Influence of rhenium on the structural and optical properties of molybdenum disulfide

Sigiro, Mula; Huang, Ying-Sheng; Ho, Ching‐Hwa; Lin, Yung‐Chang; Suenaga, Kazu

doi:10.7567/jjap.54.04dh05

Cited by 22 publications

(12 citation statements)

References 41 publications

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“…It is worth noting that similar spectral features have been observed for MoS 2 and WS 2 in piezoreflectance spectra343536 where the authors have attributed this signal to an excited state of A exciton transition. However recent PR studies of MoS 2 crystals suggest that this resonance is associated with a direct optical transition at H point of Brillouin zone31, see the Brillouin zone in Fig.…”

Section: Resultssupporting

confidence: 70%

Pressure coefficients for direct optical transitions in MoS2, MoSe2, WS2, and WSe2 crystals and semiconductor to metal transitions

Dybała

Polak

Kopaczek

et al. 2016

Sci Rep

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The electronic band structure of MoS2, MoSe2, WS2, and WSe2, crystals has been studied at various hydrostatic pressures experimentally by photoreflectance (PR) spectroscopy and theoretically within the density functional theory (DFT). In the PR spectra direct optical transitions (A and B) have been clearly observed and pressure coefficients have been determined for these transitions to be: αA = 2.0 ± 0.1 and αB = 3.6 ± 0.1 meV/kbar for MoS2, αA = 2.3 ± 0.1 and αB = 4.0 ± 0.1 meV/kbar for MoSe2, αA = 2.6 ± 0.1 and αB = 4.1 ± 0.1 meV/kbar for WS2, αA = 3.4 ± 0.1 and αB = 5.0 ± 0.5 meV/kbar for WSe2. It has been found that these coefficients are in an excellent agreement with theoretical predictions. In addition, a comparative study of different computational DFT approaches has been performed and analyzed. For indirect gap the pressure coefficient have been determined theoretically to be −7.9, −5.51, −6.11, and −3.79, meV/kbar for MoS2, MoSe2, WS2, and WSe2, respectively. The negative values of this coefficients imply a narrowing of the fundamental band gap with the increase in hydrostatic pressure and a semiconductor to metal transition for MoS2, MoSe2, WS2, and WSe2, crystals at around 140, 180, 190, and 240 kbar, respectively.

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Section: Resultssupporting

confidence: 70%

Pressure coefficients for direct optical transitions in MoS2, MoSe2, WS2, and WSe2 crystals and semiconductor to metal transitions

Dybała

Polak

Kopaczek

et al. 2016

Sci Rep

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“…For example, in the case of changing stacking structure, rhenium-doped WS 2 and MoS 2 could render the layered compounds transformed from the two-layer hexagonal (2H) phase into the three-layer rhombohedral (3R) phase. The structure change also reduces the transition energies of A and B excitons near the band edge. , The Nb dopant induced inside the layered WSe 2 significantly reduced the potential barrier height of the W x Nb 1– x Se 2 interfacial regions and could also improve the device performance in a WSe 2 -based field-effect transistor . In addition, the rare-earth Er-doped MoS 2 nanosheet can be an infrared (IR) emitter of 1.55 μm for fiber communication use …”

Section: Introductionmentioning

confidence: 99%

Effect of Cr on the Structure and Property of Mo_1–xCr_xSe₂ (0 ≤ x ≤ 0.2) and Cr₂Se₃

Lai

2019

ACS Appl. Electron. Mater.

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Layered Mo 1−x Cr x Se 2 (0 ≤ x ≤ 0.2) and Cr 2 Se 3 single crystals are grown by a chemical vapor transport method using I 2 as a transport agent. X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses show that the Cr-doped MoSe 2 is maintained in a two-layer hexagonal (2H) structure like that of undoped MoSe 2 , whereas Cr 2 Se 3 is crystallized in the rhombohedral (hexagonal) phase. Lattice constants of the layered Mo 1−x Cr x Se 2 (0 ≤ x ≤ 0.2) series are increased as the Cr content is increased. The direct and indirect bandgaps are also decreased with increasing Cr composition in Mo 1−x Cr x Se 2 (0 ≤ x ≤ 0.2). X-ray photoemission spectroscopy (XPS) revealed the Mo site (valence Mo 4+ ) substituted by Cr in the Mo 1−x Cr x Se 2 (0 < x ≤ 0.2) series mainly causes a Cr 6+ valence state and produces n-type conductivity. For Cr 2 Se 3 , the main state is Cr 3+ . Resistivity, Hall, and hot-probe measurements show high p-type conductivity of Cr 2 Se 3 . Temperature variations of magnetic susceptibility show that an antiferromagnetic transition occurred in Cr 2 Se 3 below and close to 50 K. The photocatalytic behavior of the layered Mo 1−x Cr x Se 2 (0 ≤ x ≤ 0.2) series has also been assessed by methylene-blue (MB) degradation. The degradation efficiency increases as the Cr content is increased. The photocatalysis enhancement (with increasing Cr) is due to bandgap reduction and ionic contribution from the largely Cr 6+ state. The Cr 2 Se 3 and Cr-doped MoSe 2 can be applied to magnetic and photocatalytic materials.

