Sliding and moiré ferroelectricity are new types of ferroelectricity from switchable polarization between layers of bidimensional materials, that are kept together by weak van der Waals forces, and can therefore slide or tilt with respect to each other. This type of ferroelectricity is studied on bi- or tri-layers with sophisticated techniques at the nanoscopic scale and, thanks to its robustness and low coercive field, it promises great advances in nanoelectronics, especially FeRAMs. We present measurements of the dynamic Young's modulus of self-standing thick films of Ti3C2Tx MXene, which reveal a phase transition as a steplike softening and increase of the mechanical losses below 350 K (Fig. 1). This type of elastic anomaly is typical of phase transitions, where the square of the order parameter is coupled to strain. It is argued that, in spite of the metallic character of the MXene monolayers, it should be a ferroelectric transition, most likely of the sliding (moiré) type, due to charge transfer between the flakes, that slide with respect to each other. The interlayer nature of the transition is reinforced by the observation that it is suppressed by intercalation of water between the layers [1]. If the transition were confirmed to be sliding ferroelectricity, it would be the first time that such a phenomenon is found in a MXene, and it would be demonstrated that it can also be studied with simple macroscopic methods. In addition, thanks to the insensitiveness of the elastic response to the free charges, the temperature dependence of the Young's modulus can reveal a ferroelectric transition also in electrically conducting materials, where probing the polarization is impossible with traditional methods.
"Phase transition in thick metallic films of Ti3C2Tx MXene: possible sliding ferroelectricity" comunicazione orale su invito alla International Conference on Physics of Two-Dimensional Crystals, ICP2DC 2024 Belgrade - Serbia, July 2nd - 6th, 2024
Francesco Cordero
;Aldo Di Carlo;
2024
Abstract
Sliding and moiré ferroelectricity are new types of ferroelectricity from switchable polarization between layers of bidimensional materials, that are kept together by weak van der Waals forces, and can therefore slide or tilt with respect to each other. This type of ferroelectricity is studied on bi- or tri-layers with sophisticated techniques at the nanoscopic scale and, thanks to its robustness and low coercive field, it promises great advances in nanoelectronics, especially FeRAMs. We present measurements of the dynamic Young's modulus of self-standing thick films of Ti3C2Tx MXene, which reveal a phase transition as a steplike softening and increase of the mechanical losses below 350 K (Fig. 1). This type of elastic anomaly is typical of phase transitions, where the square of the order parameter is coupled to strain. It is argued that, in spite of the metallic character of the MXene monolayers, it should be a ferroelectric transition, most likely of the sliding (moiré) type, due to charge transfer between the flakes, that slide with respect to each other. The interlayer nature of the transition is reinforced by the observation that it is suppressed by intercalation of water between the layers [1]. If the transition were confirmed to be sliding ferroelectricity, it would be the first time that such a phenomenon is found in a MXene, and it would be demonstrated that it can also be studied with simple macroscopic methods. In addition, thanks to the insensitiveness of the elastic response to the free charges, the temperature dependence of the Young's modulus can reveal a ferroelectric transition also in electrically conducting materials, where probing the polarization is impossible with traditional methods.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
