Ways of creating micron sized dots on surfaces

Hi!
I am looking for a technique by which i can apply micron/sub-micron sized dots on flat surfaces. Can i sputter fine dots of some metal say
Aluminum on the surface of a substrate? Else, is it possible to etch fine dots over a Al coated substrate by spraying some etchant over it??
If you are aware of any technique, please let me know. Thanks.
---|Rahul|---
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snipped-for-privacy@yahoo.com (Rallyjo) wrote:

Read up on the old fashioned rotogravure color printing processes. You could try using a crossed diffraction grating to lay down a pattern of etch sensitive or etch resistance or ink attractor or ink rejected micro-zones. You will have to do some design calculations for the optical gratings, I suppose. Maybe your rotogravure paper research will turn up tables and the like. Good luck.
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If you are happy with a few microns 10 - 50 to start with and you're not really bothered about the pattern a suggestion is to use a fine wire mesh. Place the mesh on your substrate, evaporate your metal and then take off the mesh. Its basically a stencil, sometimes called evaporation shadow masks....... You can have them custom made, down to 20 micron features or you can try the cheap method and buy electron microscopy grids (a few quid each). These grids go down to 5 microns in size but I'm not sure you'd every get those type of features
Paul
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Consider using a suspension of uniformly sized spheres (typically polystryrene, as I recall). They are commercially available. With the right concentration, surface preparation, etc., you can get them to self-assemble onto a substrate (e.g. microscope slide) as the solution evaporates. In some areas, you'll get a monolayer of hexagonal close packed spheres. Vacuum evaporate metal (e.g. silver) over the spheres and lift off the spheres. You'll be left with an array of dots, well, actually triangles. Annealing can turn the triangles into round dots.
For details, check out this site:
http://www.chem.northwestern.edu/~vanduyne /
See the "Nanosphere Lithography FAQ" link, left-hand column.
It's not very controlled approach, but without any fancy optical or e-beam lithography equipment, you can obtain some areas of arrayed dots of uniform size. It also can be used for reactive ion (plasma) etching of the surface, since the spheres tend to stay in place on the surface and serve as an etch mask for shallow etching of the substrate.
Good luck!
Grant

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