- The atomic-scale transistor made of a silver atom is approximately 1 nanometer in size.
- It consumes extremely low voltage of the order of 10 mV.
- This 3-terminal switch can work at room temperature – a big plus point for future applications.
For the last 5 decades, the number of transistors per silicon chip has doubled nearly every 18 months. In 2017, the transistors count in a commercial single-chip processor reached more than 18 billion.
However, the traditional silicon transistors can be scaled down to a certain limit only. We’ve now almost reached a phase where further reducing the size of transistors would affect its performance.
Scientists are now looking for new techniques to secure the new generation of microelectronics. Recently, physicists at the Karlsruhe Institute of Technology came up with single atom transistor, the world’s smallest transistor, that can switch electric current by repositioning a single atom.
It’s a completely new technical approach, in which transistors exclusively contains metal (no semiconductors). This enables the device to work at extremely low voltages.
How Small It Is And How Does It Work?
The size of the switching unit in a silver single-atom transistor is approximately 1 nanometer. This is much smaller than the gate length scaling limit (5 nanometers) in silicon transistors.
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The existing semiconductors require operation voltage as high as the order of 1000 mV. The silver-single atom transistors, on the other hand, consumes extremely low voltage of the order of 10 mV. This is much less than tunnel field-effect transistors, multigate transistors and germanium nano-devices that consumes nearly 0.5 V.
These single-atom transistors are 3-terminal resistance switches developed on the basis of metallic quantum point contacts. They are fabricated with one of the following three methods –
- Scanning tunneling microscope
- Mechanically controllable break junction
- Electrochemical procedures with both solid and aqueous electrolytes
In this work, researchers demonstrated atomic-scale silver quantum point contacts (in nearly 100 nanometers gaps) with high mechanical and thermal stabilities within an aqueous electrolyte, and utilized them as 3-terminal switches (transistors) controlled via an independent gate electrode.
Reference: Wiley Online Library | doi:10.1002/adma.201801225 | Karlsruhe Institute of Technology
Between two tiny metallic contacts, there is a small gap that can accommodate one metal atom. The researchers used an electric control pulse to adjust the position of this single atom of silver, and closed the circuit. This circuit is interrupted when the atom is removed again.
Is It Reliable?
Single Atom transistor | Credit: Thomas Schimmel/KIT
The transistor switches electric current due to the controlled reversible motion of an atom. Unlike quantum electronics instruments, it doesn’t only work at near absolute zero (-273°C), but also at room temperature, which is a big plus point for future applications.
The atomic-scale point contacts didn’t have any detects within the immediate contact region. Also, the integer quantum conductance characteristics of the transistors showed that silica gel in the electrolyte doesn’t affect the transportation of an electron in atomic-scale point contacts.
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Researchers also analyzed the viscosity of the quasi-solid-state electrolyte and found that it changed over a specific course of time. However, this change didn’t affect the switching behavior of the atomic-scale transistor.
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