Zhang Lei, Tang Cheng, Zhang Chunmei, Du Aijun
School of Chemistry and Physics, Queensland University of Technology, Gardens Point Campus, Brisbane, QLD 4000, Australia.
Shanxi Key Laboratory for Theoretical Physics Frontiers, Institute of Modern Physics, Northwest University, Xi'an 710069, P. R. China.
Nanoscale. 2020 Oct 29;12(41):21291-21298. doi: 10.1039/d0nr06609e.
Out-of-plane ferroelectricity in the two-dimensional (2D) regime shows great promise for applications in next-generation electronic devices but has been rarely reported. Herein, by using high-throughput search and density functional theory (DFT) calculations, three types of ferroelectric MXene phases (type-I: Nb2CS2 and Ta2CS2; type-II: Sc2CO2 and Y2CO2; and type-III: Sc2CS2 and Y2CS2) are for the first time predicted to be achievable by surface functionalization of 2D MXenes. The identified 2D ferroelectric MXenes not only demonstrate remarkable and reversible spontaneous electric polarization along both the out-of-plane and in-plane orientations but also exhibit giant out-of-plane and in-plane piezoelectric response to the external strain. More excitingly, the type-III ferroelectric MXenes possess rare out-of-plane auxeticity that can be triggered by the tensile strain along both the zig-zag and the arm-chair directions. The intriguing ferroelectricity, large piezoelectric response, and auxeticity render the ferroelectric MXenes versatile candidates for nanoscale electronic and mechanic devices.
二维体系中的面外铁电性在下一代电子器件应用中展现出巨大潜力，但相关报道却很少。在此，通过高通量搜索和密度泛函理论（DFT）计算，首次预测出三种类型的铁电MXene相（I型：Nb2CS2和Ta2CS2；II型：Sc2CO2和Y2CO2；III型：Sc2CS2和Y2CS2）可通过二维MXene的表面功能化实现。所确定的二维铁电MXene不仅沿面外和面内方向表现出显著且可逆的自发极化，还对外加应变展现出巨大的面外和面内压电响应。更令人兴奋的是，III型铁电MXene具有罕见的面外负泊松比特性，可通过沿锯齿形和扶手椅形方向的拉伸应变触发。这种有趣的铁电性、大压电响应和负泊松比特性使铁电MXene成为纳米级电子和机械器件的多功能候选材料。
