Extended Data Fig. 2: Ferroelectricity of the 2 nm thick HZO grown on silicon.
From: Negative differential capacitance in ultrathin ferroelectric hafnia
a, TEM-PED phase mapping result for the 2 nm thick HZO, exhibiting the orthorhombic (O) phase (green; 80 %) dominant crystal structure with minor fraction of the tetragonal (T) phase. b, In-plane XRD for the same sample is presented, where the obtained spectrum could be reproduced quantitatively well by fitting with the orthorhombic (84 %) and tetragonal phases (16 %) (the grey line shows the negligible difference between the measurement and fitting). Green (orthorhombic) and blue (tetragonal) bars indicate the diffractions used to fit the data. The result shows that most of the area (84%) exhibits the orthorhombic structure. Again, the population of orthorhombic and tetragonal phases obtained in two independent measurements with different length scales in (a) and (b) are quantitatively comparable. c, PFM amplitude and phase hysteresis loops. Butterfly shaped amplitude (upper panel) accompanying 180° phase shift (lower panel) indicates the existence of spontaneous polarization states switchable by an electric-field. Similar to the analyses for the 4 nm thick HZO in Extended Data Fig. 1, all the results obtained for the 2 nm thick HZO films are also consistent, indicating the ferroelectric character.
