First observation of ferroelectric metal native

In an article published today in Progress of scienceUNSW researchers describe the first observation of a native ferroelectric metal.

The study represents the first example of a native metal with bistable and electrically switchable spontaneous polarization states – the hallmark of ferroelectricity.

"We found a coexistence of native metallicity and ferroelectricity in crystalline tungsten ditelluride bulk (WTe²) at room temperature, "says author of the study, Dr. Pankaj Sharma.

"We have demonstrated that the ferroelectric state is switchable under an external electrical bias and explain the mechanism of" metallic ferroelectricity "in WTe² through a systematic study of crystal structure, electronic transport measurements and theoretical considerations. "

"A van der Waals material that is both metallic and ferroelectric in its bulk crystalline form at room temperature has potential for new applications in nanoelectronics," says author, Dr. Feixiang Xiang.

Ferroelectricity can be considered as an analogy with ferromagnetism. A ferromagnetic material has permanent magnetism and, in the words of the people, is simply a "magnet" with a north pole and a south pole. The ferroelectric material also has a similar electrical property called permanent electric polarization, which comes from electric dipoles consisting of equal ends or poles, but of opposite charge. In ferroelectric materials, these electric dipoles exist at the level of the elementary cell and give rise to a non-zero permanent electrical dipole moment.

This spontaneous electrical dipole moment can be the object of a repeated transition between two or more states or equivalent directions when applying an external electric field – property used in many ferroelectric technologies , such as nanoelectronic computer memory, RFID cards, medical ultrasound transducers, infrared cameras, underwater sonar, vibration and pressure sensors, and precision actuators.

Conventionally, ferroelectricity has been observed in insulating or semiconducting rather than metallic materials, since the conduction electrons in the metals mask the static internal fields resulting from the dipole moment.

A ferroelectric half-metal at room temperature has been published in Progress of science in July 2019.

Monocrystalline tungsten ditelluride in bulk (WTe)²), belonging to a class of materials known as transition metal dichalcogenides (TMDCs), was probed by spectroscopic measurements of electrical transport by conductive atomic force microscopy (c-AFM) to confirm its metallic behavior and by piezo-reactive force microscopy (PFM) to map the polarization, detecting lattice deformation due to an applied electric field.

The ferroelectric domains – that is, the opposite polarization direction regions – were visualized directly in the freshly cleaved WTe² Single crystals.

Spectroscopic PFM measurements with a top electrode in a capacitor geometry were used to demonstrate the switching of the ferroelectric polarization.

The study was funded by the Australian Research Council through the ARC Center of Excellence on Future Energy Efficient Electronic Technologies (FLEET), and work was partly done with the help of NSW Nodes facilities of the Australian National Manufacturing Facility. assistance from the Australian Government Research Training Program Scholarship Program.

Calculations of the Functional Density Theory (DFT) According to First Principles (University of Nebraska) confirmed the experimental results of the electronic and structural origins of ferroelectric instability of WTe², supported by the National Science Foundation.

Ferroelectric materials are the subject of extensive study at FLEET (ARC's center of excellence on future energy-efficient electronic technologies) for their potential use in electronic products at Low power consumption, beyond CMOS technology.

The switchable electric dipole moment of ferroelectric materials could for example serve as a gate for the underlying 2D electron system in an artificial topological insulator.

Compared with conventional semiconductors, the very close proximity (below the nanometer) of the electron dipole moment of a ferroelectric to the electron gas in the atomic crystal ensures a more efficient switching, thus exceeding the limits of conventional semiconductors in which the conductive channel is buried at tens of nanometers. area.

Topological materials are being studied as part of FLEET's research theme 1, which aims to establish ultra-low-resistance electronic tracks to create a new generation of ultra-low-energy electronics.

FLEET is a CRA – funded research center that brings together more than a hundred Australian and international experts to develop a new generation of very low – energy electronics, motivated by the need for reduce the energy consumed by the computer.

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* Dr. Pankaj Sharma [email protected]

* Teacher. Jan Seidel [email protected]

* Dr. Feixiang Xiang [email protected]

* Professor Alexander Hamilton [email protected]