Scientists have turned grains of salt into tiny electrical switches
A group of scientists from Liverpool University, University College London and University of Zaragoza, Spain, has found a new and rather unusual way to control the switching of electrical conductivity at the nanoscale level. A tiny electrical switch is a crystalline salt layer, including a common salt, several atoms thick. This flat crystal is located on a thin base of pure copper, separated from it by a layer of copper nitride. This entire multilayer structure is a so-called "electric dipole", the orientation of which can be changed by applying an external electric field.
If you take any of the most materials and turn it upside down, its crystal lattice will look exactly the same in both cases at the atomic level. Naturally, the movement of electric charges along such a material is completely independent of its spatial orientation and the direction of motion of the electric current. In some materials such symmetry is not observed, and the electric charges moving in them line up, forming electric dipoles, the orientation of which can be changed electrically. If the orientation of these dipoles is maintained after the removal of the field, then such materials are referred to ferroelectrics, electrical analogs of ferromagnets.
The property of preserving the direction of the magnetic magnetization of ferromagnets has been widely used for many years in magnetic recording and information storage devices. Unfortunately, the same wide application of ferroelectrics is prevented by the fact that these materials lose the ability to switch, being included in nanoscale electrical circuits.
To overcome this problem, scientists used the fact that the properties of some materials vary radically in the case of giving them a flat, conditionally two-dimensional shape, when the thickness of the material layer becomes equal to the thickness of several atomic layers. These unique properties, in this case, have a layer of copper nitride, a layer of salt, sodium chloride, and a layer of potassium bromide, which in some experiments was used to replace the salt layer.
As a result of acquiring new unique properties, the salt layer exhibits stable ferroelectric properties, allowing with a sufficiently high efficiency to control the movement of electric current through the multilayer device.
"By adding together the finest layers of different materials that are insulators originally, we can get a completely new electrical behavior of the device that is not peculiar to any of the materials individually," says Cyrus Hirjibehedin, the lead scientist of the project, "This approach will allow we significantly expand the rich assortment of conditionally two-dimensional structures on the basis of which it will be possible to create ultra-miniature electronics with very wide and unique functionality. "