2D Materials Introduction

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Introduction, Properties Applications of 2D
Materials

• Assad Ur Rehman

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Contents

• Introduction
• History
• Types
• Properties
• Synthesis
• Characterization
• Applications

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Introduction

• Single or Multi layered materials having
  negligible thickness (atomic scale).
• For graphene, 1 to 10 layers are treated as 2D
  Material.
• Multi layered materials are regarded as 3D
  materials when they have considerable thickness.

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History

• Bordie in 1859 made a failed attempt to exfoliate
  a single sheet from graphite.
• R.E. Peierls and L.D. Landau in 1937 suggested
  that strictly 2D material could not exist.
• Hahns-Peter Bohm introduced the term graphene in
  1962.
• Geim and Novesolov got Nobel Prize in 2004 for
  exfoliation of stable graphene and its
  characterization.

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Different Types Of 2Ds

• Graphene Single layer of Carbon.
• Germanene Single layer of Germenium.
• Silicene Single layer of Silicon.
• Phospherene Single layer of phosphorus.
• Hexa Boron Nitride Compund 2D material with
  alternating Boron and Nitrogen atoms.
• Transition Metals Dichalcogenides Compund 2D
  materials of Transition metals Chalcogens.

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Graphene

• 2D carbon allotrope having atomic dimensions with
  honeycomb structure.
• Monolayer of graphene has a thickness of 3.4 ?? .
• Nearly (97.7 per monolayer) transparent to
  visible light.
• 100 times stronger than steel (Strength 130 GPa).

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Graphene

• Highest thermal and electrical conductivity
  (mobility 2,00,000 ???? 2 /????)
• Semi Metal

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Transition Metals Di-Chalcogenides
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TMDs

• Are atomically thin semiconductors of the type
  MX2, with M transition metal atom(Mo, W etc.) and
  X a chalcogen atom (S, Se,Te) with honeycomb
  structure.
• MoS2 monolayer has a thickness of 6.5 ?? .
• MoS2 has thermal conductivity of 34.5W/mK at
  room temperature.
• 1.9eV band gap.

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Hexagonal Boron Nitride

• Has honeycomb structure of alternating Boron and
  Nitrogen atoms.
• Thermal conductivity of hBN at room temperature
  is 100-270W/mK.
• hBN is insulator having a band gap of 5-6eV.
• Atomically smooth Surface.

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Comparison Of 2D Materials
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Synthesis Techniques

• Mechanical Exfoliation

13
Synthesis Techniques

• Chemical Vapor Deposition

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Characterization

• For dimensional analysis, structural and
  electrical characterization of nano materials
  transmission electron microscopy, scanning probe
  microscopy , scanning tunneling microscopy,
  atomic force microscopy, Raman Spectroscopy and
  X-Ray Diffraction techniques are used.

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Characterization

• Transmission Electron Microscopy
• Is used for dimensional analysis (length, width,
  area) of the nano materials.

• TEM image of MoS2

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Characterization

• Atomic Force Microscopy

• AFM image of MoS2

• is one of the most accurate methods to estimate
  the number of layers of a certain nanomaterial
  because the relation between the thickness and
  number of layers of a certain nanomaterial can be
  theoretically calculated. For example, monolayer
  MoS2 is 0.65 nm, monolayer WS2 is 0.9 nm and
  monolayer BP (phosphorene) is 0.6 nm.

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Characterization

• Raman Spectroscopy

• is a powerful tool to determine the molecular
  structures of the materials. Stimulated by laser
  with suitable intensity, molecular structures
  vibrating in a certain mode absorb the
  corresponding energy from the incident photons
  and emit new photons with lower energy. The
  energy difference (or frequency shift) between
  the incident photons and newly emitted photons
  indicate the information of molecular structures.

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Raman Spectroscopy
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Applications

• Optoelectronics
• Photo voltaics
• Magnetic Field Sensors
• Filtering Membrane

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Applications
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• THANK YOU