"Front Matter". In: Organosilanes in Radical Chemistry - Index of

Radical Chemistry on Silicon Surfaces 211
well-ordered monolayer with surprisingly high coverage (97 %) [64]. For comparison,
the analogous reaction with 1-octadecene afforded a 55 % coverage.
The dependence of monolayer formation on the wavelength of the irradiation
light (400–350 nm) and the reaction time has been studied in some details [64].
Interestingly, the optimum wavelength for both C
w O and C C additions was
w
found to be about 385 nm, whereas later it was reported that the reaction
efficiency increases monotonically with decreasing wavelength up to 254 nm
(see Figure 8.4). However, the ability to photoinitiate the reaction of unsaturated
compounds with H Si(111) opens the possibility of direct photopattern-
w
ing of organics on the surface. Figure 8.6 shows schematically the lightpromoted
hydrosilylation with 1-alkene in the presence of a mask that can
pattern the surface. The first photolithographic accomplishment to write
>100 mm features, was obtained by exposing to 385 nm light through a structured
mask octadecanal with an H S(111) surface [64]. It was further demon-
w
strated that the unexposed areas remained completely reactive.
mask
Si
Si
H
Si
H
Si
Si
Si
Si
Si
H
Si
H
Si
hν
Si
Si
H
Si
H––Si(111)
Figure 8.6 Schematic representation of light promoted hydrosilylation through masking procedure.
Si
Si
Si
Si
Si
R
Si
Si
R
H
Si
Si
Si
Si
R
Si
Si