Tin Dioxide Opals and Inverted Opals: Near-Ideal Microstructures for Gas Sensors
✍ Scribed by R. W. J. Scott; S. M. Yang; G. Chabanis; N. Coombs; D. E. Williams; G. A. Ozin
- Publisher
- John Wiley and Sons
- Year
- 2001
- Tongue
- English
- Weight
- 321 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0935-9648
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✦ Synopsis
tip imprints. The findings stimulate a variety of mechanistic questions which concern stoichiometry issues in the AgCl and deposition kinetics. A more systematic study on the kinetic and thermodynamic parameters that determine these issues as well as the morphology of the silver deposits is in progress.
In summary, it could be shown that the cathodic deposition of silver on AgCl occurs preferentially in mechanically prestructured tracks. This effect can be used to write miniaturized and complex metal structures on solid electrolytes. A next step is the attempt to achieve directed structuring on the nanoscale.
Experimental
AgCl single crystals were polished (alumina with a particle size of 0.03 lm) and etched in Na 2 S 2 O 3 solution (13.4 g/L). A silver paste electrode (counter electrode) was painted on the back of the crystals. Using a micromanipulator (PH150, Karl Suss, Dresden), a tungsten microelectrode with tip radius 1 lm was slightly pressed onto the AgCl surface and then moved along the surface to scratch structures (e.g., letters or lines) into the relatively soft AgCl crystal (Fig. 1a,b). This pre-structuring process was controlled under the optical microscope. The same set-up was used to deposit silver on the pre-structured AgCl solid electrolyte (Fig. 1c): The micro-tip was positioned in the scratch and a voltage of ±0.5 V to ±10 V (vs. counter electrode) was applied. The formation process of the silver on the surface was observed under the optical microscope in situ. After switching off the voltage a more detailed analysis of the silver deposits was performed by SEM, EDX analysis, and AFM.