New memory stores light

Popular science magazine Nature is talking about a new prototype storage system that is faster than light and uses less power.

Ramamoorthy Ramesh, a materials scientist at the University of California, Berkeley, and Junling Wang, a specialist in oxide materials at the Nanyang Technological University in Singapore have emerged from their smoke filled labs with a storage device which combines speed, endurance and low power consumption by uniting electronic storage with a read-out based on the physics that powers solar panels.

The machine is based around bismuth ferrite which uses binary digits, or bits, as one of two polarisation states, and can switch between these states when a voltage is applied.

This Ferroelectric RAM has been around for a while but not found widespread use. One problem is that the electrical signal used to read out a bit erases it, so the data must be rewritten every time.

What Ramesh and Wang have done is use another property of bismuth ferrite to read these memory arrays in a nondestructive way.

Earlier research in 2009 demonstrated that bismuth ferrite has a photovoltaic response to visible light. So if you hit it with light a voltage is created Shining light on the material doesn’t change its polarization, and so does not erase the data stored in it.

Ramesh and Wang grew films of bismuth ferrite on top of a metal oxide, then etched it into four strips, created electrodes and uses these to polarize the cells, then shone light onto the whole array and found that it produced two types of voltage readings — one negative and one positive.

It took 10 nanoseconds to write to and read the cells, and recording the data requires about three volts. This is 10,000 times faster than flash which needs 15 volts to record.