Piranha Cleaning

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Necessary Materials

1. >95% Sulfuric Acid Solution (H2SO4)

2. ~30% Hydrogen Peroxide Solution (H2O2)

3. Glass containers

4. Ceramic boats

5. Holder tweezers for ceramic boats

6. Access to deionized water (DI) water

Procedure

Important:

  • Make sure to wear acid resistant lab coat, gloves and face shield while doing piranha cleaning.
  • Piranha solution is a strong oxidizing agent, it removes most organic matter.
  • It hydroxilates most surfaces (adds -OH group) making them highly hydrophilic.
  • Rinse all empty containers 3 times with DI water before disposing.


* The steps outlined below are for piranha cleaning of glass slides necessary for one run of Lesker Thin Film Deposition, during which ~24 glass slides can be sputtered on a 6 inch wafer. However, given procedure can be applied for any samples that need to be piranha cleaned. Note: np - Au samples have different procedure for piranha cleaning - modifications are outlined in bold in the procedure below.


1. Load two ceramic boats with glass slides (22 mm X 22 mm), ~12 glass slides per boat.


2. Mix 400 ml H2SO4 + 150 ml H2O2 in a glass container to make 3 : 1 piranha solution.


3. Let the piranha solution cool for 1 minute. For np - Au samples piranha cleaning, let the solution cool for 10 minutes.


4. Immerse the ceramic boats loaded with glass slides in the piranha solution using metal tweezers designed for ceramic boat use.


5. Keep the slides in piranha solution for 7 minutes. For np - Au samples piranha cleaning, keep each sample in the solution for 20 seconds only.


6. Transfer the boats to a glass container with DI water. Keep it there for at least 1 minute.


7. Wash the slides under the DI water stream, but be cautious not to break them, because they are very fragile.


8. If the samples are to be used the same day, dry clean them with N2 gas and store in the parafilmed Petri dish. If for some reason they are not to be used on the same day, leave the slides in the DI water and dry on the day they are to be used, although it is recommended to use piranha cleaned slides on the same day of cleaning. Keep np - Au samples in the parafilmed container with DI water at all times until they are to be used.


9. Aspirate used piranha solution and clean all the glassware and working surfaces excessively using DI water.