Achieving edge-closed graphene nanoribbons by squashing carbon nanotubes

Long, slender graphene nanoribbons (GNRs) with clean edges, sizable bandgap and excessive mobility are extremely fascinating for digital and optoelectronic purposes. However, effectively making ready such GNRs is tough. Recently, Changxin Chen and his colleagues report that sub-10-nm-wide semiconducting graphene nanoribbons with atomically clean closed edges might be produced by squashing carbon nanotubes utilizing a high-pressure and thermal remedy. The research was printed on-line September 6 in Nature Electronics.

One main impediment to the applying of graphene in electronics and optoelectronics has been that two-dimensional graphene is a semimetal with the zero bandgap. One answer is to make use of one-dimensional graphene nanoribbons (GNRs) with a slender width. Previous research had demonstrated that the GNRs with a width of

On the opposite hand, it’s nonetheless a big problem to acquire the 100% semiconducting single-walled carbon nanotubes (SWCNTs) based mostly on current separation or progress know-how of CNTs. “This also grants narrow GNRs a key advantage over SWCNTs in producing all-semiconducting devices for the application in future integrated circuits,” stated Changxin Chen, the primary writer and corresponding writer of this work and a professor of digital science and know-how at Shanghai Jiao Tong University. 

Unfortunately, prime quality GNRs which might be ultra-narrow and lengthy are tough to synthesize—notably ones with clean edges all through the ribbon size. Thus, a way to effectively produce slender and lengthy GNRs with atomically clean edges is an pressing focus of the analysis neighborhood.

In the work, a diamond anvil cell (DAC) was used for the high-pressure remedy of CNTs. The CNT samples have been loaded and sealed in a pattern chamber within the centre of a pre-indented tungsten gasket that was then compressed between two diamond anvils. Figure 1 illustrates the structural change in CNTs earlier than and after the high-pressure and thermal remedy, the place the pristine CNTs are squashed into GNRs after remedy. The utility of a excessive non-hydrostatic stress and appropriate thermal remedy together with the stabilizing impact of innate defects in CNTs contribute to the conclusion of irreversible radial deformation for CNTs. This makes CNTs be squashed into GNRs. The GNRs obtained from squashed CNTs have atomically clean, closed edges and few defects.

With this method, GNRs narrower than 5 nm have been obtained, and a GNR width right down to 1.4 nm was recorded, which is the one of many narrowest amongst GNRs fabricated utilizing top-down approaches reported thus far. Edge-opened GNRs may be ready by way of utilizing an oxidant, HNO3, to selectively etch the perimeters of the squashed CNTs below excessive stress. A excessive yield as much as 54% could possibly be achieved to squash single-walled and double-walled CNTs into edge-closed GNRs. A typical field-effect transistor (FET) constructed by a 2.8-nm-wide edge-closed GNR reveals a excessive complete efficiency with excessive Ion/Ioff ratio (>10^4), on-state conductivity (7.42 mS) and system mobility (2,443 cm^2 V^−1 s^−1) achieved concurrently. And a bandgap of ~494 meV is estimated for this GNR. High-yield synthesis of slender semiconducting GNRs with high mobility and sizable bandgap is essential for its large-scale system integration.

The technique on this work present a route to provide high-quality, slender, and lengthy semiconducting GNRs and to manage the GNR’s edge sorts for exploring their basic properties and sensible purposes in electronics and optoelectronics. It is a major advance within the manufacturing of high-quality GNRs and high-performance GNRFETs. “Comparing with the methods reported earlier, this new approach is capable of producing much narrower GNRs,” Changxin Chen stated. “Moreover, the atomically smooth edges throughout the entire GNR can be achieved by our method, resulting in high material and device mobility.”

“Taking advantage of our method’s high yield, it is hopeful to scale up the synthesis by further using a multi-anvil apparatus or a large-volume press. Importantly, this method can also be extended to make other material-based nanoribbons from squashed nanotubes and to flatten other fullerene materials,” stated Changxin Chen.

Provided by
Shanghai Jiao Tong University