Anyone have experience with a Leica coater? Thread or Rods?

[Dominique]

Hello,

We're looking to buy a second coater shortly to back up our ageing JEOL unit. The Leica EM ACE600 seems versatile enough, but I'm not able to get enough information from users located around here, or the local dealer, on the carbon rods. The dealer seems to be pushing the carbon thread model, as that's what they know.

But the threads can coat max 10 nm with one set, and apparently double that if we double the thread.

A few questions... When you double the threads, do you truly get about 20 nm of coat? Or is the coater less efficient when you double?
If you have rods, does the coat work well with this system? Is the coat comparable to a JEOL coater, or on the lesser end of the spectrum like our old Denton (poor vac)?

We have last minute funding so I'm looking for any feedback ASAP   

Thanks!

[Peter Horvath]

Hi Dominique,

We have the Leica EM ACE600 here with a double sputter head, one is for carbon and the other for metal coating. We do double threads and we get truly 20 nm of coat. It is easy to use and it is very efficient. I have no experience with carbon rods using this instrument.

Cheers,
Peter

[Dominique]

Hi Dominique,

We have the Leica EM ACE600 here with a double sputter head, one is for carbon and the other for metal coating. We do double threads and we get truly 20 nm of coat. It is easy to use and it is very efficient. I have no experience with carbon rods using this instrument.

Cheers,
Peter

Thanks very much for your feedback!

[Probeman]

I'm sure everyone knows this, but I would simply add that the absolute thickness of a carbon coat is less important than its reproducibility. That is, even 10-15 nm of carbon is often sufficient to provide sample conduction, but the critical question is: are both the standard and unknown coatings the same mass thickness?

This is particularly critical in two instances. First, when measuring very low energy emission lines, e.g., N ka or O ka, where they are significantly absorbed by carbon, and second, when measuring emission lines with a low over voltage, e.g., Fe Ka at say 15 keV or less, and a small difference in carbon coat thickness can significantly reduce the "landing energy", and hence the generated intensity (see Fe K emission over voltage curve).

The main reason we usually apply a 20 nm thickness is, I suspect, that historically we use the color change on polished brass to determine the carbon coat thickness:

https://probesoftware.com/smf/index.php?topic=921.msg7063#msg7063

The color change at around 20 nm (red to blue) is quite obvious (violet) and hence usually provides the best reproducibility while looking at the color from the reflected light of the arc.  Of course today we have quartz thickness monitors, but I'm chagrined to say that the thickness monitor on our venerable Edwards 306A carbon evaporator has long since failed, so we continue to determine thickness on polished brass.

http://www.geology.wisc.edu/~johnf/g777/AmMin/Kerrick_C-coat.pdf

Speaking of the color violet, does everyone know why the color spectrum named by Newton (ROYGBIV) has 7 colors?  Because really, what exactly is the difference between violet and indigo?  Here's a discussion of one possibility why we have seven colors:

https://www.dailybreak.com/break/cabinet-of-curiosities-why-indigo-is-in-the-rainbow

This is also worth a read:

https://en.wikipedia.org/wiki/Indigo

[DavidAdams]

I'm just going to leave this right here

https://en.wikipedia.org/wiki/Color_blindness#Red%E2%80%93green_color_blindness

[Probeman]

I'm just going to leave this right here

https://en.wikipedia.org/wiki/Color_blindness#Red%E2%80%93green_color_blindness

Hi Dave,
It's a worthy point. Did you see the extended discussion on this topic (color palettes) here:

https://probesoftware.com/smf/index.php?topic=1003.msg6583#msg6583

[Anette von der Handt]

Hi,

I have the Leica AC600 as well and use the carbon thread. You should reliably get 20nm with the double thread. I coat with 12 nm usually and we use the double thread method to get two coatings out of it. If I use the single thread I am not always getting my 12 nm, so double thread it is and it seems to be more efficient rather than less

I am very happy with the quality of the coating from the thread but it adds to the running costs as the thread is quite pricey. Nevertheless, since we got this coater we never had a problem with coatings while we often ran into problems with the old one, carbon-rod based one. I don't know if it is the combination with the thread or just the coater though.

[sem-geologist]

My sincere advice is stay away from the rods, leave it to be bought by clueless people. We have both - (rod - on Quorum, Thread on Leica), rod is most stupid thing ever created and should had never make to market.

[sem-geologist]

Anette,

At the beginning we were also getting wasteful with Leica coater, thus I am going to give an advice. I experience that it is possible to use double thread for 3 or even 5 times to coat up to 20 nA. To get to such economy the vacuum is very important. The problem is that Leica's coater have very stupid vacuum interface - it is bar without any numbers and it shows the "good" vacuum prematurely. The bar being full (green) does not mean that in real the optimal vacuum for the coating was reached. I see very huge improvement in coating quality and economy of thread if I let it pump at least 20 minutes (if pump is cold) or 10 minutes (if pump is warm) for getting really good vacuum, and only then launch the coating program. Even with single thread I am getting 2 times x 20nm, and with double It can last twice more (once got 5 x 20nm).

[Doug_Meier]

Rather than waiting additional time after the "good" condition has been reached, it is also possible to go into the settings and adjust the pressure threshold for the "good" coating condition to a more suitable value.  This way, samples that outgas at different rates can be accommodated without worrying whether a XX minute wait in the "good" zone is sufficient for a given sample.

[Dominique]

The problem is that Leica's coater have very stupid vacuum interface - it is bar without any numbers and it shows the "good" vacuum prematurely. The bar being full (green) does not mean that in real the optimal vacuum for the coating was reached. I see very huge improvement in coating quality and economy of thread if I let it pump at least 20 minutes (if pump is cold) or 10 minutes (if pump is warm) for getting really good vacuum, and only then launch the coating program. Even with single thread I am getting 2 times x 20nm, and with double It can last twice more (once got 5 x 20nm).

Thank you very much for the tip! We also have the same problem starting up HV mode on our old SEM; the vacuum metre turns green prematurely, and it's best to wait a few more minutes.

[Rom]

Hi,

I have the Leica AC600 as well and use the carbon thread. You should reliably get 20nm with the double thread. I coat with 12 nm usually and we use the double thread method to get two coatings out of it. If I use the single thread I am not always getting my 12 nm, so double thread it is and it seems to be more efficient rather than less

I am very happy with the quality of the coating from the thread but it adds to the running costs as the thread is quite pricey. Nevertheless, since we got this coater we never had a problem with coatings while we often ran into problems with the old one, carbon-rod based one. I don't know if it is the combination with the thread or just the coater though.

Anette, could you clarify several points:
1. What differences of current (amps) if you use 1, 2 or more threads? The chosen current for 1 thread should be multiplied to number of threads?
2. Do you use continuous or impulse regime, what difference in your opinion?
3. What optimal level of vacuum for good coating - do you have some numbers or just indicator position))?
Thank you!