Thickness and uniformity of PDMS layers
The last few times the spinned PDMS layers were much more uniform. The first picture below is with 1:100 diluted PDMS layer coated on it and the second one is a clean sample from the same wafer for comparison.
The PDMS layer on the first picture is approximately 60nm thick. The measured thikness produced by the same solution on bare silicon wafer is 57nm (ellipsometer) with uniformity 5% (RSD).
Solution diluted 1:20 gave a layer 231nm thick with unifromity 10% on silicon wafer.
The permeability measurments for thin layers are not very accurate because of the presence of pinholes on the membranes, but polymer layer seems to decrease permeability a lot. I will make few pinhole free premeasured samples to get more accurate data.
Hey Maryna, what was the spin rate and duration used for the production of the PDMS film? (was it 6000 RPM and 150 s ?). Have you looked into what happened if the PDMS was UV ozone bonded to the pnc-Si?
Yes 4000-6000rpm for 150s. I tried ozone treatment before the spinning. Is this what you mean?