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

Abstract

Block copolymer (BCP) membranes are promising materials for water purification. They enable the fabrication of integral asymmetric isoporous membranes with high permeability and good selectivity. Commonly, the characterization of such...

Revealing the 3D Structure of Block Copolymers with Electron Microscopy: Current Status and Future Directions

“…As mentioned in the previous sections, the use of both methods on the same type of BCP specimen to supply complementary information has been demonstrated. 104,107,112,115 However, to the best of our knowledge, the combination of both methods has never methods been performed at the exact same location in one specimen. Such a comparison can be used to better pinpoint each method's shortcomings and enhance reconstruction capabilities.…”

“…Thomas and co-workers drastically increased the resolution along the slicing dimension by optimizing milling conditions so that each slice was ∼3 nm thick. ,, This considerably higher resolution enabled imaging of a smaller period polymer (120–130 nm period, with ∼20 nm feature size), opening the path for the FIB/SEM study of smaller features (Figure b). In a more recent work, Simon et al imaged PS- b -P4VP asymmetric porous membranes with 5 nm z slices . They used SIS (see section 2.6 for more information on SIS) to stain the P4VP domains with AlO x , and in doing so introduced SEM imaging contrast that had not been present in the native BCP.…”

“…Radiation-sensitive BCPs can benefit from DED, since with these detectors, one can work at a much lower electron dose compared to conventional CCD, working at doses of a single electron per Å 2 . For example, we recently probed the 3D structure of asymmetric ultrafiltration BCP membranes using TEMT with doses of ∼5 e/Å 2 …”

“…In a more recent work, Simon et al imaged PS-b-P4VP asymmetric porous membranes with 5 nm z slices. 115 They used SIS (see section 2.6 for more information on SIS) to stain the P4VP domains with AlO x , and in doing so introduced SEM imaging contrast that had not been present in the native BCP. The FIB/SEM tomography allowed for precise mapping of the tortuous 3D pores formed during self-assembly and non-solvent-induced phase separation.…”

“…For example, we recently probed the 3D structure of asymmetric ultrafiltration BCP membranes using TEMT with doses of ∼5 e/Å 2 . 115 4.2. Scanning TEM.…”