AFM of pnc-Si and alumina coated membranes
I’ve been working with the AFM recently and have had some success getting images on supported pnc-Si films. Yesterday, I imaged three samples from sc 698: one untreated pnc-Si film and two films coated with aluminum oxide (1.5 nm and 5 nm thickness). Here are the scans (500 nm x 500 nm).
The topmost scan is the untreated sample followed by the two alumina coated films. The pore entrances appear conical, but this may be an artifact of the cantilever tip (diameter 10 – 25 nm) falling into a pore. Although from TEM micrographs and Maryna’s cross-sectional SEM work we know that there is probably some kind slope to the pore wall.
TEM micrograph of sc 698
I tried to extract an RMS roughness from the scans above using only the solid film portion, but the sampling area was too small and there was a large amount of variability in the values. I will need to create a custom mask to exclude the pores from the calculation in order to extract a true RMS value.
Qualitatively, we see that the alumina coating appears to slightly roughen the film.
I’m a little skeptical that depositing 1.5nm could create such a large change, while adding another 3.5nm makes a little difference.
Another strange feature is that the pores in the uncoated sample appear to be shallower than in the Al3O3 coated samples. It seems like the tip was not following the surface in the same way and could be artificially smoothing out the fine features.
I think it would be important to figure out if this observation is real, by trying to get a scan of the uncoated sample where the pores look the same as the coated samples. Keep in mind that the surface properties of our bare membrane may be very different than the alumina, so the scanning parameters may need to be adjusted.