Interference fringes in Absorption spectra

In summary, the conversation is about a person who deposited TiO2 thin layers on a glass conductive substrate and observed interference fringes in the absorption spectra. They were informed that the two faces of the thin layers constitute an interference filter, which reflects certain frequencies in the transmission spectrum. They were also advised to observe reflected light at non-normal incidence to see a line spectrum that fits the transmitted lines. The person requested a document to help them with the fitting process, and was advised to look up thin film interference or interference filters.
  • #1
sounouhid
22
2
Hello every one
I deposited TiO2 thin layers on glass conductive substrate and then i took there absorption spectra.
My question is why do i see interference fringes in the absorption spectra of my samples.
 
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  • #2
Your two faces of your thin layers constitute an interference filter. The lines in the transmission spectrum will, in all probability, be frequencies that are Reflected by the filter. An interference filter need not absorb any energy. In fact, in solids, the absorption tends to have a band structure and not a line structure - which occurs in the isolated molecules in gases.
Try observing the reflected light (with non-normal incidence) and that could well give you a line spectrum (comb) that will fit the transmitted lines. (Tilting the filter will change the actual frequencies slightly)
 
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  • #3
It is possible the thin layer of ## TiO_2 ## is exhibiting the Fabry-Perot effect as well as the bulk absorption spectrum that goes with it.
 
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  • #4
Thank you all guys for responding me ,i really appreciate your help.
 
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  • #5
sophiecentaur said:
Your two faces of your thin layers constitute an interference filter. The lines in the transmission spectrum will, in all probability, be frequencies that are Reflected by the filter. An interference filter need not absorb any energy. In fact, in solids, the absorption tends to have a band structure and not a line structure - which occurs in the isolated molecules in gases.
Try observing the reflected light (with non-normal incidence) and that could well give you a line spectrum (comb) that will fit the transmitted lines. (Tilting the filter will change the actual frequencies slightly)
Can you please give me a document that help me doing that fit.
 
  • #6
sounouhid said:
Can you please give me a document that help me doing that fit.
Look up thin film interference or Interference filters for loads of sources. Pick one to suit you.
 
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  • #7
sophiecentaur said:
Your two faces of your thin layers constitute an interference filter. The lines in the transmission spectrum will, in all probability, be frequencies that are Reflected by the filter. An interference filter need not absorb any energy. In fact, in solids, the absorption tends to have a band structure and not a line structure - which occurs in the isolated molecules in gases.
Try observing the reflected light (with non-normal incidence) and that could well give you a line spectrum (comb) that will fit the transmitted lines. (Tilting the filter will change the actual frequencies slightly)
OK thank you
 

Related to Interference fringes in Absorption spectra

What is the concept of interference fringes in absorption spectra?

Interference fringes in absorption spectra is a phenomenon where two or more light waves interfere with each other, resulting in a pattern of bright and dark fringes. This occurs when light passes through a medium that absorbs certain wavelengths of light.

How do interference fringes affect absorption spectra?

Interference fringes can cause certain wavelengths of light to be cancelled out or enhanced, resulting in gaps or peaks in the absorption spectrum. This can provide valuable information about the composition and properties of the absorbing medium.

What types of materials exhibit interference fringes in absorption spectra?

Interference fringes are commonly observed in materials with thin films or layers, such as oils, soap films, and thin films of gases. They can also occur in solids with varying thicknesses or in materials with multiple layers.

What is the difference between interference fringes and absorption bands?

Interference fringes refer to the specific pattern of bright and dark bands that result from the interference of light waves. Absorption bands, on the other hand, refer to the specific wavelengths of light that are absorbed by a material. Interference fringes can affect the appearance of absorption bands, but they are not the same thing.

Are interference fringes in absorption spectra significant in practical applications?

Yes, interference fringes in absorption spectra have numerous practical applications in fields such as chemistry, physics, and materials science. They can be used to analyze the composition of materials, determine the thickness of thin films, and even identify unknown substances.

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