material technologists for sensing various gaseous species like NO2, O3, NH3, and CO [1],[2],[3].
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SnO2 has been the most extensively used sensor-element in semiconductor gas sensors for sensing carbon monoxide, oxides of nitrogen, hydrogen sulfide, freon and many others. Several refinements have taken eff
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