[Fwd: Re: Follow up...]

Dick Crane rcrane at snf.stanford.edu
Tue Apr 5 13:39:38 PDT 2005


I have two concerns about the request to evaporate WO3.  I have not 
evaporated this material, but while it sounds like it is mildly tricky 
given the outgassing and subliming qualities, I suspect it would 
evaporate reasonably well. The first concern is that when evaporating 
metal oxides, an oxygen partial pressure is typically needed. The 
Innotec is not set up for this. The second concern is that the film 
stress would cause flaking of the shields and make a mess for other 
users. This is unacceptable. Tom Carver will no longer sputter this 
material in his vac chambers because of the resulting mess.

Try Goddard and Asc.? Scientific Coatings?


Mary Tang wrote:

> Hi all --
> This is more information from Jim Stapleton (Jim Swartz' student) 
> about his request to evaporate tungsten oxide.  It looks a little 
> tricky.  This is something that he would rather have SNF do, since he 
> has no microfab experience and doesn't anticipate making more than a 
> few of these.  So, I've two questions.  First, should this receive 
> SpecMat approval?  Second, should SNF support this?
> Mary
> ------------------------------------------------------------------------
> Subject:
> RE: Follow up...
> From:
> "Jim Stapleton" <drofnats at stanford.edu>
> Date:
> Fri, 1 Apr 2005 17:23:58 -0800
> To:
> "'Mary Tang'" <mtang at snf.stanford.edu>
> To:
> "'Mary Tang'" <mtang at snf.stanford.edu>
>Hi Mary,
>Thanks for taking care of the special materials request for me.  I'm
>attaching the paper I showed you, which has the protocol.
>Also, here's a paragraph from an email the author of the paper sent me
>when I asked him for more information:
>"WO3 is tricky to deposit by e-beam because it sublimes.  Metals and
>other oxides are generally easier because they melt first, and from the
>liquid phase it's much easier to control the evaporation rate.
>Nevertheless, I used e-beam (very carefully) and my sensors worked
>great.  You're just going to need some practice to get good at it.
>Start the evaporation slowly and ramp slowly.  Use a wide sweep (~ 1-2
>cm^2) - don't focus on a small spot like you would with a metal.  If
>they'd prefer that you not use e-beam, then magnetron sputtering would
>be my next choice."
>Here's a link to a MSDS for tungsten oxide:
>If you like I can send you links and pdf's for other papers that make
>these films.  The protocols aren't any more descriptive, but maybe the
>committee will see that people are indeed making these things.
>Thanks again,

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