Scanning Tunneling Microscopy Chemical Signature of Point Defects on the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow><mml:mi mathvariant="normal">M</mml:mi><mml:mi mathvariant="normal">o</mml:mi><mml:mi mathvariant="normal">S</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:mo stretchy="false">(</mml:mo><mml:mn>0001</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math>Surface

Fuhr, J. D.; Saúl, Andrés; Sofo, Jorge O.

doi:10.1103/physrevlett.92.026802

Cited by 111 publications

(76 citation statements)

References 19 publications

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“…However, sulfur vacancy (O S ) and MoS divacancy (O M oS ) were found not to induce any magnetism in contrast to the triple vacancy (O M oS 2 ) which induces magnetic features [13]. The substitution of a S-atom by atoms of complete d band (Pd and Au) was found not to lead to magnetic polarization except for a slight modification of the DOS near the Fermi energy [15]. On the other hand, substitution of a S-atom by atoms with incomplete d band atoms (Fe and V) was found to induce spin polarization and significant modification of the states near the band edges [15].…”

Section: Introductionmentioning

confidence: 99%

“…Magnetism has been confirmed in the 2D's VS 2 and VSe 2 [7] and in metal intercalated TMDs M x NbSe 2 , (M: Fe and Cu [8]). However, the structural analogue of graphene with the single layer TMDs [9][10][11] has led to the search for magnetism in doped TMDs of zero-dimensional (0D) [9,10], one-dimensional (1D) [12] and two-dimensional (2D) [4][5][6][13][14][15] form.…”

Section: Introductionmentioning

confidence: 99%

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Tunable magnetic properties of transition metal dopedMoS2

2014

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We report a detailed investigation of the electronic and magnetic properties of the transitionmetal (TM) doped two-dimensional (2D) MoS 2 using ab initio calculations. The doping is achieved by substituting two or more Mo-atoms by TM-atoms of the 3d-series. Additionally, the effect of codoping on the 2D-MoS 2 by cation-cation and cation-anion pairs is also investigated. Our results demonstrate that the TM-doping of 2D-MoS 2 leads to a significant reduction of the energy gap and the appearance of magnetic features whose major characteristic is the ferromagnetic coupling of the TM-dopants. The latter is found to be significantly enhanced by codoping as demonstrated by codoping with (Co,Cu), (Ni,Cu), (Mn,Cu) and (Mn,Sb) codopant-pairs.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tunable magnetic properties of transition metal dopedMoS2

2014

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“…Although the surface of bulk TMDs has been extensively studied with STM in the past, the interpretation of the atomically resolved STM images is not straightforward. Different theoretical approaches suggest that STM images show a hexagonal pattern due to the outermost chalcogen atoms for both polarities [35][36][37][38] . However, Altibelli et al showed theoretically that the STM resolution on TMDs ultimately depends on the tip-sample distance 36 .…”

