Why amorphous phase materials have wider bandgap?

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Discussion Overview

The discussion centers around the reasons why amorphous phase materials are believed to have wider bandgaps compared to their crystalline counterparts. Participants explore theoretical explanations and potential mechanisms behind this phenomenon, touching on concepts from solid-state physics.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that the bonding mechanism remains unchanged during the transition from crystalline to amorphous phases, yet the bandgap increases.
  • One participant suggests that the periodic Bloch wave-functions in crystalline materials do not account for forbidden energy levels as effectively as in amorphous materials, potentially leading to a wider bandgap.
  • Another participant mentions the need for perturbation theory in understanding the bandgap differences.
  • There is a suggestion to explore concepts like "Anderson localization" and "band edge states" as they may relate to the bandgap characteristics of amorphous materials.
  • One participant questions the assertion that amorphous materials have wider bandgaps, arguing that they might actually have narrower bandgaps due to band edge tailing effects.

Areas of Agreement / Disagreement

Participants express differing views on whether amorphous materials indeed have wider bandgaps, with some supporting this idea while others contest it, indicating that the discussion remains unresolved.

Contextual Notes

Participants reference various theoretical concepts and effects, but there are no consensus definitions or resolutions regarding the assumptions about bandgap behavior in amorphous versus crystalline materials.

sttan
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I'm wondering why the amorphous phase materials have wider bandgap compared to its crystalline phase. To my best knowledge, the bonding mechanism does not changed as the material transform from crystalline phase to amorphous phase. So what causes it has larger bandgap?

ST
 
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sttan said:
I'm wondering why the amorphous phase materials have wider bandgap compared to its crystalline phase. To my best knowledge, the bonding mechanism does not changed as the material transform from crystalline phase to amorphous phase. So what causes it has larger bandgap?

ST


I think (not to sure though) it has something to do with the fact that the periodic Bloch wave-functions do not account for the forbidden energy as much as they used to in a cristal-lattice.

The band gap is there because the electrons can acquire two different potential energy-values when passing through the periodic potential of the positive lattice ions

regards
marlon
 
Look at:
http://www.wordiq.com/definition/Solid_state_physics

perturbation theory is needed.
 
Last edited by a moderator:
Thanks to Marlon and Kurious...

ST
 
Search for "Anderson localization" and "band edge states".
 
sttan said:
I'm wondering why the amorphous phase materials have wider bandgap compared to its crystalline phase. To my best knowledge, the bonding mechanism does not changed as the material transform from crystalline phase to amorphous phase. So what causes it has larger bandgap?

ST

Are you sure amorphous materials have wider bandgap? I think they should have narrower Eg due to the band edge tailing effect.
 

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