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World’s smallest storage device writes information atom by atom

STM scan (96 nm wide, 126 nm tall) of the 1 kB memory, written to a section of Feynman’s lecture, “There’s Plenty of Room at the Bottom” (credit: TU Delft/Ottelab)

Scientists at Kavli Institute of Nanoscience at Delft University have built a nanoscale data storage device containing 1 kilobyte (8,000 bits) with a storage density of 500 terabits per square inch (Tbpsi) — 500 times denser than the best commercial hard disk drive currently available. 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,” says lead scientist Sander Otte. The research is reported today (Monday July 18) in Nature Nanotechnology.

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.

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 honor the visionary Feynman, Otte and his team have coded a section of Feynman’s lecture on an area 100 nanometers wide.

“Sliding puzzle” scheme

Atomic data storage scheme (credit: Kavli Institute of Nanoscience)

The team used a scanning tunneling microscope (STM), in which a sharp needle probes the atoms of a surface, one by one. With these probes scientists can see atoms and push them around. “You could compare it  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. Which is why this method with holes is much more stable than methods with loose atoms and more suitable for data storage.

Kilobyte atomic memory. 1,016-byte atomic memory, written to a passage from Feynman’s lecture, “There’s plenty of room at the bottom.” The memory consists of 127 functional blocks and 17 broken blocks, resulting in an overall areal density of 0.778 bits per nm square. (credit: F. E. Kalff et al./Nature Nanotechnology)

The researchers 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 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 new approach offers excellent prospects in terms of stability and scalability. However, “in its current form the memory can operate only in very clean vacuum conditions and at liquid nitrogen temperature (77 K), so the actual storage of data on an atomic scale is still some way off.”

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


Delft University of Technology | Atomic scale data storage

Abstract of A kilobyte rewritable atomic memory

The advent of devices based on single dopants, such as the single-atom transistor, the single-spin magnetometer and the single-atom memory, has motivated the quest for strategies that permit the control of matter with atomic precision. Manipulation of individual atoms by low-temperature scanning tunnelling microscopy provides ways to store data in atoms, encoded either into their charge state, magnetization state or lattice position. A clear challenge now is the controlled integration of these individual functional atoms into extended, scalable atomic circuits. 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 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.

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Middle-age-plus memory decline may just be a matter of changing focus

When middle-aged and older adults were shown a series of faces, red regions of the brain were more active; these include an area in the medial prefrontal cortex that is associated with self-referential thinking. In young adults, by contrast, blue regions — which include areas important for memory and attention –+ were more active during this task. (credit: N. Rajah, McGill University)

Are you middle-aged or older and having problems remembering details, like where you left the keys or parked your car?

Cheer up, it may simply be the result of a change in what information your brain focuses on during memory formation and retrieval, rather than a decline in brain function, according to a study by McGill University researchers.

In the study, published in the journal, NeuroImage, 112 healthy adults ranging in age from 19 to 76 years were shown a series of faces. Participants were then asked to recall where a particular face appeared on the screen (left or right) and when it appeared (least or most recently). The researchers used functional MRI to analyze which parts of brain were activated during recall of these details.

Different parts of the brain involved

Senior author Natasha Rajah, Director of the Brain Imaging Centre, and colleagues found that young adults activated their visual cortex while successfully performing this task.

But for middle-aged and older adults, their medial prefrontal cortex was activated instead. That’s a part of the brain known to be involved with information having to do with one’s own life and introspection. This may reflect changes in what adults deem “important information” as they age, she said.

Rajah says middle-aged and older adults can improve their recall abilities by learning to focus on external rather than internal information, using mindfulness meditation, for example.*

Rajah is currently analyzing data from a similar study to discern if there are any gender differences in middle-aged brain function as it relates to memory. “At mid-life women are going through a lot of hormonal change. So we’re wondering how much of these results is driven by post-menopausal women.”

The research was supported by the Canadian Institutes of Health Research and by a grant from the Alzheimer’s Society of Canada.

* Other options to improve memory include:

  • Peppermint tea or rosemary essential oil, scientists at Northumbria University found in studies with subjects over age 65, presented at the British Psychological Society’s Annual Conference in Nottingham in April. Rosemary aroma significantly enhanced prospective memory (for things you plan to do).
  • Eight nutrients to protect the aging brain: cocoa flavanols, omega-3 fatty acids, phosphatidylserine and phosphatidic Acid, walnuts, citicoline, choline (found especially in eggs) and magnesium (avocado, soy beans, bananas and dark chocolate), and blueberries, according to a study published in the journal Food Technology. Details here.

Abstract of Changes in the modulation of brain activity during context encoding vs. context retrieval across the adult lifespan

Age-related deficits in context memory may arise from neural changes underlying both encoding and retrieval of context information. Although age-related functional changes in the brain regions supporting context memory begin at midlife, little is known about the functional changes with age that support context memory encoding and retrieval across the adult lifespan. We investigated how age-related functional changes support context memory across the adult lifespan by assessing linear changes with age during successful context encoding and retrieval. Using functional magnetic resonance imaging (fMRI), we compared young, middle-aged and older adults during both encoding and retrieval of spatial and temporal details of faces. Multivariate behavioral partial least squares (B-PLS) analysis of fMRI data identified a pattern of whole brain activity that correlated with a linear age term, and a pattern of whole brain activity that was associated with an age-by-memory phase (encoding vs. retrieval) interaction. Further investigation of this latter effect identified three main findings: 1) reduced phase-related modulation in bilateral fusiform gyrus, left superior/anterior frontal gyrus and right inferior frontal gyrus that started at midlife and continued to older age, 2) reduced phase-related modulation in bilateral inferior parietal lobule that occurred only in older age, and 3) changes in phase-related modulation in older but not younger adults in left middle frontal gyrus and bilateral parahippocampal gyrus that was indicative of age-related over-recruitment. We conclude that age-related reductions in context memory arise in midlife and are related to changes in perceptual recollection and changes in fronto-parietal retrieval monitoring.