Manufacturing the thinnest freestanding films with ferroelectric properties opens the door to smaller, more efficient devices

April 20, 2023

(Nanowerk News) Researchers at the Institute of Future Materials and Systems at Nagoya University in Japan have successfully synthesized barium titanate (BaTiO3) nanosheet with a thickness of 1.8 nanometers, the thinnest thickness ever made for a freestanding film. Since thickness is tied to functionality, their findings open the door to smaller, more efficient devices. This research is published in the journal Advanced Electronic Materials (“Molecularly Thin BaTiO3 Nanosheet with Stable Ferroelectric Response”).

The development of increasingly thinner materials with new electronic functions is a highly competitive research area. Such devices are especially important in ferroelectrics, materials whose polarization can be reversed by an electric field. The ability to reverse polarization makes this material useful in memory and vibrational power generation.

However, as the materials used in these devices became smaller, they exhibited unpredictable properties that made their industrial use difficult. The big problem is the “size effect”, as when the thickness of a material is reduced to a few nanometers, its ferroelectric properties are lost.

Now, a team from the Department of Materials Chemistry of Nagoya University and the Institute of Materials and Systems for Sustainability (IMASS), led by Professor Minoru Osada (he), has successfully synthesized a defect-free BaTiO3 nanosheets with ferroelectric properties at a thickness of 1.8 nm using the aqueous solution process. The result is the thinnest free-standing film ever made. Despite being thin, these films exhibit ferroelectric properties, representing an important breakthrough in the manufacture of ferroelectrically active thin films. Manufacturing the thinnest freestanding films with ferroelectric properties opens the door to smaller, more efficient devices. (Image: Dr. Minoru Asada)

“However, for BaTiO3, a typical ferroelectric material, it is difficult to synthesize nanosheets by conventional synthetic methods. Therefore, it is necessary to develop new synthetic methods,” said Osada. “Generally the synthesis of BaTiO3 requires a calcination process that requires a temperature of 1000 °C or higher. Instead, we synthesized BaTiO3 nanosheets at a low temperature of 60°C using our process. Since the film thickness can be controlled using this method by varying the reaction time, the synthesis of nanosheets with two to six lattices is achieved.”

“If nanosheets with a thickness of several nanometers can be synthesized in ferroelectrics, new properties and applications are expected to be discovered. Our findings should provide important techniques for miniaturization of devices such as memory and capacitors.” “As existing technologies have reached their limits in both materials and processes, engineering like ours is essential. They offer dramatic improvements in performance and technological innovation through new materials and processes.”

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