MXene nanoribbons

Quasi-one-dimensional nanoribbons have great potential for applications in nanoelectronics and nanospintronics due to their unique quantum confinement effects. In this work, first-principles calculations are carried out to predict the stability as well as magnetic and electronic properties of MXene nanoribbons with either zigzag- or armchair-terminated edges. Three types of MXene recently realized experimentally, i.e. Ti₂C, Ti₃C₂ and V₂C, are considered to construct their corresponding MXene nanoribbons. In addition, the O-functionalized Ti₂C and Ti₃C₂ nanoribbons are also investigated. The effect of functionalization is studied by comparing different functional groups including OH, F and O. Six zigzag and two armchair families are distinguished according to different ribbon edges. Our results show that all the investigated bare MXenes are metallic and exhibit certain magnetic moments in their ground states, irrespective of the ribbon width and ribbon type. Remarkable edge reconstructions are observed for all types of nanoribbon. We further show that hydrogen passivation can lead to the increase of the magnetic moments of Ti₂C and V₂C nanoribbons due to charge transfer. For O-functionalized Ti₂C nanoribbons, our calculations indicate that some of them exhibit semiconducting properties dependent on edge configurations. In particular, the band gap of armchair Ti₂CO₂ nanoribbons with a width of 7.34 Å is found to be around 1.0 eV, which is significantly enhanced compared to the 0.4 eV of a pristine Ti₂CO₂ layer. The stabilities of these nanoribbons are evaluated by virtue of their binding energies, formation energies and edge energies and we show that functionalized MXene nanoribbons are more stable than bare ribbons. Our results thus provide strong evidence for the effectiveness of nanostructuring on the electronic and magnetic properties of MXenes.