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“Point defects in a two-dimensional ZnSnN₂, nanosheet : a first-principles study on the electronic and magnetic properties”. Bafekry A, Faraji M, Fadlallah MM, Mortazavi B, Ziabari AA, Khatibani AB, Nguyen C V, Ghergherehchi M, Gogova D, Journal Of Physical Chemistry C 125, 13067 (2021). http://doi.org/10.1021/ACS.JPCC.1C03749
Abstract: The reduction of dimensionality is a very effective way to achieve appealing properties in two-dimensional materials (2DMs). First-principles calculations can greatly facilitate the prediction of 2DM properties and find possible approaches to enhance their performance. We employed first-principles calculations to gain insight into the impact of different types of point defects (vacancies and substitutional dopants) on the electronic and magnetic properties of a ZnSnN2 (ZSN) monolayer. We show that Zn, Sn, and N + Zn vacancy-defected structures are p-type conducting, while the defected ZSN with a N vacancy is n-type conducting. For substitutional dopants, we found that all doped structures are thermally and energetically stable. The most stable structure is found to be B-doping at the Zn site. The highest work function value (5.0 eV) has been obtained for Be substitution at the Sn site. Li-doping (at the Zn site) and Be-doping (at the Sn site) are p-type conducting, while B-doping (at the Zn site) is n-type conducting. We found that the considered ZSN monolayer-based structures with point defects are magnetic, except those with the N vacancy defects and Be-doped structures. The ab initio molecular dynamics simulations confirm that all substitutionally doped and defected structures are thermally stable. Thus, our results highlight the possibility of tuning the magnetism in ZnSnN2 monolayers through defect engineering.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 4.536
DOI: 10.1021/ACS.JPCC.1C03749
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“Investigation of strain and doping on the electronic properties of single layers of C₆N₆, and C₆N₈: a first principles study”. Bafekry A, Nguyen C V, Goudarzi A, Ghergherehchi M, Shafieirad M, Rsc Advances 10, 27743 (2020). http://doi.org/10.1039/D0RA04463F
Abstract: In this work, by performing first-principles calculations, we explore the effects of various atom impurities on the electronic and magnetic properties of single layers of C(6)N(6)and C6N8. Our results indicate that atom doping may significantly modify the electronic properties. Surprisingly, doping Cr into a holey site of C(6)N(6)monolayer was found to exhibit a narrow band gap of 125 meV upon compression strain, considering the spin-orbit coupling effect. Also, a C atom doped in C(6)N(8)monolayer shows semi-metal nature under compression strains larger than -2%. Our results propose that Mg or Ca doped into strained C(6)N(6)may exhibit small band gaps in the range of 10-30 meV. In addition, a magnetic-to-nonmagnetic phase transition can occur under large tensile strains in the Ca doped C(6)N(8)monolayer. Our results highlight the electronic properties and magnetism of C(6)N(6)and C(6)N(8)monolayers. Our results show that the electronic properties can be effectively modified by atom doping and mechanical strain, thereby offering new possibilities to tailor the electronic and magnetic properties of C(6)N(6)and C(6)N(8)carbon nitride monolayers.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.9
Times cited: 11
DOI: 10.1039/D0RA04463F
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“Interfacial characteristics, Schottky contact, and optical performance of a graphene/Ga2SSe van der Waals heterostructure: Strain engineering and electric field tunability”. Nguyen HTT, Obeid MM, Bafekry A, Idrees M, Vu TV, Phuc H V, Hieu NN, Le Hoa T, Amin B, Nguyen C V, Physical Review B 102, 075414 (2020). http://doi.org/10.1103/PHYSREVB.102.075414
Abstract: Two-dimensional graphene-based van der Waals heterostructures have received considerable interest because of their intriguing characteristics compared with the constituent single-layer two-dimensional materials. Here, we investigate the interfacial characteristics, Schottky contact, and optical performance of graphene/Ga2SSe van der Waals (vdW) heterostructure using first-principles calculations. The effects of stacking patterns, electric gating, and interlayer coupling on the interfacial properties of graphene/Ga2SSe heterostructures are also examined. Our results demonstrate that the Dirac cone of graphene is well preserved at the F point in all stacking patterns due to the weak vdW interactions, which keep the heterostructures feasible such that they can be obtained in further experiments. Moreover, depending on the stacking patterns, a small band gap of about 13-17 meV opens in graphene and has a high carrier mobility, indicating that the graphene/Ga2SSe heterostructures are potential candidates for future high-speed nanoelectronic applications. In the ground state, the graphene/Ga2SSe heterostructures form an n-type Schottky contact. The transformation from an n-type to a p-type Schottky contact or to an Ohmic contact can be forced by electric gating or by varying the interlayer coupling. Our findings could provide physical guidance for designing controllable Schottky nanodevices with high electronic and optical performances.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 12
