I am depositing Al onto PMMA via thermal evaporation. Currently I have already tried to improve the adhesion of the films by two different strategies:
1. Evaporating SiO prior to the Al deposition i.e PMMA+SiOx+Al
2. Introducing/eliminating air plasma etching performed before the evaporation of Al or SiO+Al mixture
I can't achieve proper adhesion of the Al films. The Al films totally delaminate after tape test no matter which combination of the two listed strategies I use. Does anyone have any experience with this kind of thermal evaporations? Any reccomendation about other adhesive layer alternatives beside SiO with high adhesion on PMMA?
please view this link
https://patents.google.com/patent/US20130022756A1/en
Hi Jerson,
I have not specific experience in evaporation, I perfomred mainly sputtering of Al on polymeric substrates and PMMA as well with successful results.
Be careful with plasma, it must be performed at low pressure and gently otherwise it can damage the surface of the polymer.
Furhter, be sure that your substrate does not increase temperature before or during deposition, this is very detrimental for adhesion because it can damage the surface of PMMA as well generate residual stresses during cooling down.
Lacquering should be also a solution as performed to metallize the paper.
good luck,
Best regards,
Simone
What is the Al thickness? If it's < 50 nm I'm surprised it's delaminating. If it's 50-150 nm then you might be able to do a 5-10 nm Ti layer first to help. If it's more like 300-500 nm then you might have to look at lowering film stress by raising/lowering the dep rate or adding substrate heating.
I have tried Al. but not on PMMA, I have tried on Kapton. I observed two things. if the vacuum conditions are poor don't expect a very good quality of Al deposition. We had two evaporators, the one with a very high vacuum (>5*10^-6) order gave a better deposition compared to one at (>5*10^-5). Second, I have improved the surface energy of Kapton by chemical modification. I introduced a highly hydrophilic surface which improved the adhesion. second, the chemical modification introduced a nanoscale surface roughness which improved the adhesion. however, in your case, the air plasma did not improve the condition which is one of the ways to introduce hydrophilic behavior. if that doesn't work, I suggest you find proper "silanes" compatible for your material.
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You can try Plasma surface treatment (vacuum plasma or atmospheric plasma) on the PMMA surface before sputtering Al. However, it is necessary to pay attention to the process of sputtering Al as soon as possible after Plasma treatment.
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