Fig. 1: Polar structure and ferroelectric polarization.
a AFM, SEM, TEM topographical images and the AFM height profile of a Te nanowire on a SiO2/Si wafer. b STEM images of the Te nanowire viewed along b- and c-axes (lower left insets here as well as in (a) show axes projected into the image planes; left and right insets show atomic lattice models). e is the epitaxial direction of inclined stepwise planes. c Ferroelectric switching pathway of 4L Te from α- to α′-state calculated using the NEB method. Insets display the atomic structures of α and α′, representing two opposite polarization states, as well as the paraelectric nonpolar β-state. d Differential charge density (Δρ) of 4L Te for α-, β- and α′-states. Here Δρ = ρ(tot) − ρ(c-Te) − ρ(n-Te), where ρ(tot) is the total charge density, ρ(c-Te) is the charge density of the LCAs (c) and ρ(n-Te) is the charge density of the neighboring (n) Te atoms. Red and blue colors represent the charge accumulation and depletion, respectively. The isosurface values in α- (α′-) and β-states are set to 0.007 and 0.006 e/bohr3, respectively. The arrows denote the polarization direction. Dotted rectangular boxes in (c) and (d) indicate the smallest repeatable unit in the periodic lattice. e Calculated polarization per layer for the α-state Te with different number of layers.
