Hello Sir,
Thanks for replying
(1) The transmittance % is more than 100% i have not changed the values this is just the data that i have taken from the instrument
(2) There may the instrumental error at 860 nm
so is this data will not solve my problem?
Hi Neharana, you can get started with this :Determination of Refractive Index and Film Thickness from Interference Fringes by N. J. Harrick, @ dx.doi.org/10.1364/AO.10.002344
Kai is absolutely right, you need to figure out what went wrong in collection of the spectra to give you