The golden path towards new two-dimensional semiconductors

Two-dimensional (2-D) semiconductors are promising for quantum computing and future electronics. Now, researchers can boron nitride nanotubes.

Gold is a conductive material already widely used as interconnects in electronic devices. As electronics have gotten smaller and more powerful, the semiconducting materials involved have also shrunk. However, computers have gotten about to small as they can with existing designs-to break the barrier, researchers have found quantum computing in the physics of quantum computation and the unusual behaviors of gold in quantum mechanics.

Researchers can convert gold into semiconducting quantum dots made of a single layer of atoms. Their energy gap, or bandgap, is formed by the quantum confinement-a quantum effect when the materials are so small. These 2-D gold quantum dots can be used with a bandgap that is tunable atom-by-atom.

Making the dots with monolayer of atoms is tricky and the bigger challenge is customizing their properties. When laid out on boron nitride nanotubes, researchers from Michigan Technological University have found that they can get gold quantum dots to the near-impossible. The mechanisms behind the gold dots to clump atom-by-atom is the focus of their new paper, recently published ACS Nano.

Yoke Khin Yap, professor of physics at Michigan Tech, led the study. He explains that the behavior of his team observed-atomic-level manipulation of gold quantum dots-can be seen with a scanning electron microscope transmission (STEM). The STEM's high-powered beam of electrons enables researchers to interact with the surface of boron nitride nanotubes. Basically, the gold atoms glide along the surface of the nanotubes and, they stabilize in a hover just above the hexagon honeycomb of the boron nitride nanotubes.

The atomic skiing and stopping is related to the so-called energy selective deposition. In the lab, the team takes an array of boron nitride nanotubes and runs a gold-laden mist past it; the gold atoms in the mist or nanoparticles nanoparticles, but some of the more energetic ones glide along the circumference of the nanotube and stabilize, then start to clump into monolayers of gold quantum dots. The team shows that gold is preferentially behind other gold particles that have stabilized.

"The surface of boron nitride nanotubes are atomically smooth, there are no defects on the surface, it is a neatly arranged honeycomb," Yap said, adding that the nanotubes are chemically inert and there is no physical bond between the nanotubes and gold atoms. "It's much like skiing: You can not ski on a bumpy and sticky hill with no snow, the ideal surface of the nanotubes is like fresh powder."

The search for new materials for future electronics and quantum computing Yap hopes that by demonstrating the effectiveness of gold, other researchers will be inspired to pay attention to other metal monolayers at the molecular-scale.

"This is a dream nanotechnology," Yap said. "It is a molecular-scale technology tunable by atom with an ideal bandgap in the visible light spectra." There is a lot of promise in electronic and optical devices.

The team's next steps include further characterization and incorporating device manufacturing to demonstrate all-metal electronics. Potentially, monolayers of metal atoms could make up the whole of future electronics, which would save a lot of manufacturing energy and materials.