High and low energy photon absorption

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SUMMARY

Mono C-silicon, when cooled with helium, can absorb high-intensity lasers in the wavelength range of 900-1100 nm, although some infrared absorption is expected. Silicon exhibits transparency for photon energies below the indirect band gap of Eg=1.1 eV at room temperature, allowing light to pass through without significant absorption. The increase in material temperatures due to ultraviolet and visible light occurs through the same mechanism as any light, where absorption leads to thermal excitation. At low temperatures, the larger direct bandgap influences absorption characteristics.

PREREQUISITES
  • Understanding of Mono C-silicon properties
  • Knowledge of photon energy and band gap concepts
  • Familiarity with thermal effects in semiconductor materials
  • Basic principles of light absorption and transmission
NEXT STEPS
  • Research the absorption characteristics of silicon at various temperatures
  • Learn about the implications of direct and indirect band gaps in semiconductors
  • Explore the effects of different wavelengths on material heating
  • Investigate helium cooling techniques for semiconductor applications
USEFUL FOR

Materials scientists, semiconductor engineers, and physicists interested in photon absorption properties and thermal effects in silicon-based materials.

Karim Habashy
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Hi All,

Kindly find here 2 questions, i was wondering about:

1) Will (helium cooled) Mono C-silicon be able to absorb a high intensity laser of about 900-1100 nm ?

2) How can Ultra-violet and visible light cause rise in material temperatures.

Thanks.
 
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1. That would be IR so it would be surprising if some was not abdorbed.
2. Same way any light increases temperature.
 
Silicon is quite transparent at photon energies below the indirect band gap of Eg=1.1 eV at room temperature.
It is an amazing experience to look straight trough a wafer with night vision.
There is absorption below Eg because the valence band is not fully occupied due to thermal effects.
Above Eg phonon assisted transitions occur.
At very low T it is the larger direct bandgap that determines absorption.
Anything at or below red light passes through.
See http://en.wikipedia.org/wiki/Direct_and_indirect_band_gaps#Implications_for_light_absorption
See also
http://refractiveindex.info/?shelf=main&book=Si&page=Vuye-20C
 

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