Figure 9.

TEM images of nanopores before (top row) and after (below row) deposition of Al₂O₃ coatings by ALD. A square nanopore (a) before and (b) after 500 layers of Al₂O₃ coating. A circular pore with its initial diameter of 21.6 nm (c) before and (d) after 70 layers of Al₂O₃ coating to produce a ~4.8 nm pore. A nanopore with its initial diameter of ~7 nm (e) before and (f) after 24 layers of Al₂O₃ coating to produce a ~2 nm pore (reprinted with permission from [103], copyright 2004, American Chemical Society).