"The basic principle of this multiple beam interferometer is as follows: a thin transparent glass slide is put onto a highly reflecting surface. The glass slide is tilted against the surface by an angle α. If this set-up is illuminated by monochromatic light, multiple beam interferences lead to the formation of equidistant interference lines. The more partial beams interfere, the sharper the lines. Their distance depends on α. A film thickness can be determined by this method as follows: First a schratch is made into the film which reaches down to the substrate (it is also possible to mask a part of the substrate during deposition which leads to the formation of a step). Then the sample is coated by a highly reflective layer. Because of the scratch the distance reflector/interference slide is changed, which leads to an offset of the interference lines relative to each other. The film thickness d is given by d=∆N*(λ/2) where ∆N is the number (or the part) of the lines by which the interference lines are shifted by the scratch or the step." See the attached link (p.87) on very many different ways to measure the film thickness. According to that manual, the Tolansky method is not necessarily the best one because "the advantage of fast and easy use is counteracted by the disadvantage that a suitable scratch or step has to be present. In addition the step (scratch) has to be covered by a highly reflective coating, mostly Ag. The resolution lies at approx. ± 1 nm if one works with strictly monochromatic light and highly reflactive samples and interference slides".

http://sxs.ifp.tuwien.ac.at/forschung/duenne_schichten/pdf/t_p_ds_chapter4.pdf

"The basic principle of this multiple beam interferometer is as follows: a thin transparent glass slide is put onto a highly reflecting surface. The glass slide is tilted against the surface by an angle α. If this set-up is illuminated by monochromatic light, multiple beam interferences lead to the formation of equidistant interference lines. The more partial beams interfere, the sharper the lines. Their distance depends on α. A film thickness can be determined by this method as follows: First a schratch is made into the film which reaches down to the substrate (it is also possible to mask a part of the substrate during deposition which leads to the formation of a step). Then the sample is coated by a highly reflective layer. Because of the scratch the distance reflector/interference slide is changed, which leads to an offset of the interference lines relative to each other. The film thickness d is given by d=∆N*(λ/2) where ∆N is the number (or the part) of the lines by which the interference lines are shifted by the scratch or the step." See the attached link (p.87) on very many different ways to measure the film thickness. According to that manual, the Tolansky method is not necessarily the best one because "the advantage of fast and easy use is counteracted by the disadvantage that a suitable scratch or step has to be present. In addition the step (scratch) has to be covered by a highly reflective coating, mostly Ag. The resolution lies at approx. ± 1 nm if one works with strictly monochromatic light and highly reflactive samples and interference slides".

http://sxs.ifp.tuwien.ac.at/forschung/duenne_schichten/pdf/t_p_ds_chapter4.pdf

@ Sergei- thanks a lot.. but I'm new to this field i dont know how to set it up in lab. i need a practical guidance explaining what all components i need and also how i go about setting it up.

Dear Venkatesh, I would recomment the book from Tolansky himself - couldn't you get it somewhere in a library?

Multiple Beam Interference Microscopy of Metals

Samuel Tolansky

Academic Press, 1970

Check http://www.worldcat.org/title/multiple-beam-interference-microscopy-of-metals/oclc/249847541

to find it in a library. Or to download it somewhere?

Here is a link from Dusseldorf University, the text is in german however:

http://www.anphy.uni-duesseldorf.de/ag_getzlaff/Veranstaltungen/F_Praktikum/fp_ap03.pdf

I may contact my old colleagues whether or not they have some information about their setup! I will come back on this!

Best regards, Dirk

@ Dirk- I found out but that book is not available in India. Im trying to buy it from some other websites. Thanks a lot.It will be of great help if you can get me the information setup. It will be very kind of you. thanks for the help.

Any updates please. im waiting for more info on this !!

Dear Venkatesh, my Old colleagues who have assembled the setup are retired, and the setup has been disassambled in the meantime, and there is nobody left whom we may contact for drawings etc.but I will try to contact them privately, not knowing if this will bring us further...

Dirk,

I have a doubt. Can we measure the thickness of metal thin films or polymer thin films in the range of 30-100 nm using tolansky method???

Is there any other way to measure this range with basic optics???

please help me i'm in need of it very much.

Here is an interference method using optic color pattern for identification of film thickness. As I understand, it's valid for thin films as well.

Dear Venkatesh, yesterday I got a (private) contact with one of my old colleagues - unfortunately it seems as if all the knowledge has gone ...

I have extracted a more precise drawing of the paper I recently sent to you - maybe this helps you for your purposes (see attachment). Hope this helps, you simply need to feed in the light of a spectroscopic light source (Na-lamp, Hg-lamp., etc) into your mike...

In addition to your question two days ago: I already did experiments with films of about 10-20 nm thickness, and the method worked perfect.

Another quite easy thing that you may do for metllic films is simply to measure the transmission: Provided that you don not have holes in your film, then you may easily calculate the thickness - this works quite well if you make use of several different wavelength and calculate the thickness for those wavelength individually.

Hope this helps, Good luck, Dirk

Thanks a lot Dirk and Sergei. Thanks alot