Silicon is a versatile substrate for building of optical and electro-chemical sensors for environmental, chemical and bio-applications. For easier handling during use, the initial surface in the preparation of the sensor as well as the starting surface for the sensing process should be stable in environmental conditions but reactive to specific further processing. Here we address the preparation and characterization of ultrathin passivated/functionalized surfaces for efficient binding of scavenger or specific analyte molecules. The highly sensitive IR ellipsometric analysis in a single reflection geometry of various passivated/functionalized silicon surfaces is presented. Historically the hydrogen passivation is one of the most used ones, but lacks on a long-term surface stability in environmental conditions. Another well-known direct functionalization of the silicon with OH groups for further processing is chemical treatment of oxidized silicon surfaces and further functionalization by silanization. A drawback here is that the oxidized interface can reduce the electrical and sensing performance. We present an alternative path for the preparation of stable hydroxyl/benzyl terminated Si surfaces without the need of a SiO<sub>2</sub> layer.

Ultrathin functionalization of silicon surfaces

ACS Fall 2021

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