Researchers Observe a New State In Electronic Switches
A research team created a new camera that was able to take snapshots of the movement of atoms inside tiny quantum switches.
The research team consists of researchers from the Department of Energy’s SLAC National Accelerator Laboratory, Penn State University, Purdue University, Stanford University, and Hewlett Packard Labs.
The material used in this research has been known to exist in two forms: the conducting state, which conducts electricity, and the insulating state, which does not. Under natural conditions, the two states have slightly different atomic arrangements and it takes energy to go from one to the other. The researchers found that when shocked electrically, these materials enter a transient conducting state in which they go from electrically insulating to conducting without changes to the atomic arrangement. Image courtesy of SLAC National Accelerator Laboratory.
Electronic devices contain millions of nano-switches. These switches are used to either conduct or interrupt currents. Due to their responses electronic devices can compute and store information. Electronic devices operation is defined by their speed and energy consumption. The switches’ efficiency has the most effect on these two terms. So to boost the speed of an electronic device, or minimize energy consumption, improving the switches’ efficiency is important.
The Experimental Components and Procedure
The researchers started by creating a camera that can visualize atomic motions that occur inside switches during their operation.
“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.”
The electronic devices used for testing were developed by the researchers. These electronic devices can be operated millions of times. The researchers used an ultrafast electron diffraction source to produce the short electron pulses and photograph the electronic structures. The final component is a synchronization scheme.
The switches are cycled on and off several times, in the meantime snapshots of the atomic structure are taken at different points of operation. The final result is a stroboscopic movie of the motion of the structures of the atoms. The time scale of the movie is a billionth of a second scale.
“This research is a breakthrough in ultrafast technology and science,” says SLAC scientist and collaborator Xijie Wang. “It marks the first time that researchers used ultrafast electron diffraction, which can detect tiny atomic movements in a material by scattering a powerful beam of electrons off a sample, to observe an electronic device as it operates.”
The Final Results
The known operation of a switch is turning from an insulating state to a conducting state and vice versa. The forms of atoms change when the switch turns from one state to another.
The electrical shocks used in the experiment show another state of operation where the switch changed from insulating to conducting but without a change in the atom positions. This state exists in only a millionth of a second.
“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.”
The future challenge is making the switch move from the insulating state to the new conducting state in a stable operation. If achieved this will make electronic switching possible without atomic motion, therefore, developing faster and more energy-efficient electronic devices.
The DOE Office Of Science funded this research.