Silicon Monomer Formation and Surface Patterning of Si(001)-2 x 1 Following Tetraethoxysilane Dissociative Adsorption at Room Temperature

The adsorption of tetraethoxysilane (TEOS, Si[OC2H5](4)) on the Si(001)-2 x 1 surface at 300 K is studied through a joint experimental and theoretical approach, combining scanning tunneling microscopy (STM) and synchrotron radiation X-ray photoelectron spectroscopy (XPS) with first-principles simulations within the density functional theory (DFT). XPS shows that all Si-O bonds within the TEOS molecules are broken upon adsorption, releasing one Si atom per dissociated molecule, while the ethoxy (-OC2H5) groups form new Si-O bonds with surface Si dimers. A comparison between experimental STM images and DFT adsorption configurations shows that the four ethoxy groups bind to two second-neighbor silicon dimers within the same row, while the released silicon atom is captured as a monomer on an adjacent silicon dimer row. Additionally, the surface displays alternate ethoxy- and Si adatom-covered rows as TEOS coverage increases. This patterning, which spontaneously forms upon TEOS adsorption, can be used as a template for the nanofabrication of one-dimensional self-organized structures on Si(001)-2 x 1.