Author Topic: clean up ftm crystal  (Read 1600 times)

Ben Buse

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clean up ftm crystal
« on: September 25, 2018, 09:38:06 am »
Hi All,

Any ideas on how to clean up a FTM quartz crystal.

Thanks

Ben

Mike Matthews

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Re: clean up ftm crystal
« Reply #1 on: September 25, 2018, 11:21:55 am »
Hi Ben,

I’d be surprised if you could use mechanical method and either shatter it or just ruine it’s acoustic response. That leaves chemical. I’m pretty sure the crystal is just pure qtz so at least it’s fairly robust to most corrosives. I’d start with the simpler acids (does HCl dissolve Ag?) and work your way up to the mixtures (e.g. aqua regia) until you find something that works. I presume there’s a reason not simply replacing it?

Probeman

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Re: clean up ftm crystal
« Reply #2 on: September 25, 2018, 12:03:17 pm »
What about an oxygen plasma cleaner?  That should do a nice job though it will be slow.
john
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jrminter

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Re: clean up ftm crystal
« Reply #3 on: September 25, 2018, 03:09:07 pm »
Check out your TEM lab to see if they have a Gatan Solarus cleaer. These can use H2 and O2 which ashes at a lower temperature. My lab had one and it was great for these tasks.

Gseward

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Re: clean up ftm crystal
« Reply #4 on: October 17, 2018, 10:09:43 am »
I have a Emitech K950X (EMS 950X in the US) with their FTM. I use the FTM in a passive mode, i.e not controlling the deposition. Perhaps it is not the worlds most sophisticated FTM either, but...
I remove the crystal from the holder and carefully scrape the accumulated debris off the crystal with razor blade. I have been doing this for at least 10 years.
I can't comment on the accuracy of my FTM, (other than by occasionally coating a piece of brass) but my reproducibility hasn't changed much in 10 years - given some care and a reproducible setup (rod diameter and length, number of deposition pulses, pulse length, spring tension, position of rods, etc) my FTM returns 20nm +/- 1nm 90% of the time; larger deviation is usually associated with sloppy rod preparation and inaccurate rod positioning.   

Gareth


Probeman

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Re: clean up ftm crystal
« Reply #5 on: October 17, 2018, 12:30:45 pm »
Our FTM device stopped working a long time ago on our Edwards 306A evaporator, so we've always relied on observing the color transition from red to blue (violet) on polished brass. Which occurs right around 20 nm thickness:

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

I can't say that we are as accurate as +/- 1 nm, but probably +/- 2 to 4 nm.   Given that, if we really need to have the carbon coats exactly the same thickness on both the standards and the unknowns, we usually repolish the standard mount and coat it at the same time as the unknown.

Keeps the standard mounts nice and clean!   :)
« Last Edit: October 18, 2018, 09:32:36 am by Probeman »
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