I am trying to image a membrane made from PDMS using environmental SEM. The pore size of this sample is 50um, but ultimately we may be going down to 10um. I have the membrane bonded to a glass slide, but I can prepare it differently if there are better suggestions.
Do I have to sputter coat the sample before imaging? I have seen PDMS membranes imaged by ESEM in literature, and I don't believe they coat it.
Does anyone have any tips?
Thanks,
T^2
Remember PDMS is an insulator. When electron beam falls on the materials, it charges the surface and one can't record the picture, so either charge shouldn't build or has to go off the surface. In SEM you have to use very low KV to observe PDMS surface without coatings. You may also try using a grid of copper or carbon tape running from the sample surface to the bottom of the holder. If you see your image is shrinking or moving, it means that you are using too much KV. No need to coat in ESEM as it would help a lot.
As you are using the environmental mode, you can get away without coating, but I don't see the reason why you shouldn't. The coating particles are less than nanometer, so they don't affect your image. I recommend carbon coating if you want to have EDS analysis as well.
Remember PDMS is an insulator. When electron beam falls on the materials, it charges the surface and one can't record the picture, so either charge shouldn't build or has to go off the surface. In SEM you have to use very low KV to observe PDMS surface without coatings. You may also try using a grid of copper or carbon tape running from the sample surface to the bottom of the holder. If you see your image is shrinking or moving, it means that you are using too much KV. No need to coat in ESEM as it would help a lot.
As someone who images soft materials, I come across this issue often. I find it easier to coat samples when the dimensions of the feature of interest are in the micron scale. You could coat the sample with a conductive layer (preferably Carbon), a few nms in thickness (and ground the top surface). This will make your life a lot easier. Additionally this wont adversely affect any of your pore size calculations.
You can try to observe your specimen in ESEM mode first. Quality of ESEM pictures depends very much on SEM itself (FE SEM could be very helpful) and on specimen (yes, resolution is very much specimen-dependant). If you have good FE SEM low voltage pictures (without coating) could be better than ESEM pictures (but again it is specimen dependent). And, of course, you can coat your specimens. I believe you do not need to perform EDS analysis, and for high resolution pictures metal coating (such as Au-Pd) is much better choice than carbon coating. Do not overcoat (a few nm coating is sufficient). Rule of thumb: for middle of the line SEMs high magnification pictures of metal-coated specimens are much better than ESEM or low voltage pictures.
With AFM - there is large adhesive interaction - liquid environment is better. However, for 50 um pore size - only part will be visible. For diameter of 10 um - pores are nicely visible under AFM.
- Badges
- Science method