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Massachusetts Institute of Technology - Storing data in individuals molecules

As explained in the news article entitled "IBM nano-technique - Scientists peer within Carbon nanotubes to see atomic structure in 3-D" - the Moore's Law is well-known for doubling of a computer chips' computational power - approximately every 18 months, which has had a similar mechanical engineering effect in the storage capacity of disk drives.

An international team of MIT researchers has devised an experimental technology dubbed 'molecular memory', which has the potential to store data in individual molecules - effectively promising a 1,000-fold increase in storage density.  However, previous such schemes have had to work on physical systems cooled to near absolute zero.  Excitingly on 23/01/2013 in an online edition of Nature - in an article entitled "Interface-engineered templates for molecular spin memory devices" - an international team of researchers led by Jagadeesh Moodera - senior research scientist in the MIT Department of Physics and at the MIT's Francis Bitter Magnet Laboratory - sought to describe a new molecular memory scheme, which worked at approximately the freezing point of water, which counts as Room Temperature (RT).

In addition, as previous schemes have required the 'sandwiching' of the storage molecules between two ferromagnetic electrodes, then the new MIT scheme would only require one ferromagnetic electrode.  Such simplification could greatly enhance its future manufacturing, as could the shape of the storage molecules themselves.  The scheme proposed by the MIT researchers consists of flat sheets of Carbon (C) atoms attached to Zinc (Zn) atoms, which can be deposited in very thin layers in extremely precise arrangements/patterns.   Please Note the storage molecules were developed by chemists at the Indian Institute of Science Education and Research in Kolkata - co-authors on the Nature paper.  In fact it is claimed by the Indian chemists that they believed the molecules could be useful for the type of experimental devices studied by Moodera's group, whereby the use of "spin" was seen to represent data.

Half a sandwich

Under Moodera's advice - Karthik Raman a former Ph.D student in MIT's Department of Materials Science and Engineering and now a scientist at IBM's Research Laboratory in India, and Alexander Kamerbeek, a visiting student from the University of Groningen sought to deposit a thin film of the material on a ferromagnetic electrode and added a second ferromagnetic electrode on top, which consequently is the standard structure for magnetic memories.  The principle idea is that a relative change in the electrodes' magnetic orientations enables for a sudden jump in the device's conductivity, whereby the two states of conductivity represent 1s and 0s in binary logic.  However, the MIT researchers surprisingly measured two jumps in conductivity, which would imply that the electrodes were changing the device's conductivity independently.

DCN Corp® - The new molecules are known as 'graphene fragments,' because they largely consist of flat sheets of carbon (C), which are attached to zinc (Zn) atoms. This makes them easier to align during deposition, which could simplify the manufacture of molecular memories.  Credit - Christine Daniloff, MIT, USA

To clarify such an observation the researchers performed the experiment again, but only used one ferromagnetic electrode and  one ordinary metal electrode.  The metal electrode purpose would be to read the current passing through the molecule, whereby they still recorded that the jump in conductivity still happened.  Therefore, as stated by Moodera - the capability to alter the molecules' conductivity with only one electrode could greatly simplify the manufacturing of future molecular memory.  Whereas traditional memory manufacturing has consisted of a bottom electrode of a memory cell, which is deposited in a perfectly flat layer and the subsequent storage molecules layered on top.  The next layer deposited being the top electrode, then the storage molecules will tend to mingle in between the storage molecules.  Unfortunately, if the electrode is magnetic, then such mingling can compromise the performance of the cell, but if the electrode is metallic then it will not.

In an alternative 'half a sandwich' design, then the top electrode is a tiny tip - positioned less than a nanometer (nm) above the storage molecules.  However, a magnetic electrode can still pose problems - in this case it is the limiting factor of how densely the storage cells can be coherently packed.

Stackable storage

It is claimed the shape of the molecules themselves could also simplify the manufacture of the molecular memory.  Typically, experimental molecular memories consist of 5-6 layers of molecules sandwiched between electrodes, and if such molecules are properly aligned they can contribute to large swings in conductivity.  However, the converse is also true  when the molecules are not properly aligned.  The 'ensuing' factor of proper alignment is an additional labor-intensive process.

Interestingly the molecules developed by the Indian researchers - consists of Zn atoms attached to flat sheets of C, and such elements tend to naturally align with each other.  In addition, the MIT researchers also demonstrated how the two layers of molecules were sufficient to produce a memory cell.  Raman stated "the switching effect near RT, is because of the strong interaction of the molecule with the magnetic surface", and "that makes the molecule magnetic as well as stabilising it."

Independently, Jing Shi, a professor of physics at the University of California at Riverside, points out that giant magneto-resistance - a physical phenomenon first discovered in 1988, and which forms the basis of most modern data-storage devices - could have been found in an alternative format by Moodera, Raman, and their colleagues.  Shi states "this is very novel, because they do not need very complicated material structures.", and as a consequence he continues to state "the fabrication process could be simpler and very flexible.  You only have to prepare this interfacial layer with the desired properties; then you can, in principle, recognise magneto-resistance."  In summary Shi comments that "obviously, it has some way to go", but it is at the Proof-of-Concept (PoC) stage.  Original article available here

DCN Corp finds the philosophy stated by the MIT researchers extremely interesting - especially when considering how many dip coats of homogeneous nano-fabrication could lead to the same 'half a sandwich' molecular switch, and all this accomplished at standard RT and atmospheric pressure.  To that point it has been long postulated that if a methodology can demonstrate reproducible/repeatable Surface Plasmon Resonance (SPR) signal feedback features, then the subsequent functionalisation could lead to a molecular switch, which only reacts upon inducement from the wavelength of a particular light/laser source.  Moving forward - if you or your colleagues are interested in making the above a reality - please ensure to contact the company as soon as practicably possible.