[3dem] glow discharge vs plasma cleaning

Mike Strauss mikestrauss13 at crystal.harvard.edu
Tue Sep 20 11:46:51 PDT 2016


Hi Sergej,

Just a reminder, because I'm sure you are aware, but there are other
factors besides the vacuum that affect the results of the glow discharger
(or plasma cleaner in your case).  These include: distance between
electrodes, voltage applied across electrodes,  shape of electrodes, nature
of carrier (the thing your grids are on), type of residual gas in chamber.

I have always assumed that the name of the instrument depends on its
intended use.  So a glow discharger becomes a plasma cleaner when you leave
it on too long and burn off all the carbon.

mike

On Tue, Sep 20, 2016 at 7:03 PM, Sergej Masich <Sergej.Masich at ki.se> wrote:

> Dear List, dear Benoît,
>
> I have some different experience that can be wrong though. A colleague and
> a good friend of mine from Albuquerque successfully used his plasma cleaner
> to glow-discharge carbon films. I decided to copy his settings in our Lab
> and ordered the same model. However, that model could not be sold to
> European customers due to some regulations. I purchased more expensive
> model from the same supplier. It did not work! As the result of “glow
> discharge”, I got empty grids, no traces of carbon. To make a long story
> short, we installed a needle valve and a gauge to control the vacuum
> degree. We got hydrophilic carbon at poorer vacuum and no carbon at better
> vacuum. Since then, I used the plasma cleaner for many years to prepare
> hydrophilic carbon surface.
>
> In my opinion, this also makes sense. The ions in plasma have longer free
> path at higher vacuum. As the result, they have higher energy that can
> result in more efficient removal of the “dirt” from the surface.
>
> I never read any confirmation of my “theory” that can be completely wrong
> but I hope it will contribute to the discussion.
>
> Sincerely,
> Sergej Masich
>
> =============================
> Dr. Sergej Masich
> Dept. of Cell and Molecular Biology
> Karolinska Institutet
> Box 285
> 171 77 Stockholm, Sweden
> tel: (+)46 - 8 - 524 873 61
> mobile: (+)46 - 736 - 833 693
> e-mail: Sergej.Masich at ki.se
>
> On 20 Sep 2016, at 18:33, <benoit.zuber at ana.unibe.ch> <
> benoit.zuber at ana.unibe.ch> wrote:
>
> Hi David,
>
> This could be right. However I doubt it. Within 20 to 30 minutes we can
> completely disintegrate the carbon of quantifoil grids with the glow
> discharge machine set so that it glows strongly without sparkling.
>
> Cheers
> Ben
>
> ________________________________________
> Von: Morgan, David Gene [dagmorga at indiana.edu]
> Gesendet: Dienstag, 20. September 2016 18:12
> An: Zuber, Benoît (ANA); 3dem at ncmir.ucsd.edu
> Betreff: Re: glow discharge vs plasma cleaning
>
> Ben,
>
>
>    Maybe someone else on the list can shed some light on this, but I don't
> know whether the strength of the plasma created in an EM "glow discharge
> device" is comparable to that of what is called a "plasma cleaner."  I
> suspect not, but could be wrong.
>
>
>    That said, over zealous use of a plasma cleaner can remove _all_ the
> carbon from an EM grid (I have done this with a lacy carbon grid), so
> having too much power can be a bad thing...
>
>
> --
>            David Gene Morgan
>        Electron Microscopy Center
>             047D Simon Hall
>             IU Bloomington
>          812 856 1457 (office)
>          812 856 3221 (3200)
>      http://iubemcenter.indiana.edu
> ________________________________
> From: benoit.zuber at ana.unibe.ch <benoit.zuber at ana.unibe.ch>
> Sent: Tuesday, September 20, 2016 12:06 PM
> To: Morgan, David Gene; 3dem at ncmir.ucsd.edu
> Subject: Re: glow discharge vs plasma cleaning
>
> Hi David and Luiza,
>
> Many thanks for the explanations. OK this « makes sense ». But it is a
> shame that people use two different words for the same thing (good job from
> the marketing team though ! ). It would be much better to use only one term
> and then give specific gaz conditions. So many people are convinced that
> glow discharge and plasma cleaning are two different things and that you
> need two different machines.
> We have a so-called glow discharge machine from defunct Balzers. It still
> functions perfectly well, it looks like what people describe as a glow
> discharge machine : a glass cylinder with two metal plates below and on
> top, and it has an needle-valve inlet. We typically let the inlet in
> contact with the air and let a tiny bit of air flow in to get a constant
> pressure in the chamber and thereby have a reproducible procedure. We can
> quite precisely control the pressure that we want inside. However if we
> want to use whatever gas mixture instead of good old nitrogen and oxygen,
> we can just buy and connect the relevant gas bottle(s). No need to purchase
> a new machine.
> If I listened to what so many people told me, I would have long bought
> another machine, which would probably have been a waste of money and lab
> space. I think people should be more aware of this before spending their
> (tax payer ?) money.
>
> Cheers
> Benoît
>
>
> De : "Morgan, David Gene" <dagmorga at indiana.edu>
> Date : mardi, 20 septembre 2016 17:51
> À : Benoit Zuber <benoit.zuber at ana.unibe.ch>
> Objet : Re: glow discharge vs plasma cleaning
>
>
> Ben,
>
>
>
>    They are technically the same thing _except_ that in common EM usage,
> "glow discharge" is done using ambient gases (i.e., you just pull a modest
> vacuum and create a plasma) while "plasma cleaning" is done using a
> specific mix of gases (Ar, O and with the Gatan device H) instead of
> ambient gases (i.e., you flush the chamber with specific gases, then pull
> the vacuum and create the plasma).
>
>
>
>    With more O in the plasma, the cleaning tends to be stronger (burns
> more material in the sample) and the Ar/O mix prevents side reactions that
> can be caused by the abundant N in the atmosphere.
>
>
> --
>            David Gene Morgan
>        Electron Microscopy Center
>             047D Simon Hall
>             IU Bloomington
>          812 856 1457 (office)
>          812 856 3221 (3200)
>      http://iubemcenter.indiana.edu
> ________________________________
> From: 3dem <3dem-bounces at ncmir.ucsd.edu> on behalf of
> benoit.zuber at ana.unibe.ch <benoit.zuber at ana.unibe.ch>
> Sent: Tuesday, September 20, 2016 11:28 AM
> To: 3dem at ncmir.ucsd.edu
> Subject: [3dem] glow discharge vs plasma cleaning
>
> Dear colleagues,
>
> I often hear people saying: „Did you treat your grid with glow discharge
> or with plasma cleaner?” Or : ”It is absolutely essential for application
> XY to pretreat the grid with a plasma cleaner and not by glow discharge!”.
>
> Can anyone explain what the difference between glow discharge and a plasma
> cleaning is?
>
> According to Wikipedia, this is the same thing (https://en.wikipedia.org/
> wiki/Glow_discharge). The page starts with this sentence:
> “A glow discharge is a plasma<https://en.wikipedia.
> org/wiki/Plasma_(physics)> formed by the passage of electric current<
> https://en.wikipedia.org/wiki/Electric_current> through a low-pressure
> gas”
>
> I look forward to an interesting debate.
> Ben
>
> Prof. Benoît Zuber
> Institute of Anatomy
> University of Bern
> Baltzerstrasse 2
> Postfach 922
> 3000 Bern 9
> Switzerland
> Tel. +41 31 631 84 40
> benoit.zuber at ana.unibe.ch
> http://www.ana.unibe.ch/~exmo/
>
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