STM and HREELS investigation of gas phase silanization on hydroxylated Si(100)

The gas phase anhydrous reaction of glycidoxypropyldimethylethoxysilane (GPDMES) with a model hydroxylated surface has been investigated using high-resolution electron energy loss spectroscopy (HREELS) and scanning tunneling microscopy (STM). Water dissociation on the clean reconstructed (2 × 1)-Si(100) surface was used to create an atomically flat surface with ~ 0.5 ML of hydroxyl groups. Exposure of this surface to GPDMES at room temperature under vacuum was found to lead to formation of covalent Si-O-Si bonds although high exposures (6 × 108 L) were required for saturation. STM images at the early stages of reaction indicate that the reaction occurs randomly on the surface with no apparent clustering. The STM images together with semi-empirical (AM1) calculations provide evidence for hydrogen bonding interactions between the oxygen atoms in the molecule and surface hydroxyl groups at low coverage.