Modification of Porous Alumina Membranes Using Al2O3 Atomic Layer Controlled Deposition

Abstract

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 vapor deposition (2A1(CH3)3 + 3H2O → Al2O3 + 6CH4) was separated into two half-reactions: (A) AlOH* + A1(CH3)3 → A1-O-A1(CH3)2* + CH4 and (B) AlCH3* + H2O → AlOH* + CH4, where the asterisks designate the surface species. The trimethylaluminum [Al(CH3)3] (TMA) and H2O reactants were employed alternately in an ABAB... binary reaction sequence to deposit the Al2O3 film. Because each half-reaction is self-limiting, atomic layer controlled Al2O3 deposition was achieved on the surface of the high aspect ratio pores. To determine the necessary reaction conditions, surface species during each half-reaction were periodically monitored using in situ transmission FTIR spectroscopy. Ex situ gas flux and permporometry measurements were also performed to determine the effect of the binary reaction sequence on the pore diameter. Gas flux measurements for H2 and N2 were consistent with a progressive pore size reduction versus the number of AB reaction cycles. The permporometry measurements showed that the original pore diameter of ∼220 Å was reduced to ∼140 Å after 120 AB reaction cycles. Show more