Optical Transmission through thin films.

In summary, the conversation discusses the issue of determining the thickness of a 1nm Ni coating on zirconium. The person does not have access to an AFM and is seeking alternative methods, such as using light transmission data or finding data tables with information on optical transmission vs. thickness. Suggestions are made to use a thermal/e-beam evaporator or to illuminate the sample with a laser to observe interference fringes. However, due to the small thickness of the film, these methods may not be accurate. Another person shares their experience with using a transmission/reflection technique and mentions the possibility of surface adsorbates affecting the results. The conversation ends with someone expressing interest in the AFM technique for measuring film thickness.
  • #1
G01
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Hello everyone.

I have some zirconium that is coated with 1nm of Ni. Now, here's the problem: I don't know if the coating is actually 1nm and have to find out. I don't have access to our AFM today, so I can't use that. But I do have light transmission data from the sample. i.e. I know the percentage of light the coating transmits and the percentage reflected. If there any way I can use this to find the thickness of the metal film. Are there data tables somewhere that have information, such as optical transmission vs. thickness or something like that? Any help finding this information would be greatly appreciated.
 
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  • #2
When you say you know the transmission coefficient, do you mean that you know it as a function of wavelength? Over what window? Anyway, at 1nm, I doubt you'll get anything useful out of a reflectance spectrum.

If you have access to a thermal/e-beam evaporator, you may be able to work with the thickness monitor - but for that, you'll first need the substrate without the film.
 
  • #3
Do you know the thickness of the zirconium? From the two reflection spectra and the transmission spectrum, you should be able to find the thickness. Even better, illuminate with a laser and see the interference spectrum at off normal incidence, the spacing of the fringes will guide you in determining th ethickness.
 
  • #4
Dr Transport said:
Even better, illuminate with a laser and see the interference spectrum at off normal incidence, the spacing of the fringes will guide you in determining th ethickness.
Will not work - there will be no fringes. Thickness of film = 1nm, wavelength of light = several nm.
 
  • #5
More like several hundred nm for wavelength of light. But of course that just reinforces your point all that much more, Gokul.
 
  • #6
Thanks for the advice guys! I'm think I may have found some data on google for %T vs. wavelength for different thicknesses, but all the data points are thicker than my films. Maybe I can plug some values for the wavelength I care about into excel and fit a function to them. Then I could use the function to predict my films thickness...
 
  • #7
G01 said:
Thanks for the advice guys! I'm think I may have found some data on google for %T vs. wavelength for different thicknesses, but all the data points are thicker than my films. Maybe I can plug some values for the wavelength I care about into excel and fit a function to them. Then I could use the function to predict my films thickness...
Methinks, more than anything else, you attempt will be foiled by your error bars (i.e., that 1nm as well as 0nm will lie within the error bar).
 
  • #8
I have had a very similar problem to this, I needed to varify thickness of thin Ni films on an Al203 substrate. The films are of the order you mentioned, I tried using a the transmission/reflection technique (F20 instrument by Filmetrics) but they tell me the films are really too thin for this. However I did get results within the region of the films but they all seemed much thicker, this was possibly due to surface adsorbates which I am am keen to measure the thickness of.

I'm interested in the AFM technique you mentioned, how does this work? I know what an AFM is, but how can you get it to determine film thicknesses?
 
  • #9
Gokul43201 said:
Will not work - there will be no fringes. Thickness of film = 1nm, wavelength of light = several nm.

What was I thinking?, I been working as a program manager too long, time to get back to doing real science.
 
  • #10
gareth said:
I'm interested in the AFM technique you mentioned, how does this work? I know what an AFM is, but how can you get it to determine film thicknesses?
Put sample on its side - cleave/cut - image.
 

Related to Optical Transmission through thin films.

1. What is "Optical Transmission through thin films"?

"Optical Transmission through thin films" refers to the phenomenon where light passes through a thin layer of material, such as a thin film coating, and is either transmitted or absorbed by the material. This process is important in various applications such as optical coatings, solar cells, and optical sensors.

2. How does the thickness of the thin film affect optical transmission?

The thickness of the thin film plays a crucial role in determining the amount of light that is transmitted through it. As the film thickness increases, the amount of light transmitted decreases due to increased absorption and scattering within the film. This relationship is described by the Beer-Lambert law.

3. What factors influence the optical transmission of thin films?

Several factors can affect the optical transmission of thin films, including the thickness of the film, the refractive index of the film material, the angle of incidence of the light, and the wavelength of the light. The properties of the substrate and the surrounding medium can also have an impact on the transmission.

4. How is optical transmission through thin films measured?

Optical transmission through thin films can be measured using various techniques, such as spectrophotometry, ellipsometry, and interferometry. These methods involve measuring the intensity of light that passes through the film at different wavelengths and angles of incidence to determine the film's optical properties.

5. What are some practical applications of understanding optical transmission through thin films?

Understanding and controlling optical transmission through thin films is essential in various fields, such as optics, electronics, and energy conversion. Thin film coatings are used to enhance the performance of optical devices, such as lenses and mirrors, and to create anti-reflective surfaces. Thin films are also crucial in the development of solar cells and optical sensors for detecting various environmental parameters.

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