"Having a method to sculpt crystals at the nanoscale precisely, quickly and without the need for traditional top-down processes presents major advantages for widespread utilization of nanomaterials in technology applications."Thomas Kempa, Johns Hopkins University
Researchers at Johns Hopkins University have developed a new method for producing atomically thin semiconducting crystals that could lead to more powerful and compact electronic devices.
By using specially treated silicon surfaces to tailor the crystals' size and shape, the researchers have found a potentially faster and less expensive way to produce next-generation semiconductor crystals for microchips. The crystalline materials produced this way could, in turn, allow new scientific discoveries and accelerate technological developments in quantum computing, consumer electronics, and higher efficiency solar cells and batteries. The researchers report their new method in a paper in Nature Nanotechnology.
"Having a method to sculpt crystals at the nanoscale precisely, quickly and without the need for traditional top-down processes presents major advantages for widespread utilization of nanomaterials in technology applications," said Thomas Kempa, a chemistry professor at Johns Hopkins University, who directed the research.
Kempa's team first doused silicon substrates – the supports used widely in industrial settings to process semiconductors into devices – with phosphine gas. When crystals were coaxed to grow on these phosphine-treated silicon supports, the researchers found that they grew into structures that were far smaller and of higher quality than crystals prepared through traditional means.
The reaction of phosphine with the silicon support caused the formation of a new ‘designer surface’ that spurred the crystals to grow as horizontal ‘ribbons’, as opposed to the planar and triangularly shaped sheets that are typically produced. Moreover, the uniform complexion and clean-edged structure of these ribbons rivaled the quality of nanocrystals prepared through industry-standard patterning and etching processes, which are often laborious, lengthy and expensive, Kempa said.
The nanocrystals prepared in this study were transition metal dichalcogenides (TMDs). Like graphene, TMDs have enjoyed widespread attention for possessing powerful properties that are a unique consequence of their two-dimensional scale. But conventional processing methods struggle to readily alter the texture of TMDs in ways that suit the development of better-performing technologies.
Notably, the versions of TMDs that Kempa and his team were able to create were so small that they dubbed them ‘one-dimensional’ to differentiate them from the usual two-dimensional sheets most researchers are familiar with.
Kempa and his team were able to directly grow the crystals to their precise specifications by changing the amount of phosphine, while the ‘designer substrates’ proved to be reusable, saving money and time on processing. The resulting ribbon-shaped, one-dimensional crystals emit light whose color can be tuned by adjusting the ribbon width, indicating their potential promise in quantum information applications. In addition, the elegant quality of these crystals could render them more efficient at conducting and converting energy in solar cells or catalysts.
"We are contributing a fundamental advance in rational control of the shape and dimension of nanoscale materials," Kempa said. This method can "sculpt nanoscale crystals in ways that were not readily possible before," he added. "Such precise synthetic control of crystal size at these length scales is unprecedented."
"Our method could save substantial processing time and money," he added. "Our ability to control these crystals at will could be enabling of applications in energy storage, quantum computing and quantum cryptography."
This story is adapted from material from Johns Hopkins University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.