Fig. 1: Schematic of exfoliation procedure and summary of exfoliation results for nonlayered binary metal oxides.
a, d Interplanar binding energy (Eb) versus the change in the lattice constant c (Δc). Each point is color-coded based on the absolute value of the integrated crystal orbital Hamilton population (ICOHP). The higher the ICOHP value, the stronger the bonding strength. Insets show the atomic structures of HfO2 and PtO2 under external stretching, from bulk to separation, to reconstruction to form a stable 2D structure. b, c The procedure for calculating Eb. e Eb versus interplanar spacing (dhkl). Materials classified as easily exfoliable, potentially exfoliable, and high binding energy are demonstrated in different colors. The selected 2D oxide dielectrics (five-pointed star), auxetic monolayers (circle), 2D valleytronic oxide (triangle), and the monolayer with the lowest Eb (rectangle) are marked by different symbols and chemical formulas. f Polar histogram for easily/potentially exfoliable 2D stable oxides classified according to space groups. The crystal structure and chemical formula of representative oxide for each space group is given, as well as the total number of 2D oxides contained in the space group. Red spheres denote O atoms and the other colored spheres indicate metal atoms.
