[3dem] carbon rods for evaporation

Bowman, Valorie D vdb at purdue.edu
Thu Mar 7 08:20:47 PST 2013


Dear Kelly,
It sounds like you're not making good contact somewhere in the electrical
system.  I've had this problem with my Emitech when the contact pin wires
got old and frayed (inside the plastic coating).  When current was applied
nothing would happen until a certain level of resistance was met, and then
ZAP!  A big burst would get thru and either blow the tip on the rod or just
blast my grids black.  Replacing the wires fixed the problem.  I've also
seen it when other contacts were not secure.

Check all of your connections, or it may be that thinner rods just don't
clamp tightly enough to make good contact.

Good luck,

Valorie
 


> From: Kelly Dryden <kdryden at virginia.edu>
> Reply-To: <kdryden at virginia.edu>
> Date: Fri, 1 Mar 2013 14:22:21 -0500
> To: <3dem at ncmir.ucsd.edu>
> Subject: [3dem] carbon rods for evaporation
> 
> Hi all,
> 
> Since Edwards no longer makes them, we have a Ladd carbon evaporator.
> However, we are having trouble getting the carbon to vaporize.  The rods
> a slightly thinner than we used previously with an Edwards, and vacuum
> reaches about 2E-6.  The problem is that I can only get a very thin
> layer of carbon after 12-15 times of increasing the current nearly to
> the maximum.  I can't leave it on for too long each time because either
> the rod will blow, or the apparatus gets so hot the plastic film is
> damaged.  All the carbon rods we have tried (the originals from Ladd,
> and from Ted Pella and EMS) appear to be graphite.  I've been unable to
> determine if this has always been true, or if it is creating the problem.
> 
> Any suggestions for helping us get fine-grained carbon coating for our
> grids will be welcome.
> 
> Thanks,
> Kelly
> 
> 
> *********************************************************
> Kelly A. Dryden, Ph.D.
> Assistant Professor of Research
> 
> Dept. of Molecular Physiology & Biological Physics
> School of Medicine, University of Virginia
> Snyder Bldg., Rm. 232
> 480 Ray C. Hunt Dr.
> Charlottesville, VA  22908-0886
> 
> office: (434)982-0525  fax: (434)243-8271
> email: kdryden at virginia.edu
> _______________________________________________
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