Journal Article Research Support, Non-U.S. Gov't (6,6)-phenyl C61-butyric acid methyl ester 2D materials 3D structure Fullerenes Imides Polymers atom probe microscopy conductive filaments cross-point array epitaxial self-planarization metal chalcogenides metal-insulator transition non-volatilememory phase transformations resistive switching titanium oxide transfer-free device fabrication transmission electron microscopy two-terminal switch wafer-scale single-crystal thin films