Which Transition Metal Atoms Can Be Embedded into Two-Dimensional Molybdenum Dichalcogenides and Add Magnetism?

Karthikeyan, J.; Komsa, Hannu Pekka; Batzill, Matthias; Krasheninnikov, Arkady V.

doi:10.1021/acs.nanolett.9b01555

Cited by 68 publications

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“…Direct substitution can also be achieved via ion implantation, but it is technically difficult, as it requires very low ion energies (below 100 eV) or needs an additional coating of buffer layer and post‐annealing, [ 9 ] as otherwise the ions would pass through the atomically thin target. [ 10,11 ] As for 2D transition metal dichalcogenides (TMDCs), the majority of the direct doping methods lead to doping in the chalcogen sublattice, [ 5 ] while controllable doping of these materials in the TM sublattice is extremely important, because the variation of their valence d‐electrons occupancy results in extensive modification of their electronic structure, exciton characteristics, [ 12 ] magnetism, [ 13–15 ] and catalytic behavior. [ 16 ] Finally, as with bulk system, while the substitutional doping can be realized during growth by using chemical vapor transport (CVT) or chemical vapor deposition (CVD) techniques, [ 17 ] the control over the spatial distribution of dopants still remains challenging, and doping concentrations less than 7% are normally achievable.…”

Section: Figurementioning

confidence: 99%

“…Our calculations further show that adding S or Se atoms (as dimers) markedly lowers the total energy of the system by –3.84, –3.93, –4.21, and –3.26 eV for Ti, V, Cr, and Fe (with respect to the dimer adsorbed on the pristine surface) and explain the mechanism of the dislocation climb (Figure 3e) and eventual disappearance. To get a comprehensive picture, we also studied the energetics of TM atoms in other positions, e.g., in X‐sub positions reported for Mo‐based TMDs, [ 14 ] and also investigated in more detail the behavior of TM atoms in WS 2 and Janus WSeS system. The results are presented in Figure S5, Supporting Information.…”

Section: Figurementioning

confidence: 99%

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Formation of Highly Doped Nanostripes in 2D Transition Metal Dichalcogenides via a Dislocation Climb Mechanism

et al. 2021

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processes such as ion implantation can be used, but this approach tends to create undesirable defects, whose removal then requires additional annealing steps. Recently, lots of research attention has been focused on 2D materials, [1,2] as they not only exhibit great variety in electronic characteristics ranging from insulators to metals, but also possess unique properties related to their reduced dimensionality. While 2D materials can be doped with the same methods as bulk systems, there are approaches that are unique to them. Due to the surface-only geometry, the doping in 2D materials can also be attained by: 1) physical/chemical adsorption; 2) ionicliquid-gating; and 3) direct atomic substitution. [3,4] The surface adsorption and ionic-liquid-gating are basically equivalent to the implementation of charge transfer between the environment and the 2D materials, which are both very effective due the high surface to volume ratio of the 2D materials. However, the difficulties in integration of the system limit the practical applications of these approaches. The direct atomic substitution in 2D materials can be done via, e.g., sulfurization/selenization. [5] Alternatively, vacancies can be produced by irradiation [6,7] or thermal evaporation during annealing, [8] followed by the deposition of doping species. Direct substitution can also be achieved via ion implantation, but it is technically difficult, as it requires very low ion energies (below 100 eV) or needs an additional coating of buffer layer and The ORCID identification number(s) for the author(s) of this article can be found under

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Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Formation of Highly Doped Nanostripes in 2D Transition Metal Dichalcogenides via a Dislocation Climb Mechanism

et al. 2021

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“…The total magnetic moments are 2.0 and 2.3 μ B per cell, respectively. The proposed “X‐sub” configuration, [ 29 ] which can be regarded as a complex consisting Nd S and a S adatom (Nd S + S), is nonmagnetic (see Figure S5, Supporting Information).…”

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confidence: 99%

Defects Engineering Induced Ultrahigh Magnetization in Rare Earth Element Nd‐doped MoS₂

et al. 2020

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Various concentrations (0, 0.5, 1, and 5 at%) of Nd are doped into MoS2 single crystals via ion implantation. Experimental results reveal that Nd exists in the form of trivalent state when the doping concentration is below 5 at% and a variety of defects, such as sulfur and molybdenum vacancies, are formed in Nd‐doped MoS2. Compared to pure MoS2 that only shows diamagnetism, Nd doping successfully induces room‐temperature ferromagnetic ordering. Extremely high magnetization (1640 emu cm−3) is observed in 1 at% Nd‐doped MoS2. First‐principles density functional theory calculations suggest that the various structural defects, including substitutions, vacancies, interstitials, antisites, and their complexes, are magnetic possessing large spin moments. The defects coupled with Nd dopants ferromagnetically may form the bound magnetic polarons to induce ferromagnetic ordering. The work has demonstrated that through defects engineering and rare earth element doping, extremely high magnetization materials can be achieved in layered structured materials. On the other hand, though the experiment work is done by implanting MoS2 single crystals, theoretical calculations indicate that 2D MoS2 with bilayers or a few layers can also result in ultrahigh magnetization.

