Nanoscale Structuring in Confined Geometries using Atomic Layer Deposition: Conformal Coating and Nanocavity Formation

Abstract

Nanoscale structuring in confined geometries using atomic layer deposition (ALD) is demonstrated for surfaces of nanochannels in track-etched polymer membranes and in mesoporous silica (SBA-15). Suitable process conditions for conformal ALD coating of polymer membranes and SBA-15 with inorganic oxides (SiO2, TiO2, Al2O3) were developed. On the basis of the oxide-coated layers, nanochannels were further structured by a molecular-templated ALD approach, where calixarene macromolecules are covalently attached to the surface and then embedded into an Al2O3 layer. The removal of calixarene by ozone treatment results in 1–2 nm wide surface nanocavities. Surfaces exposed to different process steps are analyzed by small angle X-ray scattering (SAXS) as well as by X-ray photoelectron and infrared spectroscopy. The proposed nanostructuring process increases the overall surface area, allows controlling the hydrophilicity of the channel surface, and is of interest for studying water and ion transport in confinement.

2H NMR Studies on the Dynamics of Pure and Mixed Hydrogen-Bonded Liquids in Confinement

“…Details can be found in another contribution to this issue [34]. Moreover, atomic layer deposition was employed by the Hess group (TU Darmstadt) to alter the chemical structure of the inner surfaces for some of the used MCM-41 materials, specifically, to deposit Al 2 O 3 layers, as again detailed in another contribution to this issue [35]. [35].…”

Conical Nanotubes Synthesized by Atomic Layer Deposition of Al2O3, TiO2, and SiO2 in Etched Ion-Track Nanochannels

“…The self-limiting nature of the chemical reactions provides excellent thickness control, even in deeply embedded surfaces such as the inner wall of nanopores and nanochannels. In recent years, conformal TiO 2 , SiO 2 , and Al 2 O 3 coating of cylindrical nanochannels in porous alumina membranes [ 6 , 7 ] and in etched ion-track polycarbonate membranes with aspect ratios (length over diameter) up to 3000 [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ] was demonstrated. In the latter case, specific low-temperature ALD processes ensured the thermal stability of the polymer material [ 14 , 15 ].…”

Roughness Effect on the Pull-Off Force between Two Surfaces with Water Adsorbed between Them. A Molecular Dynamics Simulation Perspective

“…Theses nanocavities have been also synthesized into nanochannels in membranes. 32 The formation of these cavities was demonstrated by AFM. 33 Equation 1 assumes that the pull-off force contains all the forces, but here it has shown that water layers between the substrates do not allow van der Waals forces to be present (because the required distance is not reached); therefore, F pull ≠ F vdw + F sol for this case.…”

“…With this method, Canlas et al created nanocavities almost cylindrical of diameter 2 nm and 0.4–0.7 nm depth on TiO 2 surfaces. Theses nanocavities have been also synthesized into nanochannels in membranes . The formation of these cavities was demonstrated by AFM …”