The golden path towards new two-dimensional semiconductors.

2D gold quantum dots are atomically tuneable with nanotubes

Two-dimensional (2D) semiconductors are promising for quantum computing and future electronics. Now, researchers can convert metallic gold into semiconductor and customize the material atom by atom in boron nitride nanotubes. Credit: Bill Tembreull / Michigan Tech

Two-dimensional (2-D) semiconductors are promising for quantum computing and the electronics of the future. Now, researchers can convert metallic gold into semiconductor and customize the material atom by atom in boron nitride nanotubes.

Gold is a conductive material already widely used as interconnections in electronic devices. As the electronics have become smaller and more powerful, the semiconductor materials involved have also been reduced. However, computers have become as small as they can with existing designs: to break the barrier, researchers immerse themselves in the underlying physics of quantum computing and the unusual behaviors of gold in quantum mechanics.

Researchers can convert gold into semiconductor quantum dots made from a single layer of atoms. Its energy gap, or band gap, is formed by quantum confinement, a quantum effect when materials behave like atoms as their sizes approach the molecular scale. These 2-D gold quantum dots can be used for electronics with a band range that is tuneable atom by atom.

Making the points with a monolayer of atoms is complicated and the biggest challenge is to customize their properties. When they are placed in boron nitride nanotubes, researchers at Michigan Technological University have discovered that they can obtain gold quantum dots to make the near impossible. The mechanisms behind getting gold points to cluster atom by atom is the focus of his new document, recently published in ACS Nano.

Yoke Khin Yap, a physics professor at Michigan Tech, led the study. He explains that the behavior observed by his team, the atomic level manipulation of gold quantum dots, can be observed with a scanning transmission electron microscope (STEM). The high-power electron beam of STEM allows researchers like Yap to observe atomic movement in real time and the view reveals how the gold atoms interact with the surface of the boron nitride nanotubes. Basically, the gold atoms glide along the surface of the nanotubes and, they stabilize in a flight just above the honeycomb hexagon of the boron nitride nanotubes.

The gold atoms ski along the surface of the boron nitride nanotubes. A better understanding of this phenomenon, using detailed atomic images of a scanning electron microscope (STEM), could help physicists, material scientists and computer engineers to develop better computers, cell phones, portable devices and other electronic devices. Credit: Nicole Kelly / Michigan Tech

The atomic skiing and the stop are related to the so-called selective deposition of energy. In the laboratory, the team takes a series of boron nitride nanotubes and pbades a mist loaded with gold; the gold atoms in the fog stick together as multi-layered nanoparticles or bounce off the nanotube, but some of the more energetic ones slip along the circumference of the nanotube and stabilize, then begin to cluster in monolayers of quantum dots gold. The team shows that gold is preferentially deposited behind other gold particles that have stabilized.

"The surface of boron nitride nanotubes is atomically smooth, there are no defects on the surface, it's a well-arranged honeycomb," Yap said, adding that the nanotubes are chemically inert and that there is no physical link between them. nanotubes and the gold atoms. "It's like skiing: you can not ski on a bumpy, sticky hill without snow, the ideal conditions make it much better, the smooth surface of the nanotubes is like fresh powder."

The search for new materials for future electronics and quantum computing has led researchers to travel many paths. Yap hopes that by demonstrating the effectiveness of gold, other researchers will be inspired to pay attention to other metal monolayers on a molecular scale.

"This is a dream nanotechnology," said Yap. "It's a tuneable molecular-scale technology per atom with an ideal band gap in visible light spectra, and there's a lot of promise in electronic and optical devices."

The next steps of the equipment include a greater characterization and incorporation of the manufacture of the device to demonstrate the all-metallic electronics. Potentially, monolayers of metal atoms could constitute all of the electronics of the future, which will save a large amount of energy and materials of manufacture.

Gold absorbs boron, spits borophene

More information:
Shiva Bhandari et al, Two-dimensional gold quantum dots with adjustable band gaps, ACS Nano (2019). DOI: 10.1021 / acsnano.8b09559

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Michigan Technological University

The golden path to new two-dimensional semiconductors (2019, April 11)
recovered on April 12, 2019

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