Cycloaddition Chemistry on Silicon(001) Surfaces: The Adsorption of Azo-tert-butane

The adsorption of azo- tert -butane on the Si(001) surface at 300 K has been investigated using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, scanning tunneling microscopy (STM), and ab initio computational chemistry methods. Although some cleavage of C−H bonds that prevents the formation of a completely ordered layer occurs at room temperature, adsorption onto a 130 K surface occurs molecularly with no bond cleavage. All of the experimental evidence shows that adsorption occurs through the interaction of the N N azo bond with a single Si Si dimer bond, in a manner similar to a [2 + 2] cycloaddition reaction. These results show that the use of [2 + 2] cycloaddition reactions to link organic substituents to the Si(001) surface is not limited to alkenes but can be extended to link compounds which have other types of unsaturated bonds to the Si(001) surface.