Formation of a tetra-sigma-bonded intermediate in acetylethyne binding on Si(100)-2 x 1.
The covalent binding of acetylethyne on Si(100)-2 x 1 has been investigated using high-resolution electron energy loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS). The HREELS spectra of chemisorbed monolayers show the absence of the C=O, C[triple bond]C, and C(sp)-H stretching modes coupled with the appearance of C=C (at 1580 cm(-1)) and C(sp2)-H (at 3067 cm(-1)) stretching modes. This demonstrates that both of the C=O and CC groups of acetylethyne directly participate in binding with silicon surfaces to form C-O and C=C bonds, respectively, which is further confirmed by the XPS studies. A tetra-sigma-binding configuration through two [2 + 2]-like cycloaddition reactions in acetylethyne binding on Si(100) is proposed to account for the experimental observation. The cycloadduct containing a C=C double bond may be employed as an intermediate for further in situ chemical syntheses of multilayer organic thin films or surface functionalization.
Huang
Hai Gou
HG
Department of Chemistry, National University of Singapore, 10 Kent Ridge, Singapore 119260.
Cai
Ying Hui
YH
Huang
Jing Yan
JY
Tang
Hai Hua
HH
Xu
Guo Qin
GQ