Band Gap Formation: Bragg Reflection & Standing Waves

In summary, band gap in solids is produced at the zone boundary due to bragg reflection of the traveling wave. After reflection, it becomes a standing wave instead of a traveling wave due to the superposition of equal but opposite waves. This is possible due to the mathematical definition of a traveling wave and the effect of lattice potential at the zone boundary.
  • #1
asifmumtaz
4
0
band gap arises due to lattice potential.band gap is produced at zone boundary due to bragg reflection.there it behaves like standing wave instead of traveling wave?further formation of 2 standing waves?please help
 
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  • #2
i tried best to clear my question,
band gap in solids arises due to lattice potential.this lattice potential has max. effect at zone boundary.band gap is produced at zone boundary due to bragg reflection of traveling wave.after reflection it becomes standing wave instead of traveling wave?howz this possible?please help
 
  • #3
I'm not an expert, but I here's my opinion:

Yes, bandgap arises from the bragg reflections at the zone boundary. the traveling wave becomes a standing wave - I agree. How is this possible? The mathematical definition of traveling wave is: Amplitude * cos( k * x - omega * t), where k is the wavevector of the wave, omega is its characteristic frequency, x and t are spatial and time coordinates. When traveling wave suffers a reflection off the zone boundary there's an equal but opposite traveling wave (reflected part). By superposition then, the total k of the wave is zero - hence standing wave.
 

1. What is band gap formation?

Band gap formation refers to the creation of a range of energy levels where electrons are not able to exist within a material. This results in the material being unable to conduct electricity, making it an insulator.

2. How is band gap formation related to Bragg reflection?

Bragg reflection plays a crucial role in the formation of band gaps. When electromagnetic waves, such as light, hit a crystal lattice, they can be reflected off the lattice planes at certain angles. This results in constructive interference, which causes the formation of standing waves. These standing waves can create gaps in energy levels, leading to band gap formation.

3. What is the significance of band gap formation in materials?

The presence of a band gap in a material is important for its electrical properties. Materials with band gaps are insulators, meaning they do not conduct electricity. This can be beneficial in electronic devices where insulation is needed to prevent unwanted electrical currents.

4. Can band gap formation be controlled?

Yes, band gap formation can be controlled by manipulating the crystal structure of a material. By altering the spacing of the crystal lattice planes, the angle of Bragg reflection can be changed, resulting in different band gap sizes and positions.

5. How is band gap formation relevant in solar cells?

Solar cells rely on the conversion of light energy into electrical energy. The presence of a band gap in the material used for the solar cell is crucial for this process. The band gap allows for the absorption of specific wavelengths of light, while blocking others. This results in the creation of an electric current, making band gap formation essential for the functioning of solar cells.

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