Polarity effects in unsupported polar nanoribbons

Güller, Francisco; Llois, A.M.; Goniakowski, Jacek; Noguera, Claudine

doi:10.1103/physrevb.87.205423

Cited by 31 publications

(57 citation statements)

References 52 publications

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“…The edge energy of a-TiS 3 NRs oscillates with different ribbon widths and ranges from 454 to 475 meV/Å. This is close to the values of many other TMC nanoribbons such as ribbons of MoS 2 , WS 2 , and ZrS 2 [39]. The situation in b-TiS 3 NRs is, however, much different; the edge energy is typically around 60 meV/Å and slightly decreases as the ribbon width increases.…”

Section: Structural Properties and Edge Energeticsmentioning

confidence: 68%

“…The situation in b-TiS 3 NRs is, however, much different; the edge energy is typically around 60 meV/Å and slightly decreases as the ribbon width increases. Compared with the edge energies of graphene and many other TMC nanoribbons, which are on the order of 1 eV/Å [39,40], b-TiS 3 NRs have much lower edge energy, suggesting that formation of b-TiS 3 NRs from 2D TiS 3 could be much easier. In fact, the experimentally reported TiS 3 NRs are along the b direction [20].…”

Section: Structural Properties and Edge Energeticsmentioning

confidence: 99%

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TiS3nanoribbons: Width-independent band gap and strain-tunable electronic properties

et al. 2015

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The electronic properties, carrier mobility, and strain response of TiS 3 nanoribbons (TiS 3 NRs) are investigated by first-principles calculations. We found that the electronic properties of TiS 3 NRs strongly depend on the edge type (a or b). All a-TiS 3 NRs are metallic with a magnetic ground state, while b-TiS 3 NRs are direct band gap semiconductors. Interestingly, the size of the band gap and the band edge position are almost independent of the ribbon width. This feature promises a constant band gap in a b-TiS 3 NR with rough edges, where the ribbon width differs in different regions. The maximum carrier mobility of b-TiS 3 NRs is calculated by using the deformation potential theory combined with the effective mass approximation and is found to be of the order 10 3 cm 2 V −1 s −1 . The hole mobility of the b-TiS 3 NRs is one order of magnitude lower, but it is enhanced compared to the monolayer case due to the reduction in hole effective mass. The band gap and the band edge position of b-TiS 3 NRs are quite sensitive to applied strain. In addition we investigate the termination of ribbon edges by hydrogen atoms. Upon edge passivation, the metallic and magnetic features of a-TiS 3 NRs remain unchanged, while the band gap of b-TiS 3 NRs is increased significantly. The robust metallic and ferromagnetic nature of a-TiS 3 NRs is an essential feature for spintronic device applications. The direct, width-independent, and strain-tunable band gap, as well as the high carrier mobility, of b-TiS 3 NRs is of potential importance in many fields of nanoelectronics, such as field-effect devices, optoelectronic applications, and strain sensors.

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Section: Structural Properties and Edge Energeticsmentioning

confidence: 68%

Section: Structural Properties and Edge Energeticsmentioning

confidence: 99%

TiS3nanoribbons: Width-independent band gap and strain-tunable electronic properties

et al. 2015

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“…III B. In polar lattices such as MX 2 the CNL does not fix the intrinsic Fermi level, unlike in a nonpolar lattice such as graphene [61,62]. In a finite-sized MX 2 sample, electrons can be redistributed among all the edges in the sample, driven by the internal electric field set up by the intrinsic polarization of the material.…”

Section: Zigzag and Armchair Edgesmentioning

confidence: 99%

“…In addition, as MX 2 compounds are polar materials, an internal electric field is created if a crystallite is terminated by polar edges [61,62]. Such an electric field can cause a long-range charge transfer between different edges, even if the bulk material does not contain any impurities.…”

