| 1. |
- Jena, Anjan Kumar, et al.
(författare)
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Strain-mediated ferromagnetism and low-field magnetic reversal in Co doped monolayer WS2
- 2022
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Strain-mediated magnetism in 2D materials and dilute magnetic semiconductors hold multifunctional applications for future nano-electronics. Herein, First principles calculations are employed to study the influence of biaxial strain on the magnetic properties of Co-doped monolayer WS2. The non-magnetic WS2 shows ferromagnetic signature upon Co doping due to spin polarization, which is further improved at low compressive (-2 %) and tensile (+2 %) strains. From the PDOS and spin density analysis, the opposite magnetic ordering is found to be favourable under the application of compressive and tensile strains. The double exchange interaction and p-d hybridization mechanisms make Co-doped WS2 a potential host for magnetism. More importantly, the competition between exchange and crystal field splittings, i.e. (Delta(ex) > Delta(cfs)), of the Co-atom play pivotal roles in deciding the values of the magnetic moments under applied strain. Micromagnetic simulation reveals, the ferromagnetic behavior calculated from DFT exhibits low-field magnetic reversal (190 Oe). Moreover, the spins of Co-doped WS2 are slightly tilted from the easy axis orientations showing slanted ferromagnetic hysteresis loop. The ferromagnetic nature of Co-doped WS2 suppresses beyond +/- 2 strain, which is reflected in terms of decrease in the coercivity in the micromagnetic simulation. The understanding of low-field magnetic reversal and spin orientations in Co-doped WS2 may pave the way for next-generation spintronics and straintronics applications.
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| 2. |
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| 3. |
- Mallik, Sameer Kumar, et al.
(författare)
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Transition metal substituted MoS2/WS2 van der Waals heterostructure for realization of dilute magnetic semiconductors
- 2022
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier. - 0304-8853 .- 1873-4766. ; 560
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Tidskriftsartikel (refereegranskat)abstract
- Atomically thin doped two dimensional (2D) layered materials manifest excellent magnetic features beneficial to the potential applications in spintronics. With the implementation of extensive first principles calculations, we demonstrate the MS2 (M = Mo, W) monolayers, as well as their van der Waals (vdW) hetero-bilayers as promising candidates for the successful realization of 2D dilute magnetic semiconductors with the incorporation of Mn and Co dopants. Under various pairwise doping configurations at different host atom sites, we report the electronic properties modifications induced change in magnetic exchange interactions. The magnetic coupling among the dopant pairs can be tuned between FM and AFM orderings via suitable doping adjustments. The developed interlayer exchange coupling between the vdW layers leads to strong and long-ranged ferromagnetic interactions which unleash robust magnetic moments with stable doping configurations. Our findings address the novel magnetic behavior of the layered vdW heterostructures and may further guide the future experimental efforts for the possible applications in modern electronics and nanoscale magnetic storage devices.
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| 4. |
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| 5. |
- Sahoo, Sandhyarani, et al.
(författare)
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Electric Field-Modulated Charge Transfer in Geometrically Tailored MoX2/WX2 (X = S, Se) Heterostructures
- 2021
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:40, s. 22360-22369
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Tidskriftsartikel (refereegranskat)abstract
- Light-induced interlayer charge transfer in staggered-type heterostructures (HSs) in transition-metal dichalcogenides provides the opportunity to improve the performance of optoelectronic applications. Herein, we employ density functional theory to investigate the vertical electric-field-controlled interlayer charge transfer in stacked MoX2/WX2 (X=S, Se) HSs. Upon application of electric field from -3 to 3 V/nm, we observe the band-alignment transition, band inversion, and offset variations in these HSs. Furthermore, these electric fields are found to modulate charge localization/delocalization across the layers, which provides insight into charge transfer. The positive electric field is supposed to localize the charges in WS2, whereas the charges are localized in MoS2 at negative electric field. Based on charge localization/delocalization, our study suggests that the interlayer hole transfer upon MoS2 photoexcitation can be suppressed at higher positive electric fields, whereas electron transfer can be blocked by excitation of WS2. In contrast, negative electric fields (of -3 V/nm) can induce interlayer hole and electron transfer. Owing to the tunability of interlayer charge transfer by means of a vertical electric field, our findings bear paramount importance in modulating electron-hole recombination and charge-transfer time, which is beneficial for future optoelectronic devices.
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| 6. |
- Sharma, Neha Kapila, et al.
(författare)
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Electronic bandstructure modulation of MoX2/ZnO(X:S,Se) heterostructure by applying external electric field
- 2022
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Ingår i: SURFACES AND INTERFACES. - : Elsevier. - 2468-0230. ; 29
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Tidskriftsartikel (refereegranskat)abstract
- The electronic properties of 2-Dimensional Van der Waals heterostructure of MX2(M:Mo, X:S, Se) and graphenelike ZnO by applying an external electric field(EF) in the range -0.50V/angstrom to 1.0V/angstrom is studied using first principles calculations. The effect of the transverse electric field is measured in terms of modulation of the electronic energy bandgap and change in the band alignment properties. The bandstructure of MoS2/ZnO heterostructure(HS) shows an indirect bandgap of 1.61eV with a type-II band alignment and a large built-in electric field of 7.42eV with a valence band offset of 1.22eV across the interface. The bandstructure of MoSe2/ZnO shows a direct bandgap of 1.81eV with type-I alignment and a built-in electric field of 3.64eV with a band offset of 0.31eV. The charge density is localized on MoS2 and ZnO in VBM and CBM respectively in MoS2/ZnO HS, whereas in MoSe2/ZnO, both VBM and CBM are localized on MoSe2. With a perpendicular electric field applied across the HS, re-alignment of bandstructure and modulation of bandgap in both the HSs occurs. The energy bandgap increases linearly with the applied electric field for MoS2/ZnO(1.1-2.2eV) and remains almost constant (1.81eV) in the range -0.50V/angstrom to 0.50V/angstrom followed by a small decrease with an increase in electric field (1.60 for EF=+/- 1.0V/angstrom). A cross-over in the bandgap type from indirect(type-II)-> direct(type-I) in MoS2-ZnO and direct(type-I) to indirect(type-II) in MoSe2/ZnO has been observed at a critical value of electric field EF=0.75V/ angstrom. The cross-over in band structure is consistent with the charge transfer pattern observed on the application of electric field. Tuning the electronic bandgap and changing the band-alignment with an external electric field opens a way to design futuristic electronic and optical devices.
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