[3dem] glow discharge vs plasma cleaning

[Morgan, David Gene]

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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