Figures from "Cycloaddition Chemistry of 1,3-Dienes on the Silicon (001) Surface: The Competition Between [4+2] and [2+2] Reactions", by J.S. Hovis and R.J. Hamers, Journal of Physical Chemistry B, vol. 102 (35), 6873-6879 (1998).

© 1998 American Chemical Society

Note: All the figures shown here have been published and copyrighted. If you use or reproduce any of these figures in any way, you must indicate the original source of the image. For electronic or paper publication, you must receive written permission from Robert Hamers and the American Chemical Society.

Figure 1

STM images showing the Si(001) surface after it was exposed to 0.1 Langmuir of 2,3-dimethyl-1,3-butadiene at room temperature and a schematic illustration showing the position of the adsorbates with respect to the underlying dimers. The images were acquired with a tunneling current of 200 pA and a sample bias of -2.4V

Figure 2

FTIR spectra of the Si(001) surface after the adsorption of 2,3-dimethyl-1,3-butadiene. The top spectrum was taken after 0.1 Langmuir exposure at room temperature; a two-domain sample and unpolarized light were used. The bottom spectrum shows an ice of DMBD created by exposing the surface to 100 Langmuir at 100 K.

Figure 3

Schematic illustration of the interaction of 2,3-dimethyl-1,3-butadiene with the Si(001) surface.
a) [2+2] interaction of one 2,3-dimethyl-1,3-butadiene C=C bond with a Si=Si dimer
b) [4+2] interaction of both 2,3-dimethyl-1,3-butadiene C=C bonds with a Si=Si dimer

Figure 4

FTIR spectra of the Si(001) surface after the adsorption of 1,3-cyclohexadiene and room temperature. A two-domain sample and unpolarized light were used for the top spectrum, the exposure was 0.1 Langmuir. A single-domain sample and s-polarized light, with the dimer orientation indicated in the figure, we used for the bottom two spectra, the exposure was 5 Langmuir.

Figure 5

STM images showing the Si(001) surface after it was exposed to 0.1 Langmuir 1,3-cyclohexadiene at room temperature and a schematic illustration showing the position of the adsorbates with respect to the underlying dimers. The images were acquired with a tunneling current of 150 pA and a sample bias of -2.2V.

Figure 6

FTIR spectra of the 1,3-cyclohexadiene saturated Si(001) surface heated to the temperature indicated; the spectra were all acquired at room temperature. The initial surface was prepared by exposing a single-domain Si(001) surface to 5 Langmuir at room temperature. S-polarized light was used for all the spectra with the direction of the electric field being perpendicular to the dimer axis.

Figure 7

7. FTIR spectra of the Si(001) surface after the adsorption of 1,3-cyclohexadiene. The top spectrum shows an ice of CHD created by exposing the surface to 10 Langmuir at 100K. The bottom two spectra were taken after exposing the surface to 5 Langmuir at 300K and 1 Langmuir at 120K respectively. Single-domain samples and s-polarized light were used for the bottom spectra; the direction of the electric field was perpendicular to the dimer axis.

Figure 8

Schematic illustration of the interaction of 1,3-cyclohexadiene with the Si(001) surface.
a) [2+2] interaction of one 1,3-cyclohexadiene C=C bond with a Si=Si dimer
b) [4+2] interaction of both 1,3-cyclohexadiene C=C bonds with a Si=Si dimer


Figure 9

Schematic illustration of spatial distribution of p bonding and p * antibonding orbitals for Si=Si in (a) bent and (b) planar configurations. For each geometry is also shown a schematic depiction of the filled p bonding orbital of an alkene interacting with the empty p * antibonding orbital of the Si=Si dimer. Note that interaction is unobstructed for the bend Si=Si dimer configuration at top, but is sterically hindered for the planar configuration at bottom.

Last updated Dec. 19, 1998