Narrow strips of single-layer graphene called Graphene nanoribbon shows interesting physical, thermal, optical, and electrical properties due to the interplay between their structures, specifically crystal and electronic structures.
Phys.org said, these novel features have pushed GNRs to the forefront in quest for new ways for the advancement of next-generation nanotechnologies.
While bottom-up fabrication approaches now allow the fusion of a broad range of graphene nanoribbons featuring well-defined edge widths, geometries and heteroatom integrations, the issue of whether or not structural disorder exists in these atomically accurate GNRs, and up to what degree, is still subject to discussion and argument.
Accordingly, the answer to this issue is of critical importance to any probable applications or resulting devices.
Collaboration between Chair of Computational Condensed Matter Physics theory group at EPFL of Oleg Yazyev, and experimental nanotech@surface Laboratory at Empa of Roman Fasel, has generated two papers that searched for this issue in two graphene nanoribbons called armchair-edged and zigzag-edged.
'Bite' Defects
According to former Ph.D. student, Michele Pizzochero, from Oleg Yazyev's lab at EPFL, and now a Harvard University post-doctoral researcher, imperfections have known to play a vital role in shaping several functionalities in crystals.
A similar SciFi Insight report said, in these papers, they have shown ubiquitous "bite" defects, called missing groups of carbon atoms, as the fundamental type of structural disorder in graphene GNRs fabricated through on-surface synthesis.
Even though they found that bite defects are degrading the electronic devices' performance based on GNRs, in some circumstances, these imperfections may provide exciting opportunities for spintronic applications, because of their unusual magnetic properties.
The study, Quantum electronic transport across 'bite' defects in graphene nanoribbons, published in 2D Materials, particularly looks at nine-atom wide armchair graphene nanoribbons or 9-AGNRs.
The mechanical strength, long-lasting stability under ambient conditions, easy transmissibility onto target substrates, fabrication's scalability, as well as appropriate band-gap width of these GNRs have made them among the most promising contenders of incorporation as active channels in the so-called FETs or field-effect transistors.
Among the graphene-based devices realized to date, the 9-AGNR-FETs exhibited the highest performance, the study specified.
Zigzag GNRs
In the research, Edge Disorder in Bottom-Up Zigzag Graphene Nanoribbons: Implications for Magnetism and Quantum Electronic Transport, published in The Journal of Physical Chemistry Letters, the same research team combined scanning probe microscopy studies and first-principles computations to investigate structural disorder, as well as its impact on magnetism and electronic transport in what's called the ZGNRs or zigzag GNRs.
This paper describes the ZGNRs as unique due to their unconventional zero-metal magnetic disorder that, based on predictions, is retained up to room temperature.
These type of GNRs hold magnetic moments that are paired "ferromagnetically" along the edge, and "antiferromagnetically" through it, and it has been presented that both the electronic and magnetic structures can be reduced to a large degree, for instance, electric fields, charge doping, defect engineering or lattice deformations.
'Local Magnetic Moment'
Essentially, the effect of such bite defects on the electronic composition, as well as quantum transport properties of 6-ZGNRs is, once more, investigated theoretically.
The researchers found that the defect's introduction, similarly to AGNRs, results in a substantial disruption of the conductance.
Moreover, in this nanostructure, these unintended defects induce sublattice and spin imbalance, leading to a local magnetic moment.
A comparison between these two GNRs of equal width presents that transport through the former is less sensitive to the introduction of defects, both single and multiple, than in the latter.
In general, this particular study provides a worldwide image of the effect of these odd bite defects on the low-energy electronic composition of bottom-up GNRs.
Future studies, explained by the researchers, might concentrate on the examination of other point defect types experimentally observed at such nanoribbons' edges.
Related information is shown on Bristol Composites Institute's YouTube video below:
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