Adsorption general

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Adsorption general

• Initial stage of growth and reaction on the
  surface
• Adsorbate-substrate interaction (adsorption site)
• - Physical or chemical
• - Reconstructive and non-reconstructive
• - Atomic or Molecular (dissociative or
  non-dissociative)
• - Reactive
• Adsorbate-adsorbate interaction
• - Random or ordered
• - 2D gas, liquid, and solid
• - 2D band formation

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Langmuir isotherm - adsorption from gas phase
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Basic Mechanism of Physisorption
cf. Point dipole vs. point dipole
E P1/r3
P2 aP1/r3
F ?/r6

• van der Waals bonding

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Physisorption potential
Physisorption distance 3 10 Å

• Physisorption energy
• 10 100 meV

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• Xe/Jellium

• Xe/metals

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Physisorption Sites

• Xe/Pd(810) physisorption on stepped surface

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Physisorption sites and lateral interaction
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Xe/Graphite -domains and domain walls
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Chemisorption
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Newns-Anderson model (wide band)
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Charge redistribution in chemisorption
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Newns-Anderson model (narrow band)
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Chemisorption and reconstruction
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Work function change
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Adsorbate-adsorbate interaction

• van der Waals attraction
• Dipole forces
• Orbital overlap
• Substrate-mediated interaction
• (electronic - Friedel oscillation
• Or elastric)

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Random or ordered adsorbate layer
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Ordering in adsorbate layer
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Adsorbate band formation
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Molecular adsorption
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Dissociative adsorption
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Dissociative adsorption - energetics