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Information storage at one atom per bit; a 1kB atomic memory

Information storage at one atom per bit; a 1kB atomic memory

Technology News |
By Graham Prophet



Specifically, the team created a 1 kByte memory array where each bit is represented by the (physical) position of one single chlorine atom. This equates to 500 Terabits per square inch (Tbpsi), 500 times better than the best commercial hard disk currently available. The team, led by the Institute’s Sander Otte, reported their work in Nature Nanotechnology on Monday July 18, 2016.

The work appears unlikely to lead to any practical memory in the near future; the researchers’ method of storing information relies on shifting positions of atoms, individually, using a scanning tunneling microscope. For some time it has been known that this tool can not only reveal surface detail at, literally, atomic scale, but it can also be used to manipulate individual atoms. Atoms can be “picked and placed” – transferred from the tip of the STM to a surface: or, as in this case, moved around on the surface. The read and write speeds of an atom-by-atom process using an STM are likely quite low, although the TU Delft team report that they have automated the read/write. And the process is stable at cryogenic temperatures – “up to”, the team notes, 77K (-216C). Nevertheless, it demonstrates that atomic-scale information is at least feasible, and the researchers make reference to the words of Richard Feynman over half a century ago.

 

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 the visionary Feynman, Otte and his team coded a section of Feynman’s lecture on an area 100 nanometres wide (The full scan here is 96 nm wide and 126 nm tall) of the 1 kB memory, as-annotated.

The method of pushing atoms around with the STM is compared by the team to a sliding puzzle. Otte explains; “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. If the chlorine atom is in the top position, there is a hole beneath it — we call this a 1. If the hole is in the top position and the chlorine atom is therefore on the bottom, then the bit is a 0.” Because the chlorine atoms are surrounded by other chlorine atoms, except near the holes, they keep each other in place. That is why this method with holes is much more stable than methods with loose atoms and more suitable for data storage. More formally, the substrate is an, “array of individual surface vacancies in a chlorine-terminated Cu(100) surface.”

 

The researchers from Delft organized 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, for instance due to some local contaminant or an error [lattice defect] 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 diagram shows the bit structure and the specific pattern employed to encode the letter ‘e’.

This research was made possible through support from the Netherlands Organisation for Scientific Research (NOW/FOM). Scientists of the International Iberian Nanotechnology Laboratory (INL) in Portugal performed calculations on the behaviour of the chlorine atoms.

 

For more information, please contact Dr. Sander Otte, Kavli Institute of Nanoscience, TU Delft: A.F.Otte@tudelft.nl, +31 15 278 8998

 

More at; https://ottelab.tudelft.nl

 

 

 

 

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