CHEMICAL MODIFICATION OF THE SI(111)-7X7 SURFACE WITH MULTI-FUNCTIONAL ORGANIC MOLECULES

Abstract

Functionalization of the semiconductor surfaces with organic molecules in a highly selective fashion has been an important subject to explore the feasible way to fabricate ordered molecular patterns or uniform organic layers. The hybrid organic/semiconductor interfaces show potential applications in molecular electronics, biosensors and nanotechnology. However, the coexistence of multiple reaction pathways of multi-functional organic molecules binding on the semiconductor surfaces makes the selective attachment of organic molecules extreme difficult and challenging. The aim of this study is to understand the drive force for the selective attachment of multi-function organic molecules, including benzaldehyde, acetyl cyanide, propargylamine and allyl chloride on the Si(111)-7×7 surface by using high resolution electron energy loss spectroscopy, scanning tunneling microscopy and density functional theory calculation. A highly selective reaction of benzaldehyde is discovered via the C=O group binding on the Si(111)-7×7 surface, forming a [2+2]-like cycloadduct. Acetyl cyanide is found to interact with Si(111)-7×7 through a [4+2]-like cycloaddition. The two unsaturated hydrocarbons (propargylamine and allyl chloride) with different substitutions show high reactivity towards dissociative reactions. The temperature dependence of the site selectivity is investigated for the binding of allyl chloride with the formation of molecular patterns.