Aw. Ott et al., MODIFICATION OF POROUS ALUMINA MEMBRANES USING AL2O3 ATOMIC LAYER CONTROLLED DEPOSITION, Chemistry of materials, 9(3), 1997, pp. 707-714
Al2O3 films were deposited with atomic layer control inside the pores
of Anodisc alumina membranes. To achieve this controlled deposition on
a high aspect ratio structure, a binary reaction for Al2O3 chemical v
apor deposition (2Al(CH3)(3) + 3H2O --> Al2O3 + 6CH(4)) was separated
into two half-reactions: (A) AlOH + Al(CH3)(3) --> Al-O-Al(CH3)(2)* CH4 and (B) AlCH3 + H2O --> AlOH* + CH4, where the asterisks designa
te the surface species. The trimethylaluminum [Al(CH3)(3)] (TMA) and H
2O reactants were employed alternately in an ABAB... binary reaction s
equence to deposit the Al2O3 film Because each half-reaction is self-l
imiting, atomic layer controlled Al2O3 deposition was achieved on the
surface of the high aspect ratio pores. To determine the necessary rea
ction conditions, surface species during each half-reaction were perio
dically monitored using in situ transmission FTIR spectroscopy. Ex sit
u gas flux and permporometry measurements were also performed to deter
mine the effect of the binary reaction sequence on the pore diameter.
Gas flux measurements for H-2 and N-2 were consistent with a progressi
ve pore size reduction versus the number of AB reaction cycles. The pe
rmporometry measurements showed that the original pore diameter of sim
ilar to 220 Angstrom was reduced to similar to 140 Angstrom after 120
AB reaction cycles.