Atomic layer deposition enables multi-modal three-dimensional electron microscopy of isoporous membranes

Area of Science:

• Materials Science
• Nanotechnology
• Water Treatment

Background:

• Block copolymers (BCPs) are key for fabricating isoporous membranes for water purification.
• Conventional electron microscopy (EM) techniques (SEM, TEM) require external contrast agents due to low BCP domain contrast.
• Existing EM methods are limited to surface or cross-sectional analysis, hindering full structural understanding.

Purpose of the Study:

• To develop a method for internal contrast enhancement in BCPs for advanced 3D characterization.
• To enable detailed 3D structural analysis of BCP membranes for water purification.
• To correlate 3D membrane structure with performance for improved design.

Main Methods:

• Selective growth of aluminum oxide (AlO) within the pore-forming domains of BCPs to create intrinsic contrast.
• Utilizing focused ion beam scanning electron microscopy (FIB-SEM) and transmission electron microscopy (TEM) tomography for 3D imaging.
• Analysis of 3D pore geometry, tortuosity, and permeability.

Main Results:

• Achieved stable, internal contrast in BCPs via selective AlO growth.
• Enabled high-resolution 3D characterization of membrane architecture.
• Provided detailed insights into 3D pore structure, tortuosity, and permeability.

Conclusions:

• The AlO-enhanced contrast method allows comprehensive 3D structural analysis of BCP membranes.
• This advanced characterization improves the understanding of structure-property relationships.
• Facilitates better design and optimization of BCP membranes for water purification applications.