fig2

Figure 2. (A) HfO₂ crystal structures for M-phase (P2₁/c), two non-centrosymmetric O-phases (Pmn2₁ and Pca2₁) and two centrosymmetric O-phases (Pbcm and Pbca) and their atom projections along four major zone axes. (B) STEM-HAADF images of Gd:HfO₂ films acquired along four major zone axes, which are the same for the Pca2₁, Pbca and Pbcm phases. Scale bar is 0.5 nm^[32]. STEM-HAADF: Scanning transmission electron microscopy-high angle annular dark-field.