One Atom Bit

Utilizing Scanning Tunnelling Microscope

A Quantum Sensor Made from Individual Iron Atoms

QNS researchers, in collaboration with a team of IBM researchers in the USA have succeeded in using individual iron atoms as quantum sensors. Using this sensor, they were able to measure the small magnetic field created by neighboring magnetic atoms, an effect that was previously not measurable in scanning tunneling microscopy.
This work is the first application of a recent breakthrough invention of the same team, which demonstrated electron spin resonance – a quantum mechanical measurement of single spins – in the STM. “We believe that this quantum sensor can be used to measure the spins in complex molecules with atomic-scale spatial resolution, sort of like a nano-GPS”, suggests Taeyoung Choi, first author of the recent study.

Scanning Tunneling Microscope

The Scanning Tunneling Microscope is a conceptually rather simple tool that has amazing capabilities. It ‘images’ the surface of a material – here labelled as sample – by bringing a really sharp metal needle – here labelled as tip – very close. The actual distance between the last atom on the tip and the atoms on the surface of the sample is about one nanometer, which corresponds to only about 4 atom spacings in most solid materials. At this close approach, electrons can jump from tip to sample and from sample to tip by using the quantum mechanical effect called tunneling. When a small voltage is applied between tip and sample, a current flows, which we measure. This current is extremely sensitive to the distance: for example it become 10 times smaller when the distance is increased from 1 to 1.1nm.

At QNS, we are using STM not only to image surfaces with atomic resolution but also to move the atoms into desired configurations. This enable us to engineer these nanostructures and then build them with ultimate precision. Finally, we use very high resolution spectroscopic measurements to investigate the electronic and magnetic properties of such systems.