Optical Transmission through thin films.

[G01]

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.

 

[Gokul43201]

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.

 

[Dr Transport]

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.

 

[Gokul43201]

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.

 

[Redbelly98]

More like several hundred nm for wavelength of light. But of course that just reinforces your point all that much more, Gokul.

 

[G01]

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...

 

[Gokul43201]

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).

 

[gareth]

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?

 

[Dr Transport]

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.

 

[Gokul43201]

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.