Researchers from the Hebrew University succeeded in developing a transistor consisting of a single atom - the smallest and most stable

Israeli researchers have succeeded in producing a transistor based on one atom, in an electrical device that is only two nanometers long. Prof. Hadar Steinberg, one of the leaders of the research: "In our device, it is a transistor built with one atom that is only one nanometer from the conductors in its environment. We have reached a new limit in miniaturization capabilities"

In 2012, it was reported in the journal Nature Nanotechnology that Australian and American physicists succeeded in developing the world's smallest silicon transistor, consisting of a single atom of phosphorus inside a silicon wafer. The development was another step in the ongoing efforts to miniaturize transistors, which are a very basic and vital component in the electronics industry. The researchers stated that they used a scanning tunneling microscope (with which surfaces can be examined at the atomic level) to place the single phosphorus atom on a silicon plate, between electrodes, and saw that an electric current was generated. Until then, transistors based on a single atom had only been produced by chance, while the 2012 study was the first time this was done by design. In May of this year, it was researchers from the American Institute of Technology NIST and their colleagues from the University of Maryland, who worked on a similar experiment regarding which it was stated in Science Daily that "this is the second team in the world to succeed in building a single atom transistor".

The silicon transistor is an electronic switch or valve that makes it possible to implement logic devices that have been the mainstay of the information revolution since the 60s. The transistor is an electrical switch made of a semiconductor material, which forms the binary basis for electronic devices. The switch defines the binary digits 0 and 1 by two levels of voltage - high voltage and low voltage. These devices, as we know, are getting smaller and smaller, and in recent years have reached dimensions of up to about 10 nanometers. These dimensions make it possible to cram hundreds of millions of devices onto a single chip, and bring into the palm of everyone's hand a computing power that was considered imaginary in previous generations. Beyond that, transistors made up of single atoms are expected to be the building blocks of a new generation of quantum computers, with unparalleled memory and processing power. Why is it so important today to add and minimize the transistors? The smaller the transistor, the faster information control can be realized, and more devices can be packed into a given volume.

"In past studies, physicists were able to realize electronics on the basis of a single atom, but it is an atom that is on the surface. Over the years, researchers have not solved the main problem - the atom is on the surface, and therefore vulnerable to its environment," explains Prof. Hadar Steinberg, who these days is working together with researchers from the Rakeh Institute of Physics at the Hebrew University of Jerusalem on a transistor built from one atom, which has been reduced to the smallest known size to science. "Different from the previous studies, in our study, in the new system we created with a transistor built from one atom, electrical conduction is made possible through a defect embedded in an insulator. This system is very stable and less vulnerable. It is very important to emphasize that our goal is not who will reach a working transistor from one atom first, but also to contribute and innovate to science, to reach capabilities that did not exist before. In our device, it is a transistor built of one atom that is only one nanometer from the conductors in its environment."

And so, in a recent experiment led by Prof. Hadar Steinberg and with the assistance of doctoral student Itai Keren - both from the Rakah Institute of Physics at the Hebrew University of Jerusalem, published these days in the journal Nature Communications, the researchers were able to realize a transistor built with a single atom by using an electrode from the thinnest electrical conductor known to science - a material called graphene. Graphene is a single layer of graphite, which is a configuration of pure carbon, built in a layered structure. Each graphene layer is a sheet of carbon atoms with a honeycomb structure. Graphene has two key properties that allow it to realize electronics of single atoms. On the one hand, it is an excellent electrical conductor. On the other hand, as a result of its minimal thickness, it allows the passage of an electric field. Thus, unlike in a metal layer, an electric voltage applied to one side of a graphene sheet will "seep" to the other side.

The researchers used a method based on building devices from layered materials. This method is currently used by various research laboratories in the world, and it allows peeling off a layered material to the thickness of a single atom, and placing several layers on top of each other - as one would assume, for example a stack of paper or cards. The researchers built an electrical device at the heart of which was a very thin layer, only two nanometers thick, of a layered insulating material. On one side of the insulator they placed graphite, and on the other - graphene. In an electrical measurement, they discovered that the current leaves the graphite, skips through a single atom in the insulating layer, and reaches the graphene. By applying an electrical voltage to the other side of the graphene, the researchers were able to turn the current on and off, showing that the current was carried by a single atom. "Because of the use of graphene, it is possible to activate an electric field through the electrode, and not parallel to it. This is how we reach a new limit in miniaturization capabilities," explains Prof. Steinberg.

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More of the topic in Hayadan:

• Nanoscale wiring is the key to the future of transistors and electronics
• Molecular spintronics - a new technology for quantum computing
• "There is still a need to investigate how error correction can be performed before a universal quantum computer can be built"