Nav: Home

First observation of native ferroelectric metal

July 05, 2019

In a paper released today in Science Advances, UNSW 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 coexistence of native metallicity and ferroelectricity in bulk crystalline tungsten ditelluride (WTe2) at room temperature," explains study author Dr Pankaj Sharma.

"We demonstrated that the ferroelectric state is switchable under an external electrical bias and explain the mechanism for 'metallic ferroelectricity' in WTe2 through a systematic study of the 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 nano-electronics applications," says author Dr Feixiang Xiang.

FERROELECTRIC BACKGROUNDER

Ferroelectricity can be considered an analogy to ferromagnetism. A ferromagnetic material displays permanent magnetism, and in layperson's terms, is simply, a 'magnet' with north and south pole. Ferroelectric material likewise displays an analogous electrical property called a permanent electric polarisation, which originates from electric dipoles consisting of equal, but oppositely charged ends or poles. In ferroelectric materials, these electric dipoles exist at the unit cell level and give rise to a non-vanishing permanent electric dipole moment.

This spontaneous electric dipole moment can be repeatedly transitioned between two or more equivalent states or directions upon application of an external electric field - a property utilised in numerous ferroelectric technologies, for example nano-electronic computer memory, RFID cards, medical ultrasound transducers, infrared cameras, submarine sonar, vibration and pressure sensors, and precision actuators.

Conventionally, ferroelectricity has been observed in materials that are insulating or semiconducting rather than metallic, because conduction electrons in metals screen-out the static internal fields arising from the dipole moment.

THE STUDY

A room-temperature ferroelectric semimetal was published in Science Advances in July 2019.

Bulk single-crystalline tungsten ditelluride (WTe2), which belongs to a class of materials known as transition metal dichalcogenides (TMDCs), was probed by spectroscopic electrical transport measurements, conductive-atomic force microscopy (c-AFM) to confirm its metallic behaviour, and by piezo-response force microscopy (PFM) to map the polarisation, detecting lattice deformation due to an applied electric field.

Ferroelectric domains - ie, the regions with oppositely oriented direction of polarization - were directly visualised in freshly-cleaved WTe2 single crystals.

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

The study was supported by funding from the Australian Research Council through the ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), and the work was performed in part using facilities of the NSW Nodes of the Australian National Fabrication Facility, with the assistance of the Australian Government Research Training Program Scholarship scheme.

First-principles density functional theory (DFT) calculations (University of Nebraska) confirmed the experimental findings of the electronic and structural origins of the ferroelectric instability of WTe2, supported by the National Science Foundation.

FERROELECTRIC STUDIES AT FLEET

Ferroelectric materials are keenly studied at FLEET (the ARC Centre of Excellence in Future Low-Energy Electronics Technologies) for their potential use in low-energy electronics, 'beyond CMOS' technology.

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

In comparison with conventional semiconductors, the very close (sub-nanometre) proximity of a ferroelectric's electron dipole moment to the electron gas in the atomic crystal ensures more effective switching, overcoming limitations of conventional semiconductors where the conducting channel is buried tens of nanometres below the surface.

Topological materials are investigated within FLEET's Research theme 1, which seeks to establish ultra-low resistance electronic paths with which to create a new generation of ultra-low energy electronics.

FLEET is an ARC-funded research centre bringing together over a hundred Australian and international experts to develop a new generation of ultra-low energy electronics, motivated by the need to reduce the energy consumed by computing.
-end-
CONTACTS

* Dr Pankaj Sharma pankaj.sharma@unsw.edu.au

* Prof Jan Seidel jan.seidel@unsw.edu.au

* Dr Feixiang Xiang feixiang.xiang@unsw.edu.au

* Prof Alexander Hamilton alex.hamilton@unsw.edu.au

ARC Centre of Excellence in Future Low-Energy Electronics Technologies

Related Ferroelectric Articles:

Scientists help thin-film ferroelectrics go extreme
Scientists have created the first-ever polarization gradient in thin-film ferroelectrics, greatly expanding the range of functional temperatures for a key material used in a variety of everyday applications.
A new approach to improving lithium-sulfur batteries
Researchers from the University of Delaware and China's Northwestern Polytechnical University, Shenzhen University and Hong Kong Polytechnic University have demonstrated a new polysulfide entrapping strategy that greatly improves the cycle stability of Li-S batteries.
New study of ferroelectrics offers roadmap to multivalued logic for neuromorphic computing
Research published Wednesday in Nature Scientific Reports lays out a theoretical map to use ferroelectric material to process information using multivalued logic -- a leap beyond the simple ones and zeroes that make up our current computing systems that could let us process information much more efficiently.
Material can turn sunlight, heat and movement into electricity -- all at once
Many forms of energy surround you: sunlight, the heat in your room and even your own movements.
New material with ferroelectricity and ferromagnetism may lead to better computer memory
Scientists at Tokyo Institute of Technology (Tokyo Tech) have demonstrated that ferroelectricity and ferromagnetism coexist at room temperature in thin films of bismuth-iron-cobalt oxide.
Ultra-thin ferroelectric material for next-generation electronics
Scientists at Tokyo Institute of Technology have demonstrated the potential of a new, thin-film ferroelectric material that could improve the performance of next-generation sensors and semi-conductors.
Physicists 'dissolve' water in an emerald
Scientists have detected ferroelectric properties of water molecules by placing them into a network of nanoactivities in a crystal.
Study yields new knowledge about materials for ultrasound and other applications
Scientists at the Department of Energy's Oak Ridge National Laboratory and their research partners have used neutron scattering to discover the key to piezoelectric excellence in the newer materials, which are called relaxor-based ferroelectrics.
Plastic crystals could improve fabrication of memory devices
A novel 'plastic crystal' developed by Hokkaido University researchers has switching properties suitable for memory-related applications.
Integration of novel materials with silicon chips makes new 'smart' devices possible
Materials researchers have developed a way to integrate novel functional materials onto a computer chip, allowing the creation of new smart devices and systems.

Related Ferroelectric Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...