There are several methods, mostly optical ones that use transmittance spectra to model the data and extract the parameters including thin film thickness. Swanepoel method is very popular but it is limited to the cases with interference pattern. Pointwise unconstrained minimization algorithm is more effective. It is prepared in a way that you can model both R and T or combined even without any interference fringes.

Quality and accuracy of thickness measured by ellipsometric techniques is dependent on the type of substrate, roughness etc.. which substrate did you use? Read this paper: DOI: 10.1021/jp802173m

[i] Determine k; the extinction coefficient by applying :

k= α λ/4π

[ii] Then find α; the optical absorption coefficient as :

α = (h. ν -Eg) ^1/2.

Eg is the band gap.

[iii] Lastly, find the thickness (t) by the relation:

α. = 2.303A/t.

You can also use x-ray reflectivity, which is very accurate

Thanks !!!!! for your quick response @ Ali A. Ziabari & @ Sridhar Vadahanmbi

I Have prepared Graphene oxide thin film on glass slide. Which model is best suited in this case ?

Dear Hans-Ulrich Krebs;

Can you give us more detail for your X-ray reflectivity method.

Thanks !!!!!! @ Hans-Ulrich Krebs @ for this suggestion, Please send me some material regarding this X-ray reflectivity on my email- [email protected]

Spectroscopic ellipsometry spectra can be modelled using general transfer matrix technique, provided that the dielectric functions of each layer in the layered structure are known. M. Schubert has published a lot of papers and several books discuss the modelling technique of SE spectra and analysis of SE spectra to extract material information including layer thickness.

Dear Shantilal,

I recommend if you are in the visible regime that you use a classical Lorentz oscillator model to simulate the dielectric constant of graphen oxide. You should have this model in the software of your ellipsometer.

Approach 1 : First try with a plain layer made by a lorentz model

Approach 2 : It the the thickness is not physically acceptable, you can had a second layer at the top of the first one which is constituted by 50% of air ( n=1) and 50% of oxide. This second layer will simulate the roughness of your sample.

You can have a look to this publication :

Optical investigation of reduced graphene oxide by spectroscopic ellipsometry and the band-gap tuning Y. Shen1,2, P. Zhou1,a), Q. Q. Sun1,b), L. Wan3, J. Li3, L. Y. Chen2, D. W. Zhang1 and X. B. Wang3,c) Appl. Phys. Lett. 99, 141911 (2011);

Best wishes

Eric

Thanks !!!!! @ Eric Finot @ & @ Sai Cheong Lee @ for your valuable suggestions.

Im not sure how thick these layers are normaly. But for other thin films i had quite good result in cutting the sample, sputtering gold on it (really thin like 2-5nm) and then put the edge into a SEM. For layers wuth 10nm thickness and more, that seemed to be the most accurate method for me, althou i must admit graphene layers usually are thinner than one nm and thus may not be observable by this method.

I think simulation is better and give accurate in some times at below 15nm

Film thickness can be measured by:

- A profilometer

- Variable Angle Spectroscopic Ellipsometry (VASE)

- UV-Visible Spectroscopy

- Scanning electron microscope (SEM)

- Atomic force microscopy (AFM)

I think AFM is the best method for you to measure the film thickness. It is the height difference between the glass slide and the graphene oxide.

1- SEM imaging tranching

2- See Pub: Structural,opto-thermal and electrical properties of

ZnO:Mo sprayed thin films, Materials Science in Semiconductor Processing 15(2012)282–292

Hello everybody .....!!!! Thanks !!!! @ for valuable discussion.

Maybe you have some sort of microstructured graphene oxid layer, which you can determine by imaging ellipsometry.

Best regards

Christian