I prefer a silane with low boiling point as I am going to deposit it in the vapor phase (chemical vapor deposition).
I have tried TMS (Chlorotrimethylsilane) using CVD on Si wafer and I got water contact angle of ~55 which is not suitable for my purpose. I need something less hydrophobic (30-40 degree).
Your answers will be much appreciated.
You might think about applying the silane using less harsh conditions.
straightforward vapor phase deposition works very well and do not influence the chemical structure of the silane.
Article Silane Deposition via Gas-Phase Evaporation and High-Resolut...
Humidity, acid or base are necessary for the reaction.
Article Analysis of silanes and of siloxanes formation by Raman spectroscopy
You can find additional experiments with siloxane layers in our other publications.
Why do you need something with an apparent CA in-between 30-40 deg?
(You might also think about influencing the liquid phase?)
What about CA hysteresis (advancing, receding)?
We measured for mono(3-aminoproply) siloxane downhill CA in the range of 55deg and uphill angles in the range of 40 deg on the downhill side (tables in the supporting information).
Article Statistical contact angle analyses: 'Slow moving' drops on i...
Unfortunately, freshly RCA cleaned wafers are not time(humidity/oxygen) stable but the CA is exactly in the desired range.
Article Detailed statistical contact angle analyses; “slow moving” d...
Hello Michael,
Thanks for your reply on both of my questions. I need this range of contact angles for a sensor application. I have tried Trichloro(3,3,3-trifluoropropyl)-silane (3FS) and TMS (Chlorotrimethylsilane), they produced water CA of 70 and 55, respectively. I need something around 30-40 as a complementary coating for my application. APTES is exactly what I want in terms of contact angle but its high boiling point is a problem. I was not sure that applying vacuum in a desiccator would be sufficient to vaporize APTES (since APTES boiling point is fairly high ~220 C).
How important is using Nitrogen gas? Can I skip it? Applying Nitrogen gas will make things more complicated since I have to deal with a new set up.
I have also come up with Methyltrichlorosilane. Theoretically, if I am correct, it should make a less hydrophobic surface compared to (trimethylchlorosilane) TMS but I could not find any values of contact angle for it in the literature so I am not sure how much different its contact angle will be.
Thanks for your time Michael Schmitt
We usually use dry nitrogen to separate the layer formation from the reaction leading to very thin layers.
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