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“…So far, CER spectroscopy has never been applied to study TMDs but PzR spectroscopy was widely applied to study bulk TMDs. [20][21][22][23][24] However, optical transitions at the H point of Brillouin zone have not been identified in these spectra. It means that the issue of optical transitions at the H point of Brillouin zone is an open question for bulk TMDs, especially that this issue has never been considered for TMDs other than MoS 2 (i.e., MoSe 2 , WS 2 , and WSe 2 ).…”

Section: Introductionmentioning

confidence: 99%

Direct optical transitions at K- and H-point of Brillouin zone in bulk MoS2, MoSe2, WS2, and WSe2

Kopaczek

Polak

Scharoch

et al. 2016

Journal of Applied Physics

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Modulated reflectance (contactless electroreflectance (CER), photoreflectance (PR), and piezoreflectance (PzR)) has been applied to study direct optical transitions in bulk MoS2, MoSe2, WS2, and WSe2. In order to interpret optical transitions observed in CER, PR, and PzR spectra, the electronic band structure for the four crystals has been calculated from the first principles within the density functional theory for various points of Brillouin zone including K and H points. It is clearly shown that the electronic band structure at H point of Brillouin zone is very symmetric and similar to the electronic band structure at K point, and therefore, direct optical transitions at H point should be expected in modulated reflectance spectra besides the direct optical transitions at the K point of Brillouin zone. This prediction is confirmed by experimental studies of the electronic band structure of MoS2, MoSe2, WS2, and WSe2 crystals by CER, PR, and PzR spectroscopy, i.e., techniques which are very sensitive to critical points of Brillouin zone. For the four crystals besides the A transition at K point, an AH transition at H point has been observed in CER, PR, and PzR spectra a few tens of meV above the A transition. The spectral difference between A and AH transition has been found to be in a very good agreement with theoretical predictions. The second transition at the H point of Brillouin zone (BH transition) overlaps spectrally with the B transition at K point because of small energy differences in the valence (conduction) band positions at H and K points. Therefore, an extra resonance which could be related to the BH transition is not resolved in modulated reflectance spectra at room temperature for the four crystals.

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Influence of rhenium on the structural and optical properties of molybdenum disulfide

Cited by 22 publications

References 41 publications

Pressure coefficients for direct optical transitions in MoS2, MoSe2, WS2, and WSe2 crystals and semiconductor to metal transitions

Pressure coefficients for direct optical transitions in MoS2, MoSe2, WS2, and WSe2 crystals and semiconductor to metal transitions

Effect of Cr on the Structure and Property of Mo_1–xCr_xSe₂ (0 ≤ x ≤ 0.2) and Cr₂Se₃

Direct optical transitions at K- and H-point of Brillouin zone in bulk MoS2, MoSe2, WS2, and WSe2

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Influence of rhenium on the structural and optical properties of molybdenum disulfide

Cited by 22 publications

References 41 publications

Pressure coefficients for direct optical transitions in MoS2, MoSe2, WS2, and WSe2 crystals and semiconductor to metal transitions

Pressure coefficients for direct optical transitions in MoS2, MoSe2, WS2, and WSe2 crystals and semiconductor to metal transitions

Effect of Cr on the Structure and Property of Mo1–xCrxSe2 (0 ≤ x ≤ 0.2) and Cr2Se3

Direct optical transitions at K- and H-point of Brillouin zone in bulk MoS2, MoSe2, WS2, and WSe2

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Effect of Cr on the Structure and Property of Mo_1–xCr_xSe₂ (0 ≤ x ≤ 0.2) and Cr₂Se₃