Fig. 3

Mircoscopy of graphene barrier films. a SEM image of continuous growth of 10 nm AlO _x on a single graphene grain (dotted area) on Cu foil after 1st growth and a representative magnified area in (b). The cross-sectional HRTEM image in c shows the presence of few layer graphene below the AlO _x -based layer after the 2nd growth, as illustrated in the inset. d Bright field TEM image of a suspended RGA film in plan-view, showing the nanocrystalline nature of the AlO _x -based phase after the 2nd growth step. The inset shows the corresponding SAED pattern, which consists of sets of hexagonally arranged spots assigned to few layer graphene and a ring pattern corresponding to a nanocrystalline phase of the Al-oxycarbide Al₂OC, as described in Supplementary Fig. 3. e Schematic highlighting the nanolaminate structure and coverage of graphene defects by AlO _x -based layer. The scale bar in a is 10 μm, b is 0.5 μm, c is 5 nm, and d is 100 nm