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Team:Cambridge/Protocols/Substrate Preparation for Flow Coating and Spin Coating
From 2011.igem.org
Substrate preparation
Methods used to prepare and clean the silicon substrates we used for flow coating and spin coating.
Theory
Cut the silicon pieces to size and wash them to remove surface debris, thus improving the properties of the films.
Various methods were employed, the best films seemed to come from high pressure washing with liquid CO2 (performed by Dr Matthew Hawkeye)
Substrates can be either washed in acetone whilst being sonicated and baked in an O2 plasma oven or Washed with high pressure, liquid CO2. The acetone dissolved contaminants whilst sonication vibrates the crystals to make loosely attached debris become free, whilst the O2 plasma oven introduces an excess of reactive oxygen species to burn off any organic contaminants.
CO2 pressure washing physically displaces debris and leaving a smooth surface for spin and flow coating as it rapidly evaporates.
Practice
Silicon substrates are cleaved using a diamond scribe to introduce a fine nick in the surface of the single silicon crystal. Then upward pressure at the nick and downward pressure at the edges of the crystal an be used to gently and precisely fracture the silicon in two.
Acetone bath and sonication is achieved by placing the substrates in a rack and placing in a beaker filled with enough acetone to cover them. This is covered with foil and placed in a sonicator for 10 minutes. Following this the O2 plasma oven can be used to burn off contaminants, we used 10 minutes in this oven to make sure our samples were clean.
CO2 pressure washing was not performed by us, and is as simple as pointing the pressure washer and pulling the trigger. This is performed in a fumehood and uses a strong vacuum to stabilize the sample during washing.
Safety
Acetone was kept in squirt bottles in the fume hood, as was the beaker containing the substrates during sonication. Foil was used to keep debris out and acetone in the beaker. The O2 plasma oven was a self contained unit, operated and loaded by Dr Matthew Hawkeye, as was the CO2 pressure washer.