Section: Charge-neutrality Levelmentioning

confidence: 99%

Green's function approach to edge states in transition metal dichalcogenides

2016

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The semiconducting two-dimensional transition metal dichalcogenides MX 2 show an abundance of onedimensional metallic edges and grain boundaries. Standard techniques for calculating edge states typically model nanoribbons, and require the use of supercells. In this paper, we formulate a Green's function technique for calculating edge states of (semi-)infinite two-dimensional systems with a single well-defined edge or grain boundary. We express Green's functions in terms of Bloch matrices, constructed from the solutions of a quadratic eigenvalue equation. The technique can be applied to any localized basis representation of the Hamiltonian. Here, we use it to calculate edge states of MX 2 monolayers by means of tight-binding models. Aside from the basic zigzag and armchair edges, we study edges with a more general orientation, structurally modifed edges, and grain boundaries. A simple three-band model captures an important part of the edge electronic structures. An 11-band model comprising all valence orbitals of the M and X atoms is required to obtain all edge states with energies in the MX 2 band gap. Here, states of odd symmetry with respect to a mirror plane through the layer of M atoms have a dangling-bond character, and tend to pin the Fermi level.

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“…[185,186] Surface states may originate from different sources, e.g. dangling bonds or polar discontinuities [187,188], but what makes topological insulators special is that metallic states are protected by time-reversal symmetry. Therefore, they are robust against backscattering and in the presence of non-magnetic perturbations.…”

Section: Edge States In Monolayer Mos 2 Nanostructuresmentioning

confidence: 99%

Electronic structure of quantum dots: response to the environment and externally applied fields

Ortí¹

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AgraïmentsLa present Tesi doctoralés el resultat final de quatre anys de treball i esforç en què he tingut la sort de comptar amb el suport de companys, familiars i amics que han compartit amb mi aquesta enriquidora experiència. Sens dubte, el treball que ací es mostra no haguera sigut possible sense la seua ajuda.En primer lloc, voldria agrair a Josep Planelles i Juan Ignacio Climente el haver-me oferit la possibilitat de realitzar aquest projecte de Tesi sota la seua supervisió. Durant tot el temps que he tingut el plaer de treballar amb ells han mostrat un gran interès i una dedicació plena en proporcionar-me la millor formació investigadora tenint sempre present el que seria millor per al meu futur. De la mateixa manera, el meu agraïmentés extensiu a la resta de membres del grup de Química Quàntica Fernando Rajadell, José Luis Movilla, Miquel Royo i Ana Ballester que d'una manera o altra han contribuït a la realització d'aquesta Tesi. En especial vull destacar a Ana B, amb qui vaig tindre la sort de compartir laboratori durant els primers anys de doctorat i que prompte es va convertir en una molt bona amiga. D'altra banda, voldria mostrar també la meua gratitud als amics que han estat al meu costat en el dia a dia durant aquests anys i que han compartit amb mi molts bons moments dintre i fora de la universitat. En concret vull destacar a Ana M, David, Erica, Neus, Paula i, com no, a chéritounet Loucou. A més, cal mencionar a tots els membres del Departament de Química Física i Analítica, especialment a Merche per la seva predisposició a ajudar-me amb tota la paperassa i els tràmits burocràtics. Done també les gràcies a Sergio E. Ulloa per donar-me l'oportunitat de realitzar una estada breu en el seu grup de recerca en la Universitat d'Ohio (Estats Units), així com a tots els membres del grup per la seua acollida.Finalment, voldria agrair de cor als meus pares el suport i la confiança incondicionals que m'han donat durant tota la meua vida. Perquè són els principals responsables de que haja arribat fins ací, els dedique aquesta Tesi.

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Polarity effects in unsupported polar nanoribbons

Cited by 31 publications

References 52 publications

TiS3nanoribbons: Width-independent band gap and strain-tunable electronic properties

TiS3nanoribbons: Width-independent band gap and strain-tunable electronic properties

Green's function approach to edge states in transition metal dichalcogenides

Electronic structure of quantum dots: response to the environment and externally applied fields

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