Fig. 3: Structural phase identification and distribution analysis of ultrathin HZO membranes.
A Plan-view HAADF-STEM image of a grain with the o-(111) structure in the 5-nm-thick HZO membrane. The inset is the magnified part of the red square frame. B Atomic arrangement and simulated HAADF-STEM image of o-(111) HfO2. C Plan-view HAADF-STEM image of a grain with the r-(111) structure in the 1-nm-thick HZO membrane. The inset is the magnified part of the orange square frame. D Atomic arrangement and simulated HAADF-STEM image of r-(111) HfO2. The scale bars in A and C denote 1 nm. E–G Plan-view HAADF-STEM images and structural phase distribution analysis of (E) 5-nm-, (F) 3-nm-, and (G) 1-nm-thick HZO membranes. The grains having r-(111), o-(111), o-(001), and m-(−111) atomic arrangements are colored in orange, red, green, and blue, respectively. The (001)-oriented grains circled with dashed green lines in F and G show almost no periodic modulation in the distance between neighboring Hf/Zr atoms characteristic of the o-(001) structure. The grains not circled are ones whose structural phases cannot be identified. The scale bars in E–G denote 5 nm. H–J SAED patterns for (H) 5-nm-, (I) 3-nm-, and (J) 1-nm-thick HZO membranes. The diffraction patterns are colored with the same color codes as in (E-G) to identify which diffraction patterns originate from which structural phases of HZO. Insets are the high-contrasted parts of the SAED. K Normalized diffraction intensity profiles versus reciprocal distance extracted from the SAED patterns in H–J. The colors of the arrows represent the structural phases that mainly contribute to the arrowed peaks and share the same color code as is used in E–G.
