Subject: Re: stuff on the stage
From: James Conway <>
Date: Thu, 11 Aug 2005 12:54:56 -0700

Hello Lindsay:

This could be a possibility. When I open the system I will take a closer 
look at the material.  Indium smears really easily and I should be able 
to determine if it is metallic and soft.  There was so much of this 
material I would be surprised if it could have been transferred so 
easily just by clipping a sample down.  But then if they are mounting 
with In onto the sample holder that's another issue which they should 
have gained approval before doing.  The material seemed pretty hard on 
my quick inspection yesterday and left significant raised relief over 
the aluminum surface under the clips.  Now small samples cannot be 
clipped flat to the holder and wafers will not mount level to the 
surface.  This will affect quality of writes for everyone.

Thank you for your inputs!

James Conway

Lindsay Shannon Moore wrote:

>Perhaps you have solved the mystery of the "conductive epoxy" on the stage,
>but in case you have not, I thought that I would mention that it is pretty
>common practice to put indium or gallium on the back of MBE grown
>heterostructure wafers to secure them in the MBE machine.  A pretty large
>amount of this soft metal stays on the back of the wafer even after
>removing it from the MBE chamber.  It is possible that the material that
>you found was In or Ga that transfered off the back of someone's wafer. 
>The melting point of Ga is 60C, so this is less likely than In.  In any
>case, there are etches that can selectively remove In, so I thought that I
>would mention this to you as a possible way to save the sample holder in
>case you haven't thought of it yet.  I have no idea who was responsible,
>and, in fact, don't even recognize most of the users who are listed in the
>Raith history over the last week.
>Good luck!