Room-Temperature Ferroelectricity in 2D Metal–Tellurium–Oxyhalide Cd₇Te₇Cl₈O₁₇ via Selenium-Induced Selective-Bonding Growth

Abstract

Two-dimensional (2D) ferroelectric materials have attracted increasing interest due to meeting the requirements of integration, miniaturization, and multifunction of devices. However, the exploration of intrinsic 2D ferroelectric materials is still in the early stage, for which the related reports are still limited, especially fewer ones prepared by chemical vapor deposition (CVD). Here, the ultrathin metal−tellurium− oxyhalide Cd 7 Te 7 Cl 8 O 17 (CTCO) flakes as thin as 3.8 nm are realized via the selenium-induced selective-bonding CVD method. The growth mechanism has been confirmed by experiments and theoretical calculations, which can be ascribed to the induction of selective bonding of a hydrogen atom in H 2 O molecules by the introduction of selenium, leading to the generation of strong oxidants. Excitingly, switchable out-of-plane ferroelectric polarization was observed in CTCO flakes down to 6 nm at room temperature, which may be caused by mobile Cl vacancies. This work has implications for the synthesis and applications of 2D ferroelectric materials.

Periodic Ferroelectric Stripe Domains in α-In2Se3 Nanoflakes Grown via Reverse-Flow Chemical Vapor Deposition

“…Under the power of 49.4 mW, the SHG intensity is the highest. Figure b,c shows that the SHG intensity is the power-dependent quadratic square relationship, and the red line is the fitted equation I ∝ P . ,,, In addition, the sample was rotated by fixing the polarization to produce s-in/s-out and s-in/p-out configurations to study the polarization-dependent second harmonic spectra. The incident laser is generated with a femtosecond pulsed laser at a wavelength of 800 nm, the laser is parallel to the polarization direction, and the azimuthal dependence of the SHG intensity is detected on the CVD sample.…”

Progress on Emerging Ferroelectric Materials for Energy Harvesting, Storage and Conversion

“…Thus, synergistic contributions of local charge redistribution, ionic displacement and even vacancy location play important roles in generating ferroelectricity. [69,70,204,205] Ferrielectric CuInP 2 S 6 , with T C = 315 K and E g = 1.503 eV, [206] is a representative 2D vdW material for exploration of unusual ferroelectricity and multi-functional device applications. [207,208] In structure, Cu and In atoms undergo opposite displacements within each layer along z direction and paired P-P atoms fill in [173] Copyright 2019, AAAS.…”

High-TC Two-Dimensional Ferroelectric CuCrS2 Grown via Chemical Vapor Deposition

“…Compared with traditional ferroelectrics, 2D ferroelectrics exhibit stable ferroelectricity even at a single layer and have a stable interface with less dangling bonds to integrate with other materials, which are critical to explore physics at the nanometer scale. Although there are several theoretical predictions of 2D ferroelectrics, only a few of them have been experimentally verified ( e.g ., CuInP 2 S 6 , SnTe, WTe 2 , In 2 Se 3 ). − Up to now, the majority of the 2D ferroelectrics have had a low ferroelectric transition temperature ( T C ) (usually below 500 K), hindering their applications. Moreover, most of the reported 2D ferroelectrics are prepared by mechanical exfoliation, resulting in nonuniform thickness, area, and shape, which is not proper for large-scale applications in the future.…”