Atomic Storage Devices: The Next Answer to the Growing Demand for Bigger Storage Capacity
Image Source: Extreme Tech
Year after year the demand for bigger storage capacity increases. Currently Seagate has the SSD with the largest capacity, up to 60TB, available commercially(that’s if you can afford the USD $10,000 price tag). But this might soon be not enough, or at least, be the minimum requirement. As technology grows, the size of data people use and keep grows as well. Say, for example, a photographer who works using digital cameras. The better the camera, the better the quality of image captured, the bigger the size of the image file. Or how about movies? The better the quality of a movie file the bigger the filesize is. Just compare the files in VCDs years ago to those HD movies you download with BitTorrent.
So it really isn’t surprising that mankind would eventually turn to smaller things to be able to pack in more data in a smaller space, a prediction known as Moore’s Law. Just last year, BBC reports of an article in Nature Nanotechnology journal reports of using the positions of individual chlorine atoms on a copper surface to store to store information. Titled “A kilobyte rewritable atomic memory“, it tells Dutch scientists were able to develop a rewritable memory using this method. The team responsible is led by a Sander Otte, at the Technical University of Delft (TU Delft). With each bit of data represented by the position of a single chlorine atom, his team was able to reach a density of 500 Terabits per square inch. According to him, in theory, this storage density would allow all books written in history to be stored into something the size of a post stamp. They used a scanning tunneling microscope (STM), in which a sharp needle probes the atoms on the surface one by one. This allowed them to push the atoms around, which Dr. Otte compares to a sliding puzzle.
Image Source: BBC
“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,” he said. “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.”
His team believe their method is much more stable than methods using loose atoms, and more suitable for practical data storage applications, because the chlorine atoms are kept each other in place, surrounded by other chlorine atoms (except near the holes).
Though the method is far from perfect and his team believes that it isn’t ready yet: stable information storage could only be demonstrated at a temperature of 77 Kelvin (-196C) and the speed of single write and read processes is still slow – on the scale of minutes.
Another study in atomic storage was published just this month. Last March 9 a similar study is published in Science Daily titled “Single atom memory: The world’s smallest storage medium” quoting that “one bit of digital information can now be successfully stored in an individual atom.” Andreas Heinrich, current Director of the Center for Quantum Nanoscience, within the Institute of Basic Science (IBS, South Korea), led the research effort that made this discovery at IBM Almaden Research Center (USA).
Image source: Science Daily
Using an STM, this time they use a special tip to apply an electric pulse to to change the direction of magnetization of individual holmium atoms. By doing that, they could write a memory of either 1 or 0 in a single holmium atom as well as swap the two.
Then a quantum sensor designed by Heinrich’s team was used to read the memory stored in the holmium atom. It consists of an iron atom placed next to the holmium atom. Using this technique, as well as another one called tunnel magnetoresistance, the researchers could observe that holmium maintains the same magnetic state stably over several hours.
Another finding they had is that by placing holmium atoms even one nanometer apart did not impact their ability to store information individually. It was expected that the magnetic field from one atom would impact its neighbor. In this way, the scientists could build a two bit device with four possible types of memory: 1-1, 0-0, 1-0 and 0-1 clearly distinguished by their iron sensor.
“Heinrich is one of the few in the world using this tool to measure and change the properties of individual atoms. He plans to significantly expand on this research at his newly created IBS research center, located at Ewha Womans University in Seoul.” according to Science Daily.