Sara, we have micro-EDXRF instrumentation able to measure thin layers thickness and also to do mapping of thickness along an area, let say homogeneity at millimeter to cemtimeters scale. This is based on measuring the X-ray emmission energy of an chemical element in the layer (Sn in your case) or the depletion of X-ray energy of one element in the substrate, caused by the overlying layer. If you can send some sample I can try to do measurements in my lab.
Good luck with your research!!!
You can convert your absorption spectrum to transmission. The film thickness can be calculated from the
transmission interference fringes, where you can use your n, and k parameters, you can revise this paper.
Generally yes. The absorbance of a phase (liquid, gas, solid) can be related to the light path i.e. the thickness. But to be able to apply Lambert-Beer's law, you would need to know the molar extinction coefficient of your thin-film material.
The paper provided by Claudio is a good one. I also like papers by R. Swanepole that also measure thin films in transmission. One of the papers also comments on including scattering in addition to refractive index and absorption. this can be seen as a dampening of the interference fringes. It is somewhat important to consider the dispersion of N as a function of wavelength, then you will get better answers. With the metal oxides you may also run into some issues of the band edge being dependent on the conductivity of the film, and for very conductive films you may also see an effect of the free carrier absorption. A very precise way to measure thickness (and n) is by prism coupling, but that can be a little tedious to set up. It should work in your case, since I assume the SnO2 film will have a higher index than the substrate. The films does need to be thick enough to support more than one mode. i.e. more than one fringe in transmission.
You should maybe consider doing Nullellipsometry or Spectroscopic Ellipsometry. Ellipsometry determines the change of the polarization of light upon reflection of interfaces.
Queralt I, Ibañez J., Marguí E. and Pujol J., Thickness measurement of semiconductor thin films by energydispersive X-ray fluorescence benchtop instrumentation: Application to GaN epilayers grown by molecular
beam epitaxy. Spectrochimica Acta Part B, 65:583:586, 2010
Dear Mr Claudio Gutiérrez Lazos
is there any limit on minimum thickness, in method that you suggest? my film's thickness is about 200nm or less, and I have absorption and transmission data in the wavelength range of 300 to 1100 nm.
Optical methods have difficulties in sub-micron ranges. I suggest the use of EDXRF with limits of thickness determination around few nanometers
thank you so much Mr ignasi queralt
EDXRF seems good method, but unfortunately we don't have needed equipment now.
Around 200 nm can be easily measured by transmittance data.from n-k relation..transmittance pattern should be wavy type..otherwise cut your film and take cross section of the film by FESEM. it will more accurate
Dear Sara, considering that you need an interference pattern in order to apply Swanepoel method, as Ignasi commented, is a problem in ultrahin films that oscillations are not presented. In your case, I agree with Christian, you can use ellypsometry.
Sara, we have micro-EDXRF instrumentation able to measure thin layers thickness and also to do mapping of thickness along an area, let say homogeneity at millimeter to cemtimeters scale. This is based on measuring the X-ray emmission energy of an chemical element in the layer (Sn in your case) or the depletion of X-ray energy of one element in the substrate, caused by the overlying layer. If you can send some sample I can try to do measurements in my lab.
Good luck with your research!!!
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