- The new ferroelectric capacitor built in the lab could survive 10 billion rewrite cycles.
- Unlike existing flash drives, ferroelectric memory devices could withstand cosmic ray exposure and even operate in outer space.
The concept for nonvolatile memory devices utilizing ferroelectric thin sheets with electrically switchable spontaneous polarization has a huge potential owing to very low power consumption, high writing speed, and theoretically unlimited endurance.
Today, the electronic industry is pursuing new nonvolatile memory technologies to achieve longer lifetimes and faster access speeds than existing solid-state and flash drives. One of the promising candidates is hafnium dioxide-based memory. It uses a dielectric material that is already known to the microelectronics industry.
Under specific temperature treatment and alloying, some thin hafnium dioxide layer can form metastable crystals that exhibit ferroelectric properties. This means these crystals can ‘memorize’ the direction of the electric field applied to them.
The structure of this new memory cell (zirconium-hafnium oxide film) resembles an ordinary electric capacitor. It is approximately 10 nanometers thick, interposed between two electrodes.
The remnant polarization of the ferroelectric capacitors has to be maximized so that they can be used as memory cells. However, to ensure that, researchers have to deeply understand the processes that occur in the thin film. This involves measuring the electric potential distributed across the nanofilm.
Breakthrough on the way to new nonvolatile memory types
Although the ferroelectric phase in hafnium oxide was discovered a decade ago, scientists haven’t been able to directly measure its potential distribution at the nanoscale yet.
Now, researchers at the Moscow Institute of Physics and Technology have come up with a unique technique for determining the electric potential distribution across a ferroelectric capacitor.
They used hard X-ray photoemission spectroscopy to probe the memory capacitor. The technique relies on the standing-wave mode of the strong monochromatic X-ray beam. It measures the local electrostatic potential by examining the core-level line shifts.
The findings show the electric potential profile across the zirconium-hafnium oxide layer is non-linear and alters with polarization switching.
A conventional SSD
Researchers combined the data from scanning transmission electron microscopy with theoretical modeling and explained the observed non-linear potential behavior in terms of defects in zirconium-hafnium oxide, at both interfaces, and their charge state modulated by the ferroelectric polarization.
In summary, the study sheds new light on the intrinsic electronic properties of hafnium oxide-based ferroelectric capacitors and why they are important for engineering memory devices.
Researchers claimed that the ferroelectric capacitor built in their lab could survive 10 billion rewrite cycles, nearly 100,000 times more than what today’s flash can endure.
Unlike semiconductor-based devices, ferroelectric memory devices are not affected by external radiation. This means they could withstand cosmic ray exposure and even operate in outer space.