daragh8008
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thin high temperature resistant coatings
Hi,
I've been trying to find a material that I can coat as a form of resist through through pore sizes of about 50-100nm. I'm hoping to deposit 20-50nm
layer but I'm having difficulty coming up with ideas. Bascially the coating should be temperature resistant up to 900-1000C and not reactive with
metal oxides such as MgO and ZnO. What I was thinking was using a very dilute solution of CuSO4 and evaporating onto the surface, followed by heating
to 650C to hopefully form CuO. Does anyone have any ideas on how this might go? Would CuO form a thin film or suitably dense packing to stay stable
(ie. in place ) for a little while longer or would I find the CuO on the roof of the furnace. Any suggestions welcome.
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JohnWW
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Diamond-Like carbon (DLC) coatings are supposed to be the best. They have been discussed in other threads, especially in the Technochemistry section.
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daragh8008
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Indeed they do sound like they would be up to the job, however I'm not sure that I'll be able to aquire the setup for that. Any thoughts on the idea I
suggested?
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watson.fawkes
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| Quote: | Originally posted by daragh8008
I've been trying to find a material that I can coat as a form of resist through through pore sizes of about 50-100nm. I'm hoping to deposit 20-50nm
layer but I'm having difficulty coming up with ideas. |
What is the substrate to be protected and what is the
material trying to resist?
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daragh8008
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THe substrate is Si[111] covered with zinc oxide seed layer( i think the seeds are [002] perpendicular to the substrate). ontop of that is a
porous/textured polystyrene layer. The holes that I want to coat into are through the polystyrene to cover the seed layer. Once selected areas are
coated the pollstyrene is to come off and Carbothermal reduction growth is to be done on the remaining areas aka the areas not coated with the mask.
Thanks
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DrP
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Look up "Geo Polymers" on google. You get some sodium silicate and chuck in a load of mullite - paint it on and let it dry. You then have to cure it
at a few hundered degrees. If you don't cure it it will foam up at high temp and give a ceramic-type char which is highly insulating. Problem is this
char will melt around 850C unless cured off.
\"It\'s a man\'s obligation to stick his boneration in a women\'s separation; this sort of penetration will increase the population of the younger
generation\" - Eric Cartman
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watson.fawkes
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| Quote: | Originally posted by daragh8008
Once selected areas are coated the pollstyrene is to come off and Carbothermal reduction growth is to be done on the remaining areas aka the areas not
coated with the mask. |
Hmm. Your reduction process is going to be reducing your resist, if possible. Is this
a problem? Is it a feature?
Is there a risk that the carbothermal process you're anticipating will form SiC on the substrate? Would SiC formation be a bad thing? Probably yes for
electrical applications and no for mechanical ones, but I don't know the larger context.
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not_important
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I suspect that metal and semimetal alkoxides may be the way to go. Al, Ti, Zr, Si, Mg, Nb, and others, all form alkoxides soluble in organic
solvents, and react with water - liquid or vapour - to form the metal oxide/hydroxide.
They can be modified, silicon and titanium often have amine radicals attached to the metal MCl + HNR2 => M-NR2 + HCl, then reacted with the
alcohol to form the modified alkoxide. Modified alkoxides have been used to form thin films, or as bonding enhancers for other coatings. In some
cases with high amino loading a nitride or oxynitride is formed after firing, rather than an oxide.
Some metal alkoxides form mixed alkoxides with the alkali metals, these can form glasses when hydrolysed and fired. Similarly boron or phosphorus can
be included as glass formers.
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daragh8008
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THanks for the suggestions. IT has given me food for though. I'm not worried about the reduction process. What I do is mix graphite and zinc oxide and
grind them together. Its then heated down stream in a tube furnace in an argon stream at 900C. This grow nicely aligned wires on seeded substrates.
Will give the alkoxides a look over. I'm wondering if the application of alkoxides will dissolve the seed layer. Could be worth a try. THanks for the
ideas though
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daragh8008
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Well it sort of worked in the end, some stayed on the substrate but most coated the furnace. I think some fine tweaking is required. Might change the
sulphate to the hydroxide in situ for a lower temperature decomposition. And see how that gets on.
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