Introduction:

Purpose: To remove organic material from substrate

Location: General purpose fumehood

Chemicals: sulfuric acid, hydrogen peroxide and DI water

Supplies Needed: 2 glass or Pyrex dishes, volumetric cylinders or beakers, hotplate, tweezers (acid resistant tweezers or PEEK/TEFLON tweezers), texwipe, nitrogen gun, chemical warning form and PPE

Setup Procedures:

1. Find an available fumehood that is not used for any process and make sure that the area is free of other chemicals.
2. Fill out the chemical warning form (located at the fumehood) with proper warning information (chemicals, contact information, process time and hazards).
3. Notify research users using the same hood that you are going to prepare Piranha solution.
4. Using bottle carries, bring a bottle of sulfuric acid and a bottle of hydrogen peroxide to the fumehood.
5. Place the glass/Pyrex dish onto the hotplate and put on PPE.
6. Measure a precise amount of sulfuric acid with the volumetric cylinder/beaker, slowly pour the acid into the dish, do NOT exceed 1/3 of the volume of the dish.
7. Use the 3:1 (H₂SO₄: H₂O₂) ratio to determine the amount of H₂O₂, measure with a volumetric beaker or cylinder.
8. Slowly pour the hydrogen peroxide into the piranha solution dish. The reaction begins immediately and produces large amounts of heat.
9. Set the hotplate temperature to 150ºC, let the solution come to needed temperature (120 ºC) in about 10-15 min.
10. Prepare a clean glass/Pyrex container while you wait. Fill out another chemical warning form. Triple rinse a glass or Pyrex dish with DI water, then fill the dish with DI water. Set the dish off to the side.

Number of substrates: 1

Process Procedures:

1. Using metal or peek tweezers, carefully place your sample into the piranha solution.
2. Return the chemical bottles to the chemical storage cabinet.
3. After 10-20 minutes, remove your sample from the piranha solution and place it into the container of DI water.
4. . Turn off the hotplate and leave the piranha solution dish on the hotplate, allow it to cool.
5. Rinse your sample thoroughly with running DI water (30 seconds). Rinse your tweezers and the spots where tweezers touch the substrate
6. Place your sample on a texwipe and blow dry with the nitrogen gun. Use a sweeping motion while working from one side of the sample to opposite side (1 min).
7. Once the piranha solution is cooled below 40 ºC (approximately 2-3 hours), while wearing PPE gear, carefully pour it down the sink with plenty of running city water.
8. Rinse the piranha solution container.
9. Remove chemical warning form and clean up any spills.

Time:  approximately 45 minutes + cool down time

Comments:

1. Do not use plastic tweezers or tweezers with a plastic or rubber coating as the piranha will react with organic materials.
2. Be sure to rinse your tweezers immediately after transferring your sample in and out of solution.

Verification:

1. Particles level: can be observed under microscope with dark field, or measured with Surfscan
2. Hydrophobicity: can be measured with contact angle measurement tool