Reaction Yields Flat Hydrogen-Coated Surfaces

A simple reaction functionalizes the (100) crystal face of silicon—the surface most commonly employed in the electronics industry—with hydrogen atoms, producing a nearly atomically flat surface (J. Phys. Chem. C, DOI: 10.1021/jp306477x). Melissa A. Hines and colleagues at Cornell University doused Si(100) surfaces in a solution of ammonium fluoride, which they discovered produces uniform functionalization. Although Si(100) surfaces are routinely coated with insulating oxides to fabricate electronic devices, researchers would like to coat the surfaces with organic monolayers in order to make electronic-organic hybrid devices for chemical or biological applications. So far, this has proved difficult, because dense collections of dangling bonds on the Si(100) surface sterically hinder functionalization reactions. The researchers discovered that the steric hindrance can be overcome by the previously unrecognized high reactivity of select pairs of sparsely distributed silicon bonds. The reactivity is intense enough to drive the Si-NH₄F reaction across the surface. The group confirmed the surface functionalization with microscopy, spectroscopy, and simulation studies. The team notes that the H-functionalized surface can then be further functionalized with hydrocarbons.