Water key to millions of gigabytes of memory in a cubic centimetre
11 May 2006
A computing principle popular in the 1960s, ferroelectricity, together
with a dose of water could provide extreme densities of computer memory. The
computer memory is so dense that a cubic centimeter contains 12.8 million
gigabytes (GB) of information. This is equivalent to an iPod playing music
for 100 millennia without repeating a single song or a USB thumb-drive with
room for 32.6 million full-length DVD movies.
Ferroelectric materials possess spontaneous and reversible electric
dipole moments. Until recently, it was technologically difficult to
stabilize ferroelectricity on the nano-scale. This was because the
traditional process of screening the charges was not completely effective.
However Jonathan Spanier from Drexel University and his research colleagues
have proposed a new and slightly unusual mechanism for stabilizing the
ferroelectricity in nano-scaled materials: surrounding the charged material
with fragments of water.
All ferroelectric materials, even Spanier’s wires that are 100,000 times
finer than a human hair, need to be screened to ensure their dipole moments
remain stable. Traditionally this was accomplished using metallic
electrodes, but Spanier and his team found that molecules such as hydroxyl
(OH) ions, which make up water, and organic molecules, such as carboxyl
(COOH), work even better than metal electrodes at stabilizing
ferroelectricity in nano-scaled materials, proving that sometimes water and
electricity do mix.
“It is astonishing to see that molecules enable a wire having a diameter
equivalent to fewer than ten atoms to act as a stable and switchable dipole
memory element,” said Spanier, an assistant professor of materials science
and engineering at Drexel.
If commercialized, ferroelectric memory of this sort could find its way
into home computers, rendering traditional hard-drives obsolete. The extreme
capacity offered by such a device could easily put a room full of
hard-drives and servers into a jacket pocket, but this idea can be applied
to other computer components, such as ferroelectric RAM.
RAM is necessary in a computer because it stores information for programs
that are currently running. As this news release was written, RAM stored the
words in a file. Because RAM can transfer files faster than a hard-drive, it
is used to handle running programs. However most RAM is volatile, and if the
computer loses power all the information in RAM is lost. This is not the
case with ferroelectric memory.
Ferroelectric memory is non-volatile, so it is entirely possible for
files to be stored permanently in a computer’s RAM. Applying nano-wires and
the new stabilization method to existing ferroelectric RAM would deal a
double blow to hard-drives in size and speed.
Spanier and his colleagues, Alexie Kolpak and Andrew Rappe of the
University of Pennsylvania and Hongkun Park of Harvard University, are
excited about their findings, but say significant challenges lie ahead,
including the need to develop ways to assemble the nanowires densely, and to
develop a scheme to efficiently write information to and read information
from the nanowires. In the interim, Spanier and his colleagues will continue
to investigate the role of molecules on ferroelectricity in nanowires and to
develop nano-scaled devices that exploit this new-found mechanism.