Metallic conductance is seen in ferroelectric nanodomains

The development is expected to prove useful in the creation of electronics at the nanoscale.

Ferroelectric materials, which switch their polarisation with the application of an electric field, have long been used in devices such as ultrasound machines and sensors. Discoveries about ferroelectrics’ electronic properties are said to be opening up possibilities of applications in nanoscale electronics and information storage.

In a paper published in the American Chemical Society’s Nano Letters, the ORNL-led team demonstrated metallic conductivity in a ferroelectric film that otherwise acts as an insulator.

According to a statement, this phenomenon of an insulator-metal transition was predicted more than 40 years ago by theorists but has eluded experimental proof until now.

‘This finding unambiguously identifies a new conduction channel that percolates through the insulating matrix of the ferroelectric, which opens potentially exciting possibilities to “write” and “erase” circuitry with nanoscale dimensions,’ said lead author Peter Maksymovych, of ORNL’s Center for Nanophase Materials Sciences.

According to ORNL, the ability to use only an electric field as a knob that tunes the magnitude of metallic conductivity in a ferroelectric material and the type of charge carriers is particularly interesting. Doing the latter in a semiconductor would require a change of the material composition.

‘Not only can we turn on metallic conductivity, but if you keep changing the bias dials, you can control the behaviour very precisely,’ said Maksymovych. ‘And the smaller the nanodomain, the better it conducts. All this occurs in the exact same position of the material, and we can go from an insulator to a better metal or a worse metal in a heartbeat or faster. This is potentially attractive for a number of applications and also leads to interesting fundamental questions about the exact mechanism of metallic conductivity.’

Although the researchers focused their study on lead-zirconate titanate, they expect their observations will be applicable for a broader array of ferroelectric materials.

‘We also anticipate that extending our studies onto multiferroics, mixed-phase and anti-ferroelectrics will reveal a whole family of previously unknown electronic properties, breaking new ground in fundamentals and applications alike,’ said co-author and ORNL senior scientist Sergei Kalinin.