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at a time. Every electron is passing the same way, so the device is always stable.”
Yap’s team had made a transistor without a semiconductor. When sufficient voltage was applied, it switched to a conducting state. When the voltage was low or turned off, it reverted to its natural state as an insulator.
What’s more, there was no “leakage”. In other words, no electrons from the gold dots escaped into the insulating BNNTs, thus keeping the tunnelling channel cool. In contrast, silicon is subject to leakage, which wastes energy in electronic devices and generates a lot of heat.
Other people have made transistors that exploit quantum tunnelling, explains Michigan Tech physicist John Jaszczak, who has developed the theoretical framework for Yap’s experimental research. However, those tunnelling devices have only worked in conditions that would discourage the typical cellphone user.
Jaszczak says, “They only operate at liquid-helium temperatures”.
The secret to Yap’s gold-and-nanotube device is its submicroscopic size: one micron long and about 20 nanometres wide.
”The gold islands have to be on the order of nanometres across to control the electrons at room temperature,” Jaszczak says. “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 tunnelling channels can be miniaturised into virtually zero dimension when the distance between electrodes is reduced to a small fraction of a micron,” says Yap.
Yap has filed for a full international patent on the technology.
This work is described in the article “Room Temperature Tunneling Behavior of Boron Nitride Nanotubes Functionalized with Gold Quantum Dots,” by Chee Huei Lee et al, published online on June 17th in Advanced Materials. DOI: 10.1002/adma.201301339
This work was funded by the Office of Basic Energy Sciences of the US Department of Energy (Award # DE- FG02-06ER46294, PI:Y.K.Yap) and was conducted in part at ORNL (Projects CNMS2009-213 and CNMS2012- 083, PI: Y.K.Yap).
TGL4203-SM DC - 30 GHz wideband analogue attenuator
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www.compoundsemiconductor.net July 2013
TriQuint GaAs RF devices support NASA missions
Gallium arsenide MMICs have been used in the space pioneer’s Mars campaign
TriQuint Semiconductor reflected on its role in helping land NASA’s Curiosity rover safely on Mars as program managers say the mission is reaching an important turning point.
The firm has supported NASA programs for decades, including devices aboard the Sky Crane landing radar of the Mars Science Laboratory (MSL) and its Curiosity rover.
The MSL captured worldwide attention on August 6th, 2012 when its Sky Crane travelled the now-famous ‘seven minutes of terror’ to lower Curiosity safely to the Martian surface. NASA accomplished its feat with a pre- programmed landing sequence that was vital since the communication time delay between the planets meant Curiosity’s final descent could not be piloted from Earth.
TriQuint delivered four Sky Crane landing radar components that helped make a safe touchdown possible. The Sky Crane’s success culminated four year’s work by TriQuint engineers who consulted with NASA’s Jet Propulsion Laboratory (JPL).
Soon after landing, Curiosity confirmed that the Gale Crater site had once been capable of supporting microbial life. Since then it has found an ancient stream bed and allowed scientists to determine that the Martian radiation environment is similar to what astronauts experience aboard the International Space Station.
The rover collected rock samples containing sulphur, nitrogen, hydrogen, oxygen, phosphorus and carbon, leading scientists to believe Mars could have supported microbial life billions of years ago. The MSL is now nearly half way through its planned 23 month mission.
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