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Chemomechanical Production of Submicron Edge Width, Functionalized, ∼20 μm Features on Silicon

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journal contribution
posted on 20.11.2002, 00:00 by Yit-Yian Lua, Travis L. Niederhauser, Brent A. Wacaser, Ian A. Mowat, Adam T. Woolley, Robert C. Davis, Harvey A. Fishman, Matthew R. Linford
We recently reported that monolayers on silicon are formed, and silicon surfaces concomitantly patterned, when native oxide-coated silicon is scribed with a diamond-tipped instrument in the presence of reactive liquids. Notably, monolayers were prepared (and are prepared in this work) in an open laboratory with reagents that are not degassed. However, while this method is facile, the features originally produced using 2−3 N of force on a diamond tip are irregular, broad (∼100 μm), and deep (∼5 μm). Reducing the force to 0.08 N using an improved tip holder yields narrower features (∼10 μm), but the best features made with a diamond tip using the lighter force still remain quite deep (∼0.1 μm) and rough. Here we show that substantially sharper and shallower features are produced by (a) wetting hydrogen-terminated silicon with a reactive compound and (b) scribing it with a 1/32 in. tungsten carbide ball with a low force (∼0.08 N). It is remarkable that (i) the depth of these features is only 10−20 Å and (ii) their edge widths are sharp (submicron resolution). The resulting features are invisible to the naked eye but are observable by atomic force microscopy, scanning electron microscopy, and time-of-flight secondary ion mass spectrometry. Both Si(100) and Si(111) were successfully modified. Miniature hydrophobic corrals made with this technique were loaded with solutes, for example, colloidal carbon, semiconductor nanocrystals, and DNA, from aqueous solutions with a simple dip. Under appropriate conditions colloidal carbon selectively deposits onto functionalized lines but not in between them.