According to Moores Law the
number of transistors on a integrated circuit doubles approximately every two
years (18 months). Gordron E. Moore described his law in this 1965 paper ‘Cramming more components onto integrated
circuits’ in the Electronics Magazine.
Because of this exponential growth over the last 48 years, this doubling has lead to 24 doublings of the orginal number of transitors that could be placed on a circuit board. Moore’s law is
starting to buckle, because transistors based on semiconductors can only get so
small.
"At the rate the current
technology is progressing, in 10 or 20 years, they won't be able to get any
smaller," said physicist Yoke Khin Yap of Michigan Technological
University. Not only is the current technology starting to reach the mature phase
of its growth (top of the S curve), but semiconductors also have another
disadvantage: they waste an exorbitant amount of energy in the form of heat.
Over the last few decades
scientist have experimented with different materials and molecule designs to continue
Moore’s Law of exponential growth. However, these scientists have
continued to experiment with semiconductor similar silicon. Dr. Yap wanted to try
something novel, something that might open the floodgates for a new age of
electronics.
"The idea was to make a
transistor using a nanoscale insulator with nanoscale metals on top," he
said. "In principle, you could get a piece of plastic and spread a handful
of metal powders on top to make the devices, if you do it right. But we were
trying to create it in nanoscale, so we chose a nanoscale insulator, boron
nitride nanotubes, or BNNTs for the substrate."
Yap’s research team had figured
out how to make a “virtual carpet” of BNNTS, which happen to be insulators
(that are highly resistant to electrical charge). By using a laser, the team
placed quantum dots (QDs) of gold as small as three nanometers across on top of
the BNNTs, forming QB-BNNTs.
When Yaps and Oak Ridge National Laboratory (ORNL) an
organization that Yap’s team collaborated with fired electrons through both ends of the QB-BNNTs at room
temperature. The electrons jumped with precision from gold dot to gold
dot. By a phenomenon known as quantum tunneling.
"Imagine that the nanotubes
are a river, with an electrode on each bank. Now imagine some very tiny
stepping stones across the river," said Yap. "The electrons hopped
between the gold stepping stones. The stones are so small, you can only get one
electron on the stone at a time. Every electron is passing the same way, so the
device is always stable."
Yap’s team had made a transistor
without using a semiconductor. When sufficient voltage was applied, it switched
to a conducting state, and when the voltage was low or turned off, it reverted
to its natural state as an insulator. During this process there was no leakage.
Meaning, no electrons from the gold dots escaped into the insulating BNNTs,
allowing the tunneling channel to remain at a cool temperature, while silicon
is subject to leakage, that waste energy and generates a lot of excess heat.
The method that separates Yap’s
success to others who have tried to exploit quantum tunneling is that Yaps
gold-and-nanotube device is its submicroscopic size: One micron long and about
20 nanometers wide. “The gold
islands have to be on the order of nanometers across to control the electrons
at room temperature," Jaszczak said. "If they are too big, too many
electrons can flow." In this case, smaller is truly better: "Working
with nanotubes and quantum dots gets you to the scale you want for electronic
devices."
"Theoretically, these
tunneling channels can be miniaturized into virtually zero dimension when the
distance between electrodes is reduced to a small fraction of a micron,"
said Yap.
FUTURE IMPLICATIONS
With Moore’s Law is coming to an
end in the next 10 to 20 years, a new technology must raise to take its place
to continue the technological development that has been seen in the last 50
years. In the future, we are going to see more scientists using quantum
phenomena to over come the traditional physical barriers that are starting to
loom and threaten technological development. Yap’s method could continue Moore’s law
along with creating more power efficient devices that could go days without
being charged.