I have polymer composite film samples. The thickness of my sample is around 1.5 mm. While calculating piezo-coefficient via AFM, there is no response. Can anyone let me know the optimum sample thickness required and what else can be the reason for no response?
Thank you
Is your film fully oriented or is the polymer assembled randomly? At least in crystalline materials misorientations can kill your piezoelectricity, see e.g.
Article Abnormal Grain Growth in AlScN Thin Films Induced by Complex...
Jürgen Weippert The fillers in my polymer matrix are randomly dispersed so the film is not oriented. And my polymer is semi-crystalline. When studying the P-E loop, I am getting some response. But in AFM I am unable to get any response, so I fathomed, that might be due to sample thickness or instrumental issue.
Dear Akanksha Adaval , if your sample is actually 1.5 mm thick it could be the problem, one and a half millimeters is a lot for AFM.
Hope it helps.
Fully agree with Manuel, AFM is used to measure thin film thickness of coatings. Normally it is within a range of a few angstrom to nanometer, not millimetre.
Manuel Gómez and Xuhua Wang Thank you for your replies. Appreciate it.
I am not having much experience in AFM, however, we had the same problem by using a glass slide (1mm) and it was too thick for the tip of the AFM. Currently, a thiner slide (~70-100 micrometers) is working.
Ofir Menashe Okay. Now I have reduced the thickness of my film to around 60-80 micrometers. Do we need to place it on glass slide during AFM Analysis?
It might work, if you will fix it on a slide cover glass.
Please note that I used a slide cover glass as a carrier for the culture (heated fix culture). The slide cover glass is about 50 micrometers and the sample itself is estimated around 20-50 micrometers, overall 70-100 micrometer thick.
dear Akanska,
The typical issue in PFM is to properly polarize the substrate. Glass slide would not be the best substrate for the polymer as it is not conductive so Any metallic substrate would be better.
On the other hand, thickness is another issue as the effective electric field between the metallic substrate and the conductive tip will decrease with the thickness of the polymer thickness. Normally in AFM by default you cannot apply more than 10 Volts of bias (unless you have a voltage amplifier) so the smaller the thickness of the polymer the easier will be to induce a measurable response.
Just to give you a hint: typical LiNbO test samples are glued with silver paint to a metalic disc (typically used for AFMs) on the bottom side and they have a thickness of around 500 microns. With that you can measure piezoelectric response in AFM (i.e. images) with few volts, (theoretical d33 is somewhere around 10 pm/V). For a polymer sample like you mention I would recommend a few microns thickness.
Hope this helps
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