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Electron Microprobe Lab, University of Minnesota

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Why did you go and apply the drop of methanol? You might have left well enough alone. <G>

My experience with carbon or gold coatings is that they are not very robust. We have some clients that like to sputter layers of gold for other purposes than for conductivity inside the microscope. Often it is for a reflective surface. Then they find that the layer wipes off somewhat easily. I can usually use a dry cotton swab to wipe the layer off of a glass slide with a little rubbing. 

The coatings will do fine for conductivity under the beam, but they do not adhere particularly well. I would recommend not putting them to the test. 

Probably there is someone out there with more experience that can tell us what might be expected under the best conditions, or what might be done to make the coatings adhere better. 

Warren Straszheim
Iowa State University and Ames Laboratory

-----Original Message-----
From: JEOL-Focused Probe Users List [mailto:[log in to unmask]] On Behalf Of Brian Joy
Sent: Friday, September 02, 2011 10:45 AM
To: [log in to unmask]
Subject: [PROBE-USERS] problem with carbon coating

JEOL Probe Users Listserver

Moderator: Ellery Frahm, [log in to unmask],
Electron Microprobe Lab, University of Minnesota

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Hi everyone,

I'd like to ask a question regarding a problem I've been having while
carbon coating.  I am using a Denton Desk V coater with turbomolecular
pump and rods consisting of compressed powdered graphite (from Ted Pella,
1/8" diameter, grade 1 "spec-pure").  I can obtain coats of appropriate
thickness (i.e., between 1st-order red and 2nd-order blue) that look very
good.  However, after coating polished brass or glass, when I place a drop
of methanol on the surface of the coat, the coat disintegrates within a
matter of seconds.  Has anybody seen this sort of behavior before?  I
assume that it must be due to presence of contamination under the coat. 
I've checked the inlet to the roughing pump, and I see no oil residue
after several months of use.  Any suggestions?

Brian


-- 
Brian Joy
Electron Microprobe and ESEM Lab
Queen's Facility for Isotope Research
Department of Geological Sciences and Geological Engineering
Queen's University
36 Union Street
Kingston, Ontario K7L 3N6

cell phone: 530-220-0434
lab phone: 613-533-2595
fax: 613-533-6592

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