Revolutionary research by lecturer Feng Ding’s group from the Centre for Multidimensional Carbon materials, within the Institute for Basic Science (IBS), in association with lecturer Jin Zhang’s group, at Peking University and colleagues, has illustrated how to regulate the synthesis of special small carbon cylinders known as carbon nanotubes (CNTs), in order to synthesize horizontal arrays of CNTs with the same structure.
Due to their exceptional mechanical, thermal and electrical properties, CNTs are considered an excellent alternative to silicon for novel generation microelectronics. But, since CNTs electronic properties are structure dependent, finding a reliable way to synthesize CNTs with the same structure, rather than a mix of distinct types, have kept researchers puzzled for the last 20 years.
CNTs resemble sheets of graphene rolled up to form small tubes, 100,000 times thinner than a human hair. In reality, however, no rolling is involved in the synthesis procedures, and CNTs usually grow from the surfaces of tiny metal particles, known as catalysts, via catalytic chemical; vapour deposition. Beyond being a supportive structure, the catalyst decomposes hydrocarbon molecules into carbon atoms that form the carbon nanotubes and facilitates the insertion of carbon atoms into the growing cylinder.
In 2014, Ding and his associates discovered that employing solid metal alloy catalysts, like W6Co7, can result in synthesis of CNTs with particular structures. In their most recent study, they expanded this knowledge much further.
Like in a battleship game where the position of the boats is defined by two numbers, the structure of CNTs is defined by a pair of indices. IBS researchers found they could grow both conducting and semiconducting CNTs with very high selectivity. Such structures are exceedingly desired for feasible applications in transistor devices.
Considering the symmetry of the catalysts, the kinetics of CNT growth and the size of the catalyst particles, the scientists could tune the production of CNTs towards single predominant. “A particular catalyst can produce a particular group of CNTs as they share the same symmetry,” explains Lecturer Ding. Moreover, the CNTs grow in parallel on a substrate and hence can be employed for device applications directly.
The CNT’s purify reached 80-90%, which is among the biggest that has ever been accomplished experimentally. “The theoretical calculations illustrate that the selectivity could be bigger than 99.9%, comprising that there is still a big scope for enhancement,” explains lecturer Ding.
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