Exfoliated and restacked MoS2 and WS2

Ionic or neutral species? Encapsulation and ordering of hard electropositive cations

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173 Citations (Scopus)

Abstract

The relationship between charge and structure in restacked MS2 (M = Mo, W) has been probed by cation encapsulation and chemical oxidation and characterized by elemental analysis, electron diffraction, X-ray diffraction, and Differential Scanning Calorimetry. Alkali cations have been encapsulated in MoS2 and WS2 without the presence of a co-intercalated counterion, suggesting a negative charge in the 0.15-0.25 electrons per M atom range. Electron diffraction studies show ordering of these cations between the layers. Chemical oxidation with I2 or Br2 results in a change in the structure of restacked MoS2, giving rise to a √3a x √3a superlattice, whereas no change is observed in the structure of restacked WS2. Differential Scanning Calorimetry studies show that the irreversible exothermic transition to 2H-MS2 shifts to lower temperature with oxidation. The observed structural distortion and residual negative charge uniquely explain the thermopower measurements, which indicate that restacked MoS2 and WS2 are p-type metallic conductors.

Original languageEnglish
Pages (from-to)11720-11732
Number of pages13
JournalJournal of the American Chemical Society
Volume121
Issue number50
DOIs
Publication statusPublished - Dec 22 1999

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Encapsulation
Cations
Positive ions
Differential Scanning Calorimetry
Electrons
Electron diffraction
Oxidation
Differential scanning calorimetry
Thermoelectric power
Alkalies
X-Ray Diffraction
X ray diffraction
Atoms
Temperature
Chemical analysis

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "Exfoliated and restacked MoS2 and WS2: Ionic or neutral species? Encapsulation and ordering of hard electropositive cations",
abstract = "The relationship between charge and structure in restacked MS2 (M = Mo, W) has been probed by cation encapsulation and chemical oxidation and characterized by elemental analysis, electron diffraction, X-ray diffraction, and Differential Scanning Calorimetry. Alkali cations have been encapsulated in MoS2 and WS2 without the presence of a co-intercalated counterion, suggesting a negative charge in the 0.15-0.25 electrons per M atom range. Electron diffraction studies show ordering of these cations between the layers. Chemical oxidation with I2 or Br2 results in a change in the structure of restacked MoS2, giving rise to a √3a x √3a superlattice, whereas no change is observed in the structure of restacked WS2. Differential Scanning Calorimetry studies show that the irreversible exothermic transition to 2H-MS2 shifts to lower temperature with oxidation. The observed structural distortion and residual negative charge uniquely explain the thermopower measurements, which indicate that restacked MoS2 and WS2 are p-type metallic conductors.",
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T2 - Ionic or neutral species? Encapsulation and ordering of hard electropositive cations

AU - Heising, Joy

AU - Kanatzidis, Mercouri G

PY - 1999/12/22

Y1 - 1999/12/22

N2 - The relationship between charge and structure in restacked MS2 (M = Mo, W) has been probed by cation encapsulation and chemical oxidation and characterized by elemental analysis, electron diffraction, X-ray diffraction, and Differential Scanning Calorimetry. Alkali cations have been encapsulated in MoS2 and WS2 without the presence of a co-intercalated counterion, suggesting a negative charge in the 0.15-0.25 electrons per M atom range. Electron diffraction studies show ordering of these cations between the layers. Chemical oxidation with I2 or Br2 results in a change in the structure of restacked MoS2, giving rise to a √3a x √3a superlattice, whereas no change is observed in the structure of restacked WS2. Differential Scanning Calorimetry studies show that the irreversible exothermic transition to 2H-MS2 shifts to lower temperature with oxidation. The observed structural distortion and residual negative charge uniquely explain the thermopower measurements, which indicate that restacked MoS2 and WS2 are p-type metallic conductors.

AB - The relationship between charge and structure in restacked MS2 (M = Mo, W) has been probed by cation encapsulation and chemical oxidation and characterized by elemental analysis, electron diffraction, X-ray diffraction, and Differential Scanning Calorimetry. Alkali cations have been encapsulated in MoS2 and WS2 without the presence of a co-intercalated counterion, suggesting a negative charge in the 0.15-0.25 electrons per M atom range. Electron diffraction studies show ordering of these cations between the layers. Chemical oxidation with I2 or Br2 results in a change in the structure of restacked MoS2, giving rise to a √3a x √3a superlattice, whereas no change is observed in the structure of restacked WS2. Differential Scanning Calorimetry studies show that the irreversible exothermic transition to 2H-MS2 shifts to lower temperature with oxidation. The observed structural distortion and residual negative charge uniquely explain the thermopower measurements, which indicate that restacked MoS2 and WS2 are p-type metallic conductors.

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