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“…A number of intrinsic defects have been found to form local moments [27][28][29][30][31] in MX 2 materials and suggestions have been made to make the MX 2 materials magnetic by adsorption of impurity atoms, 27,28,32,33 or by substituting M or X atoms with impurity atoms. 28,[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] Even though the Mermin-Wagner theorem 7,8 tells us that there is no long range ordering in two dimensions for isotropic Heisenberg exchange, few attempts have been made to determine the exchange coupling between magnetic impurities 33,37,38,40,41,47,51 and it was only very recently that the magnetic anistropy of a defect was calculated, for an antisite defect in MoS 2 . 31 Replacing some of the M atoms with Hund's-rule coupled transition metal atoms like Mn or Fe gives rise to deep impurity levels in the semiconductor gap.…”

Section: Introductionmentioning

confidence: 99%

DFT study of itinerant ferromagnetism in p -doped monolayers of MoS2

2019

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We use density functional theory to explore the possibility of making the semiconducting transition-metal dichalcogenide MoS2 ferromagnetic by introducing holes into the narrow Mo d band that forms the top of the valence band. In the single impurity limit, the repulsive Coulomb potential of an acceptor atom and intervalley scattering lead to a twofold orbitally degenerate effective-mass like e state being formed from Mo d x 2 −y 2 and dxy states, bound to the K and K valence band maxima. It also leads to a singly degenerate a 1 state with Mo d 3z 2 −r 2 character bound to the slightly lower lying valence band maximum at Γ. Within the accuracy of our calculations, these e and a 1 states are degenerate for MoS2 and accommodate the hole that polarizes fully in the local spin density approximation in the impurity limit. With spin-orbit coupling included, we find a single ion magnetic anisotropy of ∼ 5 meV favouring out-of-plane orientation of the magnetic moment. Pairs of such hole states introduced by V, Nb or Ta doping are found to couple ferromagnetically unless the dopant atoms are too close in which case the magnetic moments are quenched by the formation of spin singlets. Combining these exchange interactions with Monte Carlo calculations allows us to estimate ordering temperatures as a function of x. For x ∼ 9%, Curie temperatures as high as 100K for Nb and Ta and in excess of 160K for V doping are predicted. Factors limiting the ordering temperature are identified and suggestions made to circumvent these limitations. PACS numbers: 75.70.Ak, 73.22.-f, 75.30.Hx, 75.50.Pp FIG. 2. Schematic of the effective mass acceptor states bound to the valence band maxima (VBM): an e state bound to the K-K VBM and an a 1 state to the Γ VBM. n is the principal quantum number and only n = 1, 2, 3 levels of the Rydberg series are sketched at the Γ point.

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Which Transition Metal Atoms Can Be Embedded into Two-Dimensional Molybdenum Dichalcogenides and Add Magnetism?

Cited by 68 publications

References 52 publications

Formation of Highly Doped Nanostripes in 2D Transition Metal Dichalcogenides via a Dislocation Climb Mechanism

Formation of Highly Doped Nanostripes in 2D Transition Metal Dichalcogenides via a Dislocation Climb Mechanism

Defects Engineering Induced Ultrahigh Magnetization in Rare Earth Element Nd‐doped MoS₂

DFT study of itinerant ferromagnetism in p -doped monolayers of MoS2

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Which Transition Metal Atoms Can Be Embedded into Two-Dimensional Molybdenum Dichalcogenides and Add Magnetism?

Cited by 68 publications

References 52 publications

Formation of Highly Doped Nanostripes in 2D Transition Metal Dichalcogenides via a Dislocation Climb Mechanism

Formation of Highly Doped Nanostripes in 2D Transition Metal Dichalcogenides via a Dislocation Climb Mechanism

Defects Engineering Induced Ultrahigh Magnetization in Rare Earth Element Nd‐doped MoS2

DFT study of itinerant ferromagnetism in p -doped monolayers of MoS2

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Defects Engineering Induced Ultrahigh Magnetization in Rare Earth Element Nd‐doped MoS₂