Growth And Self-Assembly at TU München | Flashcards & Summaries

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Lernmaterialien für Growth and Self-Assembly an der TU München

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What does Epitaxy mean?

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Method to deposit a single-crystalline film on a single-crystalline substrate

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How can Impurity Scattering be reduced?

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Example: single modulation doped AlGaAs/GaAs 2DEG 

scattering strongly suppressed by spatial separation of ionized dopants and free electron gas

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elementary growth process

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1. Adsorption of constituent atoms/molecules

2. Surface migration and dissociation 

3. Incorporation of atoms into crystal lattice 

4. Thermal desorption of atoms/molecules not incorporated

Lösung ausblenden
TESTE DEIN WISSEN

SK growth results naturally in self-assembled QDs with mostly random positioning on the growth surface. There are, however, ways to induce lateral arrangement for better position control. Which features can lead to lateral arrangement? (4 answers) 


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Growth on step-terrace surfaces

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Self-Organization vs. Lithography

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  • spontaneous formation of spatial, temporal or Spatio-temporal pattern of individual constituents
  • formation of quantum heterostructures (combination of different semiconductors)
  • new quantum physical properties -> new quantum devices
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Which of the following characteristics describes metal-organic vapor phase epitaxy (MOVPE)?

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low-temperature growth / low growth rate / low-to-atmospheric pressure

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What is size-limited growth influenced by?

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thermodynamic theories suggest

  • there exist an optimum island size that minimizes the energy of the system 

kinetic theories suggest

  • Ostwald ripening: thermodynamic tendency towards ripening (growth of large islands at the expense of small ones)… 
  • but under normal experimental conditions ripening occurs to slowly to be observed
Lösung ausblenden
TESTE DEIN WISSEN

elementary growth process

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1. formation of sub-critical nuclei

2. become critical nuclei, stable 2D or 3D island growth

3. Islanding and Coalescence, Growth

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Molecular Beam Epitaxy

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growth in Ultra High Vacuum (UHV) with 3 stage UHV system: load-loc, transfer chamber, growth chamber

• Low growth rates (< 1 ML/sec)
• Low source consumption
• Low growth temperatures due to absence of chemical species (~550 °C GaAs, ~700 °C GaN,…)
• typically H–free beam fluxes
• very precise control of surface composition and morphology
• in situ control of crystal growth at atomic level (RHEED,..)
• disadvantage: low throughput (limits for industrial applications)

Lösung ausblenden
TESTE DEIN WISSEN

How does RHEED word?

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TESTE DEIN WISSEN
  • high energy electron beam comes in with an increasing angle of incidence interacting with the crystalline lattice 
  • diffraction contains information of crystalline properties of the sample surface
Lösung ausblenden
TESTE DEIN WISSEN

What are the goals of Metal-Organic Vapor Phase Epitaxy (MOVEPE)?

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TESTE DEIN WISSEN
  • homogeneity
  • thickness and carrier profile across substrate
Lösung ausblenden
TESTE DEIN WISSEN

How can one make use of the elastic dipole-dipole interactions between islands in dense systems?

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TESTE DEIN WISSEN
  • the interaction energy changes sign depending on m
  • m - unit vector in surface plane parallel to direction between islands
  • attraction between islands withtin certain range of direction m close to elastically soft directions [100] or [010] 

Artificial Arrangement of Islands - Laterally

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Q:

What does Epitaxy mean?

A:

Method to deposit a single-crystalline film on a single-crystalline substrate

Q:

How can Impurity Scattering be reduced?

A:

Example: single modulation doped AlGaAs/GaAs 2DEG 

scattering strongly suppressed by spatial separation of ionized dopants and free electron gas

Q:

elementary growth process

A:

1. Adsorption of constituent atoms/molecules

2. Surface migration and dissociation 

3. Incorporation of atoms into crystal lattice 

4. Thermal desorption of atoms/molecules not incorporated

Q:

SK growth results naturally in self-assembled QDs with mostly random positioning on the growth surface. There are, however, ways to induce lateral arrangement for better position control. Which features can lead to lateral arrangement? (4 answers) 


A:

Growth on step-terrace surfaces

Q:

Self-Organization vs. Lithography

A:
  • spontaneous formation of spatial, temporal or Spatio-temporal pattern of individual constituents
  • formation of quantum heterostructures (combination of different semiconductors)
  • new quantum physical properties -> new quantum devices
Mehr Karteikarten anzeigen
Q:

Which of the following characteristics describes metal-organic vapor phase epitaxy (MOVPE)?

A:

low-temperature growth / low growth rate / low-to-atmospheric pressure

Q:

What is size-limited growth influenced by?

A:

thermodynamic theories suggest

  • there exist an optimum island size that minimizes the energy of the system 

kinetic theories suggest

  • Ostwald ripening: thermodynamic tendency towards ripening (growth of large islands at the expense of small ones)… 
  • but under normal experimental conditions ripening occurs to slowly to be observed
Q:

elementary growth process

A:

1. formation of sub-critical nuclei

2. become critical nuclei, stable 2D or 3D island growth

3. Islanding and Coalescence, Growth

Q:

Molecular Beam Epitaxy

A:

growth in Ultra High Vacuum (UHV) with 3 stage UHV system: load-loc, transfer chamber, growth chamber

• Low growth rates (< 1 ML/sec)
• Low source consumption
• Low growth temperatures due to absence of chemical species (~550 °C GaAs, ~700 °C GaN,…)
• typically H–free beam fluxes
• very precise control of surface composition and morphology
• in situ control of crystal growth at atomic level (RHEED,..)
• disadvantage: low throughput (limits for industrial applications)

Q:

How does RHEED word?

A:
  • high energy electron beam comes in with an increasing angle of incidence interacting with the crystalline lattice 
  • diffraction contains information of crystalline properties of the sample surface
Q:

What are the goals of Metal-Organic Vapor Phase Epitaxy (MOVEPE)?

A:
  • homogeneity
  • thickness and carrier profile across substrate
Q:

How can one make use of the elastic dipole-dipole interactions between islands in dense systems?

A:
  • the interaction energy changes sign depending on m
  • m - unit vector in surface plane parallel to direction between islands
  • attraction between islands withtin certain range of direction m close to elastically soft directions [100] or [010] 

Artificial Arrangement of Islands - Laterally

Growth and Self-Assembly

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