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Cleaning and Patterning Indium Tin Oxide-Coated Glass

 

Cleaning Glass Substrates (with or without ITO coating)

  1. Preclean glass slide with acetone using purity wipes (soft lint-free cloth).
  2. Prepare an aqueous solution of 10% NaOH.
  3. Heat proper amount of solution to 55 C (a 250 ml beaker is usually sufficient).
  4. Place slides in NaOH for 3 minutes.
  5. Rinse in deionized water for about I minute, and check that water sheets off slide right away.
  6. Immediately wipe dry with a purity wipe to prevent water spots.

Patterning Indium Tin Oxide Electrodes

Apply tape in user-specftied pattern to an ITO-coated glass slide.

Use yellow VWR labeling tape. It is acid-resistant and sticks to the ITO very well, but not to plain glass. Use one strip over the location of ITO electrode to be left after etching, trimming at ends of slide. Trim the tape to the desired electrode width using an aluminum template. Wipe off the exposed ITO with isopropanol and a purity wipe to remove adhesive residue for best etching.

Etching

  1. Prepare an aqueous solution of 20% HCI and 5% HNO3, plus a few drops of liquid detergent to promote ITO wetting.
  2. Heat proper amount of solution to 55 C (again, a 250 mI beaker is usually sufficient).
  3. Place slides in solution for 2 minutes. Time may vary somewhat.
  4. Rinse in deionized water for 1 minute. Again, check to see that water sheets off slide.
  5. Immediately wipe dry and check resistance of etched glass with an ohmmeter to assure ITO removal. If there is measurable resistance ( <30 MΩ), place slide back in solution for another minute, rinse, dry, and check again. (Depending upon the number of slides being etched, the solution may need to be changed. 20 slides have been etched with the same amount of solution without noticeable loss of etching ability.) It is recommended that the deionized water be changed frequently to prevent acid residue on the slides.
  6. Peel off tape.
  7. Clean slide with isopropanol to remove remaining adhesive residue. Electrode strips should be clearly visible as light violet under glancing reflection, or noticeable as dark stripes against a light background. Check with ohmmeter to assure conductivity.
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