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

Abstract

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.

Selective bonding of pyrazine to silicon(100)-2×1 surfaces: The role of nitrogen atoms

“…45 Thus, our result strongly indicates the adsorption of pyrazine involving direct Si-N bond formation. A single N 1s peak centered at 399.0 eV is resolved for chemisorbed pyrazine ͓Fig.…”

“…27,45,47 The C 1s core level of the four carbon atoms of pyrazine also displays a down shift of 0.8 eV upon chemisorption, attributable to the higher electron density at carbon atoms due to the loss of electron withdrawing of nitrogen atom in chemisorbed pyrazine molecule. The downshift disproves the formation of a dative bond ͑Fig.…”

Tetra-σ attachment of allyl cyanide onSi(111)−7×7

“…19 The photoemission at 283.8 eV is ascribed to -C 2 H(Si)-C 1 H 2 (Si), well in line with dibonded ethylene on Si͑100͒. 27,28 The actual assignments and relative intensities of fitted spectra for chemisorbed and physisorbed molecules are listed in Table II. The significant down shifts of C 4 and N atoms of the cyano group and C 1 and C 2 atoms of the vinyl group strongly suggests that both C 1 vC 2 and C 4 wN functionalities are involved into the direct reaction with the Si surface, which is consistent with the evidences shown in our HREELS experiments ͑see Table III͒.…”

“…26 The photoemission feature at 285.6 and 284.5 eV are associated with C 1 H 2 vC 2 H-and -C 3 H 2 -, respectively, in good agreement with the C 1s BEs determined for the C atoms with sp 2 and sp 3 hybridizations in alkenes. 27 The spectrum of chemisorbed molecules with a narrower FWHM was also fitted into three peaks at 285.1, 284.5, and 283.8 eV with an area ratio of ϳ1:1:2 ͓Fig. 5͑c͔͒.…”

Scanning Tunneling Microscopy of Organic Molecules and Monolayers on Silicon and Germanium (001) Surfaces

“…Our recent work has focused on investigating the interaction of these compounds with the Silicon (001) surface as a potential means of forming well-defined interfaces between silicon and organic materials. [20][21][22][23][24][25][26][27][28][29] While there are many possible ways in which substituents could be attached to the surfaces of silicon, there are several aspects of cycloaddition chemistry that are particularly interesting. First, we note that since cycloaddition reactions do not involve cleavage of any C-H or C-C bonds, adsorption of organic substituents to the Si(001) surface can take place at room temperature with the formation of strong covalent bonds.…”