Scientists take first snapshots of ultra-fast switching in quantum electronic device

The electronic circuits that calculate and store information contain millions of tiny switches that control the flow of electric current. A better understanding of how these tiny switches work could help researchers push the boundaries of modern computing.

Scientists have now taken the first snapshots of atoms moving inside one of these switches when it turns on and off. Among other things, they discovered a short-lived state in the switch that could one day be exploited for faster, more power-efficient computing devices.

The SLAC National Accelerator Laboratory research team at the Department of Energy, Stanford University, Hewlett Packard Labs, Penn State University and Purdue University described their work in an article published in Science today.

“This research is a breakthrough in ultra-fast science and technology,” said Xijie Wang, scientist and SLAC collaborator. “This is the first time that researchers have used ultrafast electron diffraction, which can detect tiny atomic movements in a material by scattering a powerful beam of electrons on a sample, to observe an electronic device as it works . “

Enter the cycle

For this experiment, the team custom designed miniature electronic switches made from vanadium dioxide, a prototypical quantum material whose ability to go from an insulating state to an electrically conductive state near room temperature could be harnessed as a switch. for future calculation. The material also has applications in brain-inspired computing due to its ability to create electronic impulses that mimic neural impulses triggered in the human brain.

The researchers used electrical pulses to toggle these switches between insulating and conducting states while taking snapshots that showed subtle changes in the arrangement of their atoms in billionths of a second. These snapshots, taken with SLAC’s ultra-fast electron diffraction camera, MeV-UED, were chained to create a molecular film of atomic movements.

“This ultra-fast camera can actually look inside a material and take snapshots of how its atoms move in response to a pulse of electrical excitation,” said collaborator Aaron Lindenberg, a researcher at the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC. and professor in the Department of Materials Science and Engineering at Stanford University. “At the same time, it also measures how the electronic properties of this material change over time.”

With this camera, the team discovered a new intermediate state within the material. It is created when the material responds to an electrical impulse by changing from an insulating state to a conductive state.

“Insulating and conducting states have slightly different atomic arrangements, and it usually takes energy to switch between them,” said Xiaozhe Shen, scientist and SLAC collaborator. “But when the transition takes place through this intermediate state, the change can take place without any change in the atomic arrangement.”

Open a window on atomic movement

Although the intermediate state only exists for a few millionths of a second, it is stabilized by defects in the material.

As a follow-up to this research, the team is studying how to design these defects in materials to make this new state more stable and more durable. This will allow them to manufacture devices in which electronic switching can occur without any atomic movement, which would run faster and require less power.

“The results demonstrate the robustness of electrical switching over millions of cycles and identify possible limits to the switching speeds of such devices,” said collaborator Shriram Ramanathan, professor at Purdue. “The research provides invaluable data on the microscopic phenomena that occur during device operations, which is crucial for the design of circuit models in the future.”

The research also offers a new way to synthesize materials that don’t exist under natural conditions, allowing scientists to observe them at lightning-fast time scales, and then potentially adjust their properties.

“This method gives us a new way of looking at devices as they work, opening a window to see how atoms move,” said lead author and SIMES researcher Aditya Sood. “It’s exciting to bring together ideas from the traditionally distinct fields of electrical engineering and high-speed science. Our approach will enable the creation of next-generation electronic devices capable of meeting the world’s growing needs for intelligent and data-intensive computing.