Basic question about measurement of thin film by means of spectral reflectance

In summary, the conversation was about measuring thin film thickness using spectral reflectance. It was mentioned that if the film has a thickness less than 600 nm, but the measuring light has a wavelength larger than 600 nm, the results may not be reliable. It was also discussed that the film needs to be λ/4 thick for the light to be reflected with a maximum, with a total of λ phase shift. This information was provided by a technician.
  • #1
pyrometer
3
0
Hallo alle users,

as the title indicates, I have a question about measurement of thin film thickness by means of spectral reflectance.

Given, the to be measured thin film has thickness less than 600 nm, but the measuring light has only wavelengh larger than 600 nm. Does it mean, that the measurement results with this kind of light is not reliable for the wavelengh of the light is larger than the thickness of the to be measured film. In other words, the wavelength of measuring light should be smaller than the thickness of the to be measure film, shouldn't it?

Thanks a lot in advance!
 
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  • #2
Light will be reflected with a maximum for the first time when the film is λ/4 thick.
This gives a λ/2 path difference through the film. There is a λ/2 phase shift at the air/film interface giving a total of λ phase shift and therefore a maximum.
So the important distance is λ/4 !
 
  • #3
Thank you technician!
 

FAQ: Basic question about measurement of thin film by means of spectral reflectance

1. What is spectral reflectance?

Spectral reflectance is the measurement of the amount of light that is reflected off of a surface at different wavelengths. It can provide information about the physical properties of a material, such as its color and texture.

2. How is spectral reflectance used to measure thin films?

Spectral reflectance can be used to measure the thickness and optical properties of thin films. By analyzing the reflected light at different wavelengths, scientists can determine the thickness of the film and its refractive index, which affects how it interacts with light.

3. What is the process for measuring thin films using spectral reflectance?

The process for measuring thin films using spectral reflectance involves directing a light source at the film, which reflects the light at various wavelengths. The reflected light is then measured using a spectrometer, and the data is analyzed to determine the thickness and optical properties of the film.

4. What are the advantages of using spectral reflectance for measuring thin films?

Spectral reflectance offers several advantages for measuring thin films, including non-destructive testing, high accuracy, and the ability to measure multiple layers simultaneously. It also allows for measurements to be taken in real-time, making it useful for monitoring thin film growth and changes over time.

5. Are there any limitations to using spectral reflectance for measuring thin films?

While spectral reflectance is a powerful tool for measuring thin films, it does have some limitations. It may not be suitable for films that are highly transparent or have very low reflectance. The accuracy of the measurements can also be affected by factors such as surface roughness and the angle of incidence of the light source.

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