By Nick Gilbert
A research team from the Case Western Reserve University has discovered that triangle, cube and other higher-order-structured gold catalysts are capable of growing nanowires two times faster and longer than the process involving standard spherically-shaped catalysts.
The research team comprised of Case Western Reserve University Assistant Professors, R. Mohan Sankaran and Xuan Gao, and graduate students, Dong Liang and Dong Liang, and Hathaway Brown Upper School student, Samantha Reeves. The study findings have been reported in the paper titled ‘Shape-Controlled Au Particles for InAs Nanowire Growth’ in the Nano Letters journal.
These findings pave the way to grow nanowires to rapidly develop sensors for detecting the changes in white and red blood cells, and thus determine different types of cancer. These tiny nanowires hold potential in designing advanced ‘invisible’ computer chips. The researchers used arsenic and indium to grow the nanowires using the bottom-up approach. Nanowires can also be fabricated by cutting a large semiconducting material piece into small wires. This technique is called the top-down approach.
However, it is impractical to produce nanowires below 45 nm using the top-down approach, said Sankaran. On the other hand, nanowires grown from chemical compounds can be as tiny as 10 nm, which means more wires can be placed in a smaller area to achieve better speed. Nevertheless, the bottom-up approach has its own disadvantage of producing wires in bunches compared to the large interwoven structures fabricated using the top-down approach. The challenge is integrating these chemically-grown nanowires in such a way that they should function in intricate electronics like highly-sensitive sensors or computer chips.
During the study, the research team tested the growth of nanowires utilizing both spherically-shaped and preferentially-shaped catalysts under same conditions to eliminate errors during comparisons. The team discovered that the vapor-liquid-solid or VLS growth is not complete. However, more research is required to thoroughly identify the process. The researchers found a connection between growth progression and indium concentration when they shot electrons at the nanowires, causing the release of high-energy X-rays. This process is termed as energy-dispersive X-ray spectroscopy. The level of this energy release was utilized to identify the nanowires’ chemical properties.
Gao and Sankaran intend to study the link between catalyst shape and the nanowires’ structural characteristics to improve the VLS model and realize nanowire integration in new technology.