functionalized surfaces on porous silica by atomic layer ... - Aaltodoc

Figure 19. Aminopropylsiloxane network on one nm 2 of silica. VI
4.3 Growth of organic multilayered polyimide structures on amino-<strong>functionalized</strong> silica
A number of organic precursors that can be vaporized at low temperatures without
decomposition can be used to deposit organic multilayered structures onto porous or planar
<strong>surfaces</strong> by ALD. As an example of the deposition of these structures on porous silica, the
formation of polyimide structures on aminosilylated silica is illustrated below (Figure 20).
According to elemental analyses (Table 6) and DRIFT spectra (Figure 21), the organic
precursors, pyromellitic anhydride (PMDA) and diaminohexane (DAH), are deposited on
aminosilylated silica without significant decomposition. With the deposition of PMDA the
surface density of the nitrogen atoms stays constant, but the surface density of the carbon
atoms increases. At the same time, the C-H vibrations of the aromatic ring of PMDA are seen
above 3000 cm -1 and the change in the chemical environment of N-H bonds is evident from a
broad peak appearing at 3660-3300 cm -1 . Deposition of DAH on PMDA/APDMS/SiO2 causes
a clear increase in the surface density of nitrogen. The peaks in the DRIFT spectra are not
discussed here in detail, but will be treated in a forthcoming paper. 136
The results show that the deposition of multilayered structures, starting from the deposition of
the aminopropylsiloxane network, is fully feasible with ALD. Organic self-assembled
superlattices have earlier been deposited on the planar SiO2 surface by Burtmann et al., 3,4 who
prepared aminosilylated SiO2 <strong>surfaces</strong> in the liquid phase and the actual polyimide layers in
the gas phase by MLD.
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