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 (2Al(CH3)3 + 3H2O → Al2O3 + 6CH4) 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 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.

Investigating the Trimethylaluminium/Water ALD Process on Mesoporous Silica by In Situ Gravimetric Monitoring

“…On the other hand, the Al surface concentration of our synthesized samples can be straightforwardly calculated from the Al content and the BET surface area. Though, the assumption of a two-dimensional growth of the AlO x process needs to be made, meaning TMA preferably reacted with the original SiO 2 surface rather than the AlO x islands [33]. The Al-O species are consequently arranged side by side and not on top of each other.…”

Supramolecular Organization of Polymeric Materials in Nanoporous Hard Templates

“…The degree of geometric confinement can be adjusted by the D p -value. The chemical properties of the rigid pore walls of the hard template can by modified too, for example, by silanization or atomic layer deposition [21,22]. The high surfaceto-volume ratio of the nanoporous hard templates makes it possible to control self-assembly processes by adjusting the properties of the pore walls.…”

Template‐Assisted Fabrication of Dense, Aligned Arrays of Titania Nanotubes with Well‐Controlled Dimensions on Substrates

“…ALD has also been used to narrow the pore diameter in nanoporous alumina. [26,27] We have chosen porous anodic alumina as the template material for producing nanotube arrays because it is easy to produce over large areas, has a high density of tunable-diameter pores, and is thermally stable. The pore diameter and spacing are determined by the acidic solution employed and the voltage applied during anodization.…”