Abstract
Beyond a ferroelectric critical thickness of several nanometers existed in conventional ferroelectric perovskite oxides, ferroelectricity in ultimately thin dimensions was recently discovered in SnTe monolayers. This discovery suggests the possibility that SnTe can sustain ferroelectricity during further low-dimensional miniaturization. Here, we investigate a ferroelectric critical size of low-dimensional SnTe nanostructures such as nanoribbons (1D) and nanoflakes (0D) using first-principle density-functional theory calculations. We demonstrate that the smallest (one-unit-cell width) SnTe nanoribbon can sustain ferroelectricity and there is no ferroelectric critical size in the SnTe nanoribbons. On the other hand, the SnTe nanoflakes form a vortex of polarization and lose their toroidal ferroelectricity below the surface area of 4 × 4 unit cells (about 25 Å on one side). We also reveal the atomic and electronic mechanism of the absence or presence of critical size in SnTe low-dimensional nanostructures. Our result provides an insight into intrinsic ferroelectric critical size for low-dimensional chalcogenide layered materials.
Highlights
Ferroelectrics exhibit spontaneous polarization that can be reversed by an external electric field, due to their noncentrosymmetric crystal structure having a relative displacement of cations and anions in a ferroelectric (FE) phase
We investigate whether a ferroelectric critical size exists in low-dimensional structure of SnTe, the nanoribbons (1D) and nanoflakes (0D) using first-principle, density-functional theory (DFT) calculations
We focus on SnTe nanoribbons and nanoflakes with an edge structure
Summary
Ferroelectrics exhibit spontaneous polarization that can be reversed by an external electric field, due to their noncentrosymmetric crystal structure having a relative displacement of cations and anions in a ferroelectric (FE) phase. When the material dimensions become nanoscale, the ratio of the surface or edge to the entire volume increases, the influence of the depolarization field formed by the surface charge becomes dominant, and the ferroelectricity of the entire material disappears The long-range interaction is reduced due to the absence of atoms outside of material surfaces, and thereby the balance between long-range and short-range interaction is broken Such interactions are changed due to the reconstruction and rearrangement of atomic and electronic structures at surfaces or edges. Ferroelectricity was discovered in the monolayer structure of chalcogenide SnTe in the in-plane direction [18] This indicates that ferroelectricity can exist in a structure with an atomic thickness. We investigate whether a ferroelectric critical size exists in low-dimensional structure of SnTe, the nanoribbons (1D) and nanoflakes (0D) using first-principle, density-functional theory (DFT) calculations
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