What do the peaks in the reflectance spectrum of silicon samples represent?

In summary, the conversation discusses the use of standard fresnel coefficients in analyzing reflectance data from silicon samples. The main question is what the peaks in the reflectivity graph represent, with the assumption that they are related to the band gap. However, it is noted that the band gap for silicon is not constant and there may be different band gaps with respect to the brillouin zone. It is suggested that the peaks correspond to peaks in the real and imaginary refractive indices, which are linked through the Kramers-Kronig relations. Further explanations or sources for understanding this concept are welcomed.
  • #1
hjelmgart
127
17
Hello,

I am currently analysing some relfectance data I obtained from measurements on several silicon samples. During the process I used the standard fresnel coefficients, and suddenly I began to wonder, what the peaks describe? The last graph at this link shows it for normal incident light, I think.

My typical approach is to relate peaks to the band gap, but then I remembered silicon has a band gap of 1,1 eV.

So what explains the peaks? I am still thinking, that it is related to the band gap. But the band gap isn't constant either? The 1,1 eV is just the lowest gap, right?

So do the peaks represent different band gaps with respect to the brillouin zone, or how is it?

Any suggestions or explanations appreciated! Or possibly a source, that explains it, as I so far had no luck at finding such.
 
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  • #2
One reflectivity peak is due to a peak in the real refractive index, the other is due to a peak in the imaginary refractive index: and that the formula for calculating reflectivity applies for real- and complex-valued refractive indices.

Note too, that the real and imaginary refractive index components are linked via the Kramers-Kronig relations.

Claude.
 

What is a reflectance spectrum?

A reflectance spectrum is a graph that shows the amount of light reflected by a substance at different wavelengths. It is used to identify the unique spectral signature of a substance, which can provide information about its composition and properties.

What are "peaks" in a reflectance spectrum?

Peaks in a reflectance spectrum refer to the points on the graph where the reflectance values are highest. These peaks can indicate the presence of specific substances or materials that have a strong reflectance at certain wavelengths.

How are reflectance spectra measured?

Reflectance spectra are typically measured using a spectrophotometer, which shines a light of a specific wavelength onto a sample and measures the amount of light that is reflected. The data is then plotted on a graph to create the reflectance spectrum.

What can we learn from studying peaks in a reflectance spectrum?

Studying peaks in a reflectance spectrum can provide valuable information about the composition and properties of a substance. For example, the location and intensity of peaks can help identify the presence of specific chemical bonds or elements in a material.

How are reflectance spectra used in scientific research?

Reflectance spectra are widely used in various fields of scientific research, such as geology, chemistry, and remote sensing. They can help identify and characterize different substances, monitor changes in the environment, and provide insights into the physical and chemical properties of materials.

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