Nanoscale method improves materials for advanced memory storage

Next-generation technologies, such as advanced memory storage solutions and brain-inspired neuromorphic computing systems, could touch almost every aspect of our lives, from the gadgets we use every day to solutions to major global challenges . These advances rely on specialized materials, including ferroelectrics, materials with switchable electrical properties that improve performance and energy efficiency.

A research team led by scientists at the Department of Energy’s Oak Ridge National Laboratory has developed a new technique for creating precise atomic arrangements in ferroelectrics, establishing a solid framework for advancing powerful new technologies. The article is published in the journal Nature Nanotechnology.

“Local modification of the atoms and electric dipoles that form these materials is crucial for new information storage, alternative computational methodologies or devices that convert high-frequency signals,” said ORNL researcher Marti Checa. principal of the project. “Our approach promotes innovations by facilitating the on-demand rearrangement of atomic orientations into specific configurations known as topological polarization structures that might not occur naturally.”

In this context, polarization refers to the orientation of small internal permanent electric fields in the material, called ferroelectric dipoles.

To create complex structures that can be activated as needed, the team’s technique uses an electric stylus that works like an ultrathin pencil. The stylus can effortlessly modify the ferroelectrics’ electrical dipoles by pointing them in selected directions, much like how children create images on magnetic drawing boards.

Just as the layout of a city shapes the way people move through it, designed topological structures impart distinctive properties to materials. The stylus presents exciting opportunities to create materials with tailored features, ideal for low-power nanoelectronics and high-speed broadband communications essential in the 6G era.

The transition from 5G to the sixth generation of mobile communications technology will involve significant advancements and transformations in the design and use of communications networks. Broadband and computing technologies are closely linked, each enhancing the performance of the other. Innovative materials will therefore play a crucial role in expanding computing possibilities.

Upcoming Nanoelectronic Advances

Today’s conventional computers communicate in a simple language consisting of “yes” and “no”, represented by ones and zeros. This binary system relies on the flow of electricity through tiny circuits. However, this dual-choice framework is limiting and power-intensive due to data writing and reading requirements.

In contrast, topological polarization structures can quickly and efficiently change their polarization states, providing high stability with low power consumption for switching. This rapid change in polarization increases the value of ferroelectrics, improving the speed, efficiency, and versatility of various devices. Additionally, they enable data retention without power, paving the way for the development of high-density, energy-efficient computing systems.

Scientists are investigating materials that can process information faster, as required for high-speed communications in the 6G era. These structures can also be exploited in devices operating at high frequencies, thanks to intrinsic sub-terahertz resonances, which are natural oscillations or vibrations within a material or system that occur at frequencies below a terahertz, or one trillion hertz.

Such advances could significantly improve the processing power and efficiency of future computing systems, allowing them to solve more complex problems and perform tasks with greater adaptability and speed – capabilities that classical computers must have. hard to reach.

Finally, these structures allow precise control of electronic and optical properties and could therefore be used for tunable optoelectronic devices. A combination of unique electrical, mechanical, and thermal properties make ferroelectrics ideally suited for neuromorphic computing and other new technologies.

Rapid polarization changes, superdomain dynamics

ORNL-led research has unveiled how an advanced ferroelectric ceramic material, commonly known as PSTO, changes its polarization during a multi-step process, guided by the electric stylus. PSTO, or lead strontium titanate, is essentially composed of lead, strontium, titanium and oxygen.

A concept called leakage field is commonly used to explain why ferroelectrics reorient their tiny electric dipoles (small positive and negative charges) in the plane of the material in response to an electric field moving along the surface.

However, the research team proposed as an alternative the existence of an intermediate out-of-plane state to describe the phase that occurs when the material transitions from one polarization state to another. This phase is a brief change in polarization direction that occurs when the vertical portion of an electric field momentarily orients the electric dipoles out of the plane of the surface as the polarization changes in a thin layer of ferroelectric material.

Scientists’ knowledge of the out-of-plane intermediate state has enabled the precise, on-demand manipulation of superdomain structures. Superdomain structures are large-scale models of tiny regions within ferroelectric materials such as PSTO, each with a different alignment of electric dipoles. Superdomain structures are important because they affect the performance of materials in various applications by influencing their overall behavior and properties.

This study also demonstrated the ability to examine the delicate balance between elastic and electrostatic energy. Ferroelectrics have both mechanical (elastic) and electrical (electrostatic) energy interactions, which influence each other. For example, changing the shape of a ferroelectric can affect its electrical properties, and vice versa. Studying this balance helps researchers understand how to more precisely control the material’s behavior.

Additionally, the researchers explored the accommodation of frustrated boundaries, that is, areas where different regions with different electrical properties meet in the material. These boundaries cannot easily align or adjust to minimize energy expenditure due to conflicting forces or constraints and therefore rarely occur in nature. However, creating new topological polarization structures on demand allows researchers to stabilize these frustrated superboundaries and study their unique properties.

Prediction, control with nanoscale precision

By integrating structural and functional data about the ferroelectric material collected through correlative microscopy techniques, the researchers created detailed phase field models that predict the material’s behavior under various conditions. This capability facilitates the understanding and optimization of material stability and polarization.

“Our project developed advanced methods to accurately model materials at the nanoscale,” Checa said.

“By combining specially designed electric stylus tip movements with automated experimental setups, we have demonstrated our ability to explore new and complex states of ferroelectric materials that were not previously accessible. A key aspect of this achievement is that it allows a better understanding and control of the unique properties of these materials.