Advanced preparation methods for TEM specimens
Q&A
Advanced preparation methods
for TEM specimens
Q&A
We are so glad that many of you came to the "Advanced preparation methods for TEM specimens" webinar on the 5th of October. Hopefully you got a lot of useful information from the presentation.
Here you can find all the questions raised during the Q&A session.
Q: What is the difference between the single-sided cooled and the
single-sided clamped sample holders
for UniMill?
A: In the cooled holder, a special glue (Leit-C) is used to mount the sample. This is needed for proper heat conduction between the cooled holder and the sample. To use this glue some skills are needed and you will find it a bit inconvenient if you do not need it. In the clamped holder two spring-loaded clams are holding the sample in position. It is very easy and safe to mount/unmount the sample and the potential contamination by glue is also excluded from the process.
Q: Could you explain why we need different holders for FIB cut samples and Ar milled samples in the GentleMill?
A: The FIB holder is optimized for minimal redeposition, that is why there is minimal material close to the sample. The other holder for the Ar milled samples allows more alignment if you have a hole not exactly in the middle of the disc. Also, sample mounting is a bit different for the two types, and we believe these holders make it safer to handle the different types (FIB/Ar mill). But you can use both holders for all kinds of samples, you will get good enough results.
Q: What will be the temperature of a sample during ion milling?
A: It depends on many factors. In normal cases, a Si sample should remain under 250°C. If you have a material that is not conducting heat very well, e.g. glass thin parts at the end of the preparation process will heat up much more. You can melt glass this way (~600°C) The power of the ion beam is also an important factor if you have a heat-sensitive material surely you will not try a 16 keV Ar beam, instead, 6-8 kV is recommended if the cooled holder does not solve the problem alone.
Q: What is the delivery time of these ion mills?
A: You will get the exact delivery time when you place the order, normally it is 8-10 weeks. If a shorter delivery time is important, please inform us how the project moves forward, and let us know the desired configuration before you please the PO.
Q: What is the price of the UniMill system?
A: It depends on the configuration, like cooling unit, automated software, different sample holders, etc., please contact our local partner, Mr. Sanjay Vaidya from Samar Instruments for an up-to-date quotation.
Q: Can you use the low-energy gun at 2000 V to thin the samples?
A: Yes, you can, but it will take longer compared to the case where you use the HEG. The upper range of the LEG is used if you have a sample which is almost good and little thinning is needed. But I am sure you will have other ideas to use it when you get started with the ion mills.
Q: Can you prepare non-conductive material with Ar ion milling?
A: Yes, you can, in our experience, this is not a problem in contrast to FIB where a charging sample may need extra attention. A piece of Al2O3 mills fine, of course, it is a hard material and you will need the 16 kV setting to keep the milling times short. Still, you may have difficulties with a charging sample in the transmission electron microscope. A very thin coating of a-C can help if it does not disturb the experiment.
Q: What is the usual energy range for Ar cleaning?
A: It depends on the sample but in most cases, 500 V can be used as a first step and 300 V as a second step. In special cases, 200 V or less is also used.
Q: You mentioned a lot of other tools like diamond saw, grinding machine etc. Can I buy these separately or are they sold with the ion mills?
A: Yes, you can buy them separately.
Q: Are there any tricks to increase the electron transparent area of an Ar ion milled sample?
A: You already have a very large area compared to FIB (50 -100 times larger). You can still make it larger but that will require very careful processing matched to the specific material. If you need help with such a problem please let us know the details and we will do our best to help. You solve it.
Q: So ideally do you recommend having both UniMill and Gentlemill in a TEM prep lab?
A: It depends on which TEM sample preparation approach is more b eneficial for the laboratory’s samples. For FIB sample cleaning GentleMill, for the whole TEM sample preparation, UniMill is the best choice. In case both FIB and conventional TEM sample preparation are necessary, then yes, a laboratory equipped with UniMill and GentleMill is ideal.
Q: What is the minimum temperature for the cooling stage?
A: Depending on the pre-cooling time, we can reach lower and lower temperatures. Generally, the stage temperature is less than -100°C in 30-40 minutes. Of course, by applying longer pre-cooling times, lower stage temperatures can be reached.
Q: Is there any provision for bulk sample milling?
A: UniMill is designed for milling about 50-70 um thick disks (3 mm diameter). This can still be considered as bulk material. If you mean larger pieces by bulk material, the mechanical preparation is needed before UniMill can be used. For this process, we offer a complete range of tools and materials (most of them were shown in the presentation) which will help you to complete the job reliably and efficiently.