Volume 90 Issue 36 | p. 59 | Concentrates
Issue Date: September 3, 2012

Reaction Yields Flat Hydrogen-Coated Surfaces

Chemical treatment could spur development of silicon-based electronic-organic hybrid devices
Department: Science & Technology
News Channels: Materials SCENE
Keywords: Silicon, surfaces, functionalization, electronics
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An STM image of a hydrogen-functionalized Si(100) surface. Depth increases from yellow to purple.
Credit: J. Phys. Chem. C
A STM image shows a hatching pattern of yellow bars on a purple background.
 
An STM image of a hydrogen-functionalized Si(100) surface. Depth increases from yellow to purple.
Credit: J. Phys. Chem. C

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.

A Monte Carlo simulation shows the propagation of a hydrogen functionalization reaction across an initially ideal flat (left) and vicinal Si(100) surfaces (depth increases from yellow to purple).
Credit: Melissa Hines
 
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ISSN 0009-2347
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