As the modern-day society produces increasingly large amounts of data, researchers in the Netherlands have developed the world's smallest hard disk. Small as it is, the rewritable data-storage device can store 500 Terabits per square inch (Tbpsi), which is enough to store each of all the books written by humans.

The disk uses chlorine atoms to come up with the most efficient method of storing data yet devised. The disk's storage density of 500 Tbpsi is 500 times better compared with the most efficient disk that is currently available on the market.

The new technique that researchers employed involve using scanning tunneling microscope (STM) that uses a sharp needle to individually probe the atoms of a surface. The atoms represent binary code used for encoding data in computers.

Delft University of Technology experimental physicist Sander Otte, the lead author of the study that described the development of the storage device, compared the method to how sliding puzzles work.

Otte explained that every bit is comprised of two positions lying on copper atom surface and a chlorine atom that can be slid back and forth between the two positions, which represents either "one" or "zero."

The researchers said that since the chlorine atoms — excluding those near the holes — are surrounded by other chlorine atoms, they secure each other in place, which makes the set-up more stable than those that involve loose atoms making it more suitable for storing data.

Otte and colleagues organized memory into blocks of 8 bytes (64 bits), each of which was assigned a marker made from the same types of holes as those of the raster of chlorine atoms.

The markers serve as miniature barcodes that carry information about the location of their block on the copper layer and can indicate when a block is damaged. This means that memory can be scaled up to a bigger size regardless of physical deficiencies in the copper surface.

"Here, we present a robust digital atomic-scale memory of up to 1 kilobyte (8,000 bits) using an array of individual surface vacancies in a chlorine-terminated Cu(100) surface," the researchers wrote.

"The memory can be read and rewritten automatically by means of atomic-scale markers and offers an areal density of 502 terabits per square inch, outperforming state-of-the-art hard disk drives by three orders of magnitude. Furthermore, the chlorine vacancies are found to be stable at temperatures up to 77 K, offering the potential for expanding large-scale atomic assembly towards ambient conditions."

The study is published in the journal Nature Nanotechnology on July 18.

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