DOI: 10.1103/PHYSREVB.102.075414
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“First-principles investigation of nonmetal doped single-layer BiOBr as a potential photocatalyst with a low recombination rate”. Obeid MM, Stampfl C, Bafekry A, Guan Z, Jappor HR, Nguyen C V, Naseri M, Hoat DM, Hieu NN, Krauklis AE, Tuan V Vu, Gogova D, Physical Chemistry Chemical Physics 22, 15354 (2020). http://doi.org/10.1039/D0CP02007A
Abstract: Nonmetal doping is an effective approach to modify the electronic band structure and enhance the photocatalytic performance of bismuth oxyhalides. Using density functional theory, we systematically examine the fundamental properties of single-layer BiOBr doped with boron (B) and phosphorus (P) atoms. The stability of the doped models is investigated based on the formation energies, where the substitutional doping is found to be energetically more stable under O-rich conditions than under Bi-rich ones. The results showed that substitutional doping of P atoms reduced the bandgap of pristine BiOBr to a greater extent than that of boron substitution. The calculation of the effective masses reveals that B doping can render the electrons and holes of pristine BiOBr lighter and heavier, respectively, resulting in a slower recombination rate of photoexcited electron-hole pairs. Based on the results of HOMO-LUMO calculations, the introduction of B atoms tends to increase the number of photocatalytically active sites. The top of the valence band and the conduction band bottom of the B doped BiOBr monolayer match well with the water redox potentials in an acidic environment. The absorption spectra propose that B(P) doping causes a red-shift. Overall, the results predict that nonmetal-doped BiOBr monolayers have a reduced bandgap, a slow recombination rate, more catalytically active sites, enhanced optical absorption edges, and reduced work functions, which will contribute to superior photocatalytic performance.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.3
Times cited: 18
DOI: 10.1039/D0CP02007A
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“A van der Waals heterostructure of MoS₂/MoSi₂N₄, : a first-principles study”. Bafekry A, Faraji M, Ziabari AA, Fadlallah MM, Nguyen C V, Ghergherehchi M, Feghhi SAH, New Journal Of Chemistry 45, 8291 (2021). http://doi.org/10.1039/D1NJ00344E
Abstract: Motivated by the successful preparation of MoSi2N4 monolayers in the last year [Y.-L. Hong et al., Science, 2020, 369, 670-674], we investigate the structural, electronic and optical properties of the MoS2/MoSi2N4 heterostructure (HTS). The phonon dispersion and the binding energy calculations refer to the stability of the HTS. The heterostructure has an indirect bandgap of 1.26 (1.84) eV using PBE (HSE06) which is smaller than the corresponding value of MoSi2N4 and MoS2 monolayers. We find that the work function of the MoS2/MoSi2N4 HTS is smaller than the corresponding value of its individual monolayers. The heterostructure structure can enhance the absorption of light spectra not only in the ultraviolet region but also in the visible region as compared to MoSi2N4 and MoS2 monolayers. The refractive index behaviour of the HTS can be described as the cumulative effect which is well described in terms of a combination of the individual effects (the refractive index of MoSi2N4 and MoS2 monolayers).
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.269
DOI: 10.1039/D1NJ00344E
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“A type-II GaSe/HfS₂, van der Waals heterostructure as promising photocatalyst with high carrier mobility”. Obeid MM, Bafekry A, Rehman SU, Nguyen C V, Applied Surface Science 534, 147607 (2020). http://doi.org/10.1016/J.APSUSC.2020.147607
Abstract: In this paper, the electronic, optical, and photocatalytic properties of GaSe/HfS2 heterostructure are studied via first-principles calculations. The stability of the vertically stacked heterobilayers is validated by the binding energy, phonon spectrum, and ab initio molecular dynamics simulation. The results reveal that the most stable GaSe/HfS2 heterobilayer retains a type-II alignment with an indirect bandgap 1.40 eV. As well, the results also show strong optical absorption intensity in the studied heterostructure (1.8 x 10(5) cm(-1)). The calculated hole mobility is 1376 cm(2) V-1 s(-1), while electron mobility reaches 911 cm(2) V-1 s(-1) along the armchair and zigzag directions. By applying an external electric field, the bandgap and band offset of the designed heterostructure can be effectively modified. Remarkably, a stronger external electric field can create nearly free electron states in the vicinity of the bottom of the conduction band, which induces indirect-to-direct bandgap transition as well as a semiconductor-to-metal transition. In contrast, the electronic properties of GaSe/HfS2 heterostructure are predicted to be insensitive to biaxial strain. The current work reveals that GaSe/HfS2 heterostructure is a promising candidate as a novel photocatalytic material for hydrogen generation in the visible range.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 6.7
Times cited: 4
DOI: 10.1016/J.APSUSC.2020.147607
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