Fwd: SiO2 nanospheres

Mary Tang mtang at stanford.edu
Tue Jan 12 08:06:15 PST 2010

Hi Carter ---

Sorry about that.  To cut down on spam to SpecMat at snf,  mail is accepted 
only from registered addresses -- so I believe it only from your coral 
login at snf or the address you forward to from the SNF computer are 
considered legitimate addresses.  If you email from anywhere else, it 
may be rejected.  You can talk to Maureen about setting up your 
forwarding email appropriately.

As for your SpecMat request, I'm afraid we do not allow silica 
microspheres to be spun up at the headway2 station.  Nanoparticle 
solutions have a tendency to aerosolize and then fly all over the place 
-- and almost permanently stick to surfaces (benchtop, shields, 
cassettes, wafers).  We do allow latex particles at this station because 
these are no worse than resist -- they will come off in sulfuric clean 
or plasma ashing and so are not likely to cause lasting damage to other 
people's work.  However, metal, semiconducting, silica nanoparticles and 
nanotubes in solution can potentially do serious damage to others' work.

If you are templating with silica nanospheres, spin coating will result 
in only limited local self-assembly.  You will need to make sure your 
nanospheres are ionized/charged and diluted in nanopure water.  If you 
need self-assembly over the whole wafer, you might consider talking with 
Chingmei Hsu in Yi Cui's lab, as she uses a Langmuir-Blodgett trough to 
do whole wafers.  Alternatively, you might consider spin-coating latex 
spheres instead --- depending on your depth of etch, the selectivity of 
resist to silicon is typically around 4:1 and can yield nicely vertical 
pillars.  Usha Raghuram and Mingliang Zhang have done some 
characterization, I believe.

Lastly, we did have another spin coater located outside the lab for 
spinning solutions of nanoparticles (like silica) other than latex.  
However, this died just before shutdown and we haven't yet tried to 
repair or replace it.  We will, but it may be some weeks before it is 
available again.


Carter Lin wrote:
> Hi Mary,
> I was trying to send the following email to specMat but was
> unsuccessful. Can you please tell me who will take care of my material
> request?
> Thank you
> Carter
> ---------- Forwarded message ----------
> From: Carter Lin <carterlin at stanford.edu>
> Date: Mon, Jan 11, 2010 at 4:30 PM
> Subject: SiO2 nanospheres
> To: SpecMat at snf.stanford.edu
> Hi, SNF specMat staff, I'd like to bring the following chemicals into
> our cleanroom please.
> Name: Carter Lin
> Coral login: carterlin
> Phone: 617-259-7988
> Email: carterlin at stanford.edu
> PI: Bianxiao Cui, Chemistry department
> Chemicals:
> * SiO2 silica nanospheres 250nm diameter in water
> * SiO2 silica nanospheres 400nm diameter in water
> * SiO2 silica nanospheres 550nm diameter in water
> Vendor:
> 3590 Route 9, Suite 107
> Cold Spring, NY 10516
> Phone: 1-845-208-7027
> Reason for request:
> To use the nanosphere as etch mask for Si wafers
> Process Flow:
> The nanosphere solution will be spincoated onto Si wafers in the
> headway station, then the Si substrate will be etched in lampoly. The
> nanosphere mask is then removed by HF.
> Amount and form
> All three type of nanospheres are in liquid form, each is 10ml.
> Storage:
> I will be storing my materials in SNF.
> Disposal:
> The nanosphere mask will be removed by HF.
> Thank you
> Carter
> --
> Ziliang Lin / Carter Lin
> Applied Physics, Stanford University

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at stanford.edu

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