Section: Supplementary Text 1 Stm Imaging Of Monolayer Mose 2 On Bilmentioning

confidence: 99%

Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor

et al. 2014

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The remarkable properties of atomically-thin semiconducting TMD layers include an indirect-to-direct bandgap crossover 1, 2, 9 , field-induced transport with high on-off ratios 16 , 3 valley selective circular dichroism [3][4][5][6] , and strong photovoltaic response 17,18 . Fundamental understanding of the electron/hole quasiparticle band structure and many-body interactions in 2D TMDs, however, is still lacking. Enhanced Coulomb interactions due to low-dimensional effects are expected to increase the quasiparticle bandgap as well as to cause electron-hole pairs to form more strongly bound excitons [10][11][12][13] . Untangling such many-body effects in single-layer TMDs requires measurement of both the electronic bandgap and the optical bandgap, the most fundamental parameters for transport and optoelectronics, respectively. The electronic bandgap (E g ) characterizes single-particle (or quasiparticle) excitations and is defined by the sum of the energies needed to separately tunnel an electron and a hole into monolayer MoSe 2 . The optical bandgap (E opt ), on the other hand, describes the energy required to create an exciton, a correlated two-particle electron-hole pair, via optical absorption. The difference in these energies (E g -E opt ) directly yields the exciton binding energy (E b ) (Fig. 2a). Here we provide evidence for Coulomb driven quasiparticle bandgap renormalization and unusually strong exciton stability in 2D TMD through direct determination of both E g and E opt via STS and PL spectroscopy, respectively. STS and PL measurements were carried out on the same high-quality sub-monolayer MoSe 2 films grown on epitaxial bilayer graphene (BLG) on a 6H-SiC(0001) substrate.Because the MoSe 2 surface coverage for our sample was ~ 0.8 ML, we were able to simultaneously image the MoSe 2 monolayer and the underlying graphene substrate using scanning tunneling microscopy (STM). We experimentally investigated both the electronic structure and the optical transitions in monolayer MoSe 2 /BLG by combining STS and PL spectroscopy. Fig. 2b shows a typical STM dI/dV spectrum acquired on monolayer MoSe 2 /BLG. The observed electronic structure is dominated by a large electronic bandgap surrounded by features labeled V 1-4 in the valence band (VB) and C 1 in the conduction band (CB). The MoSe 2 band edges are best determined by taking the logarithm of dI/dV, as shown in Fig. 2d.There the VB maximum (VBM) for monolayer MoSe 2 is seen to be located at -1.55 ± 0.03 V and the CB minimum (CBM) at 0.63 ± 0.02 V. The relative position of E F (V bias = 0 V) with respect to the band edges reveals n-type doping for our samples, although with 5 a very low carrier concentration. We tentatively attribute the n-doping of our MoSe 2 samples to intrinsic point defects such as vacancies and/or lattice antisites, which have been found to be responsible for n-doping in similar materials 20 . Our STS measurements yield a value for the single-particle electronic bandgap of E g = E CBM -E VBM = 2.18 eV ± 0.04 eV. The uncertainty ...

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“…TMDs (M X 2 ), and in particular Monolayer MoS 2 , are known to have several different kinds of point defects, such as M and X vacancies and interstitials, impurity atoms, in addition to grain boundaries and dislocations [32][33][34][35][36][37][38][39][40] . The goal in this Section is not to give a detailed description of different defect states in TMDs, something well beyond the scope of this paper, but to capture the essential physics in a way that would enable us to obtain capture rates for electrons and holes and present the main ideas associated with the capture processes.…”

Section: E Defect Statesmentioning

confidence: 99%

Fast exciton annihilation by capture of electrons or holes by defects via Auger scattering in monolayer metal dichalcogenides

Wang¹,

Strait²,

Zhang³

et al. 2015

Phys. Rev. B

114

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The strong Coulomb interactions and the small exciton radii in two-dimensional metal dichalcogenides can result in very fast capture of electrons and holes of excitons by mid-gap defects from Auger processes. In the Auger processes considered here, an exciton is annihilated at a defect site with the capture of the electron (or the hole) by the defect and the hole (or the electron) is scattered to a high energy. In the case of excitons, the probability of finding an electron and a hole near each other is enhanced many folds compared to the case of free uncorrelated electrons and holes. Consequently, the rate of carrier capture by defects from Auger scattering for excitons in metal dichalcogenides can be 100-1000 times larger than for uncorrelated electrons and holes for carrier densities in the 10 11 -10 12 cm −2 range. We calculate the capture times of electrons and holes by defects and show that the capture times can be in the sub-picosecond to a few picoseconds range. The capture rates exhibit linear as well as quadratic dependence on the exciton density. These fast time scales agree well with the recent experimental observations and point to the importance of controlling defects in metal dichalcogenides for optoelectronic applications.

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Scanning Tunneling Microscopy Chemical Signature of Point Defects on theMoS2(0001)Surface

Cited by 111 publications

References 19 publications

Tunable magnetic properties of transition metal dopedMoS2

Tunable magnetic properties of transition metal dopedMoS2

Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor

Fast exciton annihilation by capture of electrons or holes by defects via Auger scattering in monolayer metal dichalcogenides

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