Silver sputtered nano chips mimic brain synapse

American researchers aiming to imitate the functionality of a cat's brain have developed an easily-fabricated, nanoscale device that emulates the connectivity between neurons in the brain.

The electronic device, known as a memristor ('memory' + 'resistor'), is analogous to a biological synapse in that its conductance can be precisely altered by controlling the charge running through it. The researchers found that changing the way they embedded silver ions in the silicon-based devices enhanced their performance.

A memristor's resistance is controlled by its 'memory' of the currents and voltages it has been exposed to. In the memristor, current flow is associated with ion motion, changing its resistance as they move. Previous memristors introduced silver ions to perform this function into the silicon from an electrode deposited on top. However, this process carves localised conduction channels responsible for the abrupt changes.

The researchers introduced silicon and silver simultaneously via co-sputtering. Using an argon plasma, they ejected atoms from pure elemental targets into a vacuum chamber containing the partially-fabricated memristors. The atoms deposit onto the device in a 20-30nm thick film, allowing easy control over the ratio between the two components.

Memristors can simulate synapses because electrical synaptic connections between two neurons can seemingly strengthen or weaken depending on when the neurons fire. The researchers demonstrated that their memristor performs an equivalent function with a conventional silicon-based circuit acting as neurons, increasing and decreasing the memristor's resistance.

This work is a huge stride towards the realisation of biology-inspired computing.