Of course you can measure thickness using AFM. For this you need a step in your film. Then do the line profile scan through the step. The raise is your thickness. Please refer my paper attached.

It is imposseble or difficult to test the thickness of thin film using AFM technique.

These may give you an idea:

http://onlinelibrary.wiley.com/doi/10.1002/sia.740231202/abstract

https://en.wikipedia.org/wiki/X-ray_reflectivity

You can measure the thickness of your sample using Rutherford Backscattering Spectroscopy (RBS). You can also asses the film porosity and roughness. It can be a little difficult task, but can be done.

The problem is that RBS gives you the areal density, and the conversion to thickness depends on the film density.

Depending on the thickness you are looking at - ellipsometry or reflectometry are better. But AFM can be used if you have a reference substrate on which your coating or material is adsorbed. 

Other methods could be using Scanning Electron Microscope (SEM) and even Transmission Election Microscope (TEM) - direct observation.

However, please let us know how thin your film could be? 

Thank you all..for the valuable answers..Sir thickness of the films in micrometers as these were made by doctor blade method..How SEM and TEM can be used for thickness measurement? please explain.

Depends on sample preparation. if you cut and put upright it may be possible to measure with SEM. Using AFM - maybe only in scratch test? Believe the best method is light profilometry (interferometer) - just measure the step between layer and base w/o film. If step is lower than Z scale of your AFM system, you will be able to measure it with AFM.

Of course you can measure thickness using AFM. For this you need a step in your film. Then do the line profile scan through the step. The raise is your thickness. Please refer my paper attached.

R K Gupta is correct. Its simple to measure thickness. but you should have step on the sample so that we can calculated difference in the height. For single layer material like graphene or MoS2 we use AFM, its really accurate at nanoscale however in micron scale film i don't known about usability and accuracy.

You need to form a step. But AFM is not suitable for measuring thickness in the micron range you will broke the tip.

for SEM analysis you must orient the film surface to be paralallel the beam, in this case the measurement of the wafer thickness is possible. for TEM 

you must make a thinning of the layer

Looking at last comments it seems that my answer is not visible :)

some of the ceases it possible to measure thickness of film but film should be uniform size and thick.  

It is correct that you have to have a step in case you have to make a measurement of thickness of thin films using AFM. One can stick a cello tape on substrate before deposition and after deposition remove that tape. this would give a step which can be used to measure thickness by profilometer or by AFM.If you are using Doctor edge method, I presume you are getting self-standing thick film. In that case,  I do not know, if it would work.

Hi,

You can try to take the high distribution of two regions: substrate and substrate + film in the same substrate.

Vijayarangamuthu Kalimuthu ·sir  what does the step on the sample mean?

A step in the sample means you would have a portion of the substrate with no material on it that you can measure a linescan across using AFM. The 'step' should be as clean as you may make it, so that you get a good transition from material covered substrate to empty substrate. The average height of this 'step' over several linescans would give you an estimate of the film thickness. How you create the step depends on your deposition process. 

Usually in the films made by doctor blade, the edges are more thicker than the rest of the film. So if you only measure the height of the step, your measurement will not accurate.

My question is, does AFM able to scan over a larger area such as 5x5 mm^2  or 10x10 mm^2?

That's a really large area for an AFM scan.  Our typical scan areas (when we look for large features or steps) is 20 µm x 20 µm.

Small scan area is an inherent weakness with the AFM. If you suspect that the film edge regions may not be representative of the entire film due to crumbling, e.g., stylus profiler is a much safer bet because then one can get a macroscopic scan range.

Yes, I read this paper. It's done by so called Atomic Force Microscopy “Scratching”. See the link below:

http://www.chem.ualberta.ca/~mccreery/RLM%20publication%20PDFs/mccreery169.pdf

What is the method for performing step in a sample?

@ Jhon Burbano: FIB, scratch test.