Journal Article 2D materials DFT calculations alloys scanning transmission electron microscopy 2D electrets EELS Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. Ruddlesden-Popper faults STEM atomically thin membranes band structure boron nitride nanosheets boron nitride nanotubes chemical vapor deposition defects density functional theory density-functional theory dialysis and desalting electron energy loss spectroscopy (EELS) electron microscopy electronic properties grain boundaries heterostructures iron-based superconductors lead-halide perovskites liquid cells local magnetic moments magnetic properties