The researchers used chemical vapour deposition to traverse a 2 to 3 nm diameter carbon nanotube across a silica substrate engraved with a trench to allow a portion of the carbon tube to span. Above the groove, palladium is added as the source and the drain. Under single carrier transmission conditions (ie, the gate voltage is less than -3.1 volts, hole transport is induced, and the gate voltage is greater than -2.1 volts. Electron transmission), the carbon nanotubes are emitted by the substrate and the junction formed by the suspended portion, and the luminous efficiency is about 107 photons per square nanometer per second when the current is 3 μA, which is larger than the current area. The LED is 105 times higher.
Researchers believe that the reason why carbon nanotubes emit light is that near the junction between the carbon nanotubes and the suspended portion, the energy band of the carbon tube will bend, and the generated electric field will accelerate the carrier and generate excitons. Binding pairs of electrons and holes); when electron-hole pairs recombine, they illuminate. According to the calculations of the researchers, the efficiency of this excitation method is more than 1000 times the efficiency of recombination of electrons and holes injected from both ends.
This study demonstrates that in low-dimensional nanostructures, electrons and holes have a very strong attraction, while the coupling between carriers and atomic vibrations is weak, and it is also the first time to prove that in a one-dimensional system, molecules Impact excitation of internal hot carriers (high energy carriers).
Since the carbon nanotube emits infrared light having a wavelength of 1-2 μm, it has the potential to be applied to optical communication, and the wavelength of the light can be adjusted by changing the diameter of the carbon tube. In addition, in the future, these carbon nanotube illuminators can be integrated on the same chip as electronic components such as carbon tubes or silicon, becoming new electronic or optoelectronic components.
Researchers at IBM and Duke University in the United States have recently succeeded in making single-walled carbon nanotubes emit high-intensity infrared light. They let a part of the carbon nanotubes hang over the silica substrate and, under unipolar operation, result in high-intensity infrared light from the junction of the carbon tube and the junction formed by the support.