At the center of modern technology lies the logic circuitry provided by semiconductor devices. Extending circuit logic to the realm of nanotechnology requires the construction of atomic-scale systems, which has proven challenging. Both the electric nature of individual atoms and the need to place them at specific points within a crystal lattice has kept scientists from creating atom-scale transistors until the present.
Now, a group of researchers has fabricated a single-atom transistor by introducing one phosphorous atom into a silicon lattice. Through the use of a scanning tunnelling microscope (STM) and hydrogen-resist lithography, Martin Fuechsle et al. placed the phosphorous atom precisely between very thin silicon leads, allowing them to measure its electrical behavior. The results show clearly that we can read both the quantum transitions within the phosphorous atom and its transistor behavior. No smaller solid-state devices are possible, so systems of this type reveal the limit of Moore’s law—the prediction about the miniaturization of technology—while pointing toward solid-state quantum computing devices.
from Ars Technica