Tungsten diselenide (WSe2), which belongs to a class of 2-D crystals known as transition metal dichalcogenides, is proving to be an attractive platform for producing solid-state quantum dots for emitting light.
While graphene has become increasingly used for optoelectronic applications, researchers at the University of Rochester claim that the work they have done with tungsten diselenide represents the first time that 2-D materials have produced optically active quantum dots.
The researchers believe that this research, details of which were published in the journal Nature Nanotechnology, could serve as a basis for integrating quantum photonics with solid-state electronics. The result could be a new way to produce so-called integrated photonics.
In the research, the Rochester team laid atomically thin sheets of the semiconductor tungsten diselenide one on top of the next, creating defects in the semiconducting material. These defects are what create the quantum dots: nanoscale semiconductor crystals that are sometimes described as “artificial atoms” because, like atoms, when they absorb the right amount of energy they subsequently give off energy as colored light.
The researchers discovered that the quantum dots they created by engineering the tungsten diselenide defects did not impact the electrical or optical performance of the semiconductor. Further, they found that they could control the electrical and optical properties of the quantum dots by applying either an electrical or magnetic field.
In this way, the researchers were able to control the brightness of the quantum dot’s light emissions simply by applying a voltage. In future iterations of the technology, the researchers believe they will also be able to tune the color of the emitted photons using a voltage, which will open up these quantum dots to applications including nanophotonic devices.
Another possibility opened up by the quantum dots having been produced in this way is a potential use in “spintronics,” where the spin of an electron is used to encode information rather than a charge.
"What makes tungsten diselenide extremely versatile is that the color of the single photons emitted by the quantum dots is correlated with the quantum dot spin," said Chitraleema Chakraborty, one of the authors of the Nature Nanotechnology paper, in a press release.
The researchers believe that the easy interaction between the spin and the photons should make them attractive for quantum information applications.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.