The team developed a new technique to capture atomic motions in a nanoscale switch. (Image Credit: SLAC National Accelerator Laboratory)


Researchers developed an extremely fast, new imaging technique that uses an electron diffraction camera to capture atoms' motion in a computer switch while it turns on and off. The results show a short-lived electronic state that could lead to faster and more energy-efficient computers. This newfound technique could also allow researchers to investigate electronic switching limitations.


The team from SLAC, Stanford University, Hewlett Packard Labs, Penn State University, and Purdue University observed devices made of vanadium dioxide due to the materials' ability to transition between insulating and electrically conducting states near room temperature. It also shows promise as a switch for future computing and brain-inspired computing since it generates electronic pulses that imitate the human brain's neural impulses.


The team applied short voltage pulses to turn the switches on and off while capturing snapshots of vanadium dioxide's atomic structure, which showed subtle changes over billionths of a second. Those voltage pulses' timing synced with the electron pulses generated by SLAC's ultrafast electron diffraction camera, MeV-UED. Afterward, the team put the MeV-UED's snapshots together to produce a molecular move of the atomic motions.


The team applied electrical pulses to transition the switch between insulating and conducting states. Afterward, they used the MeV-UED camera to capture snapshots of the material's atomic structure. (Image Credit: SLAC National Accelerator Laboratory)


"This ultrafast camera can actually look inside a material and take snapshots of how its atoms move in response to a sharp pulse of electrical excitation," said collaborator Aaron Lindenberg, an investigator with the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC and a professor in the Department of Materials Science and Engineering at Stanford University. "At the same time, it also measures how the electronic properties of that material change over time."


This camera led to the discovery of a new, intermediate electronic state within the vanadium dioxide, which is produced by applying fast electrical pulses to the material. The state emerges for a few microseconds while the materials transition from an insulating to conducting state. During its transition, the metastable phase's atomic structure remains unaffected. This is crucial due to the material's insulating and conducting states containing different atomic arrangements. Plus, it takes energy to switch from one state to another. As the transitions occur through the intermediate state, the switching process can perform without modifying the atomic arrangement.


When applying a voltage pulse, the material transitions from an electrically insulating to conducting state without modifying its atomic structure. (Image Credit: SLAC National Accelerator Laboratory)


The researchers also realized that the material's defects cause the intermediate state to become stabilized. Now, the team is studying ways to engineer these defects to provide the intermediate state with more stability and longevity. Doing so would allow them to develop devices that can perform electronic switching without atomic motion, allowing them to run faster while consuming less energy.


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



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