Every day, modern society creates more than a billion gigabytes of new data. To store all this data, it is increasingly important that each single bit occupies as little space as possible.
Scientists at the Kavli Institute of Nanoscience at Delft University in the Netherlands managed to build a memory of one kilobyte (8,000 bits), where each bit is represented by the position of one single chlorine atom.
“In theory, this storage density would allow all books ever created by humans to be written on a single post stamp,” said lead scientist Sander Otte.
They reached a storage density of 500 Terabits per square inch (Tbpsi), 500 times better than the best commercial hard disk currently available.
In 1959, physicist Richard Feynman challenged his colleagues to engineer the world at the smallest possible scale.
In his famous lecture ‘There’s Plenty of Room at the Bottom’, he speculated that if we had a platform allowing us to arrange individual atoms in an exact orderly pattern, it would be possible to store one piece of information per atom.
To honour Feynman, researchers coded a section of his lecture on an area 100 nanometres wide.
The team used a scanning tunnelling microscope (STM), in which a sharp needle probes the atoms of a surface, one by one. With these probes scientists cannot only see the atoms but they can also use them to push the atoms around.
“Every bit consists of two positions on a surface of copper atoms, and one chlorine atom that we can slide back and forth between these two positions,” said Otte.
“If the chlorine atom is in the top position, there is a hole beneath it – we call this a one. If the hole is in the top position and the chlorine atom is therefore on the bottom, then the bit is a zero,” he said.
Since chlorine atoms are surrounded by other chlorine atoms, except near the holes, they keep each other in place.
This method with holes is much more stable than methods with loose atoms and more suitable for data storage, researchers said.
They organised their memory in blocks of 8 bytes (64 bits). Each block has a marker, made of the same type of ‘holes’ as the raster of chlorine atoms.
Inspired by the pixelated square barcodes (QR codes) often used to scan tickets for airplanes and concerts, these markers work like miniature QR codes that carry information about the precise location of the block on the copper layer.
The code will also indicate if a block is damaged due to some local contaminant or an error in the surface.
This allows the memory to be scaled up easily to very big sizes, even if the copper surface is not entirely perfect.
The research was published in the journal Nature Nanotechnology.