Formation of ordered, anisotropic organic monolayers on the Si(001) surface

It is shown that the Si=Si dimers of the reconstructed Si(001) surface can react with the pi bonds of unsaturated organic molecules to produce well-defined organic films with novel physical properties. Scanning tunneling microscopy (STM) studies show that the resulting layers are ordered both translationally and rotationally, with the Si=Si dimers acting as a template for extending the translational and rotational order from the silicon substrate to the organic film. STM images and infrared spectroscopy experiments show that by using vicinal Si(001) surface having primarily double-height steps, the rotational order of the molecules can be preserved over macroscopic length scales, leading to measurable anisotropy in optical properties. It is proposed that this chemistry may provide a general method for formation of controlled organic films on Si(001) surfaces.