Hello, I am currently working on preparing samples for TEM observations. These samples are sintered Barium Titanate with various dopants in the form of ceramic capacitors. The method I am using to prepare the samples is the tripod polishing wedge method. What I have read so far is preparation methods for a Silicon sample, and for this type of sample the color changes once the sample is electron transparent when viewed under the Visible light microscope (VLM).
Dose any one know how I can determine if my samples are electron transparent, using the VLM? what i have seen is that there is a point where my samples are transparent to visible light but not sure if this also makes them transparent to electrons.
Thanks in advance for your help
Dear Victor,
electron interaction with matter especially the electron propagation through matter is a though task to deal with and to understand.
However a lot of work has been done in the past. So please refer to the ESTAR/Nist calculator. Here you can enter your material parameter and please look at the CSDA range (continouos slow down approximation). This value will be displayed in g/cm². Please divide the CSDA values by the density of your sample, so you will get a measure of the penetration depth of the electron in your sample (please pay attention to the units and the orders of magitude). I think for distances of far smaller than this value your sample will be 'transparent' for electrons of the specified energy.
A 'little' draw back: at my Computer the ESTAR caluclator does not work properly: sorry; so I cannot provide the data for your BaTiO3. Please try by youself.
For elements however the calculator works. As an example I have attached the CSDA range values for Ba. So you will get a rough estimation of which order of magnitude of distances your will have to deal with.
Additional remark: please read the ESTAR decriptions, so you will get a little impression on the subject.
http://physics.nist.gov/PhysRefData/Star/Text/ESTAR.html
I suggest you try to employ polarisator. The thickness fringes will give you a good idea about the thickness. the sample in attachment was wedge-polished and additionally thinned by Ar+ ion mill. Not sure if inset is from same sample (I was sloppy while taking images), but the white region below last blue-pink-yellow ring is thin enough for the electrons (for TEM).
Transparent to visible light means the sample is getting thin, but not necessarily thin enough. You will likely need to polish until you get the sample as thin as possible with no hole, then ion beam mill just until there is a hole. Sometimes the edges of the hole will be sufficiently electron transparaent.
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