N-heterocyclic carbenes aminate silicon surfaces

A synthetic approach based on N-heterocyclic carbenes provides a way to covalently link amines and aminals in close proximity to silicon surfaces. The technique could be useful for modulating the electronic properties of silicon chips used in the semiconductor industry.Jeremiah A. Johnson of Massachusetts Institute of Technology and coworkers developed the strategy in which they functionalize silicon by inserting the persistent carbene into Si–H surface bonds (J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.6b04962). Silicon chips could already be aminated in other ways. But the carbene-insertion technique is the first to attach amine groups only one carbon away from the surface, rather than through a typically long spacer group. A one-carbon separation positions nitrogen close enough to the silicon surface to modify how readily electrons can escape, potentially easing customization for specific microelectronics applications. In addition, the well-controlled reactivity of carbenes reduces problematic side-reactions, and the technique derivatizes surfaces with better site-selectivity than some existing amine-insertion techniques. Johnson says his group plans to investigate the performance of these novel carbene-derived monolayers on silicon in solar cells and to explore substrates beyond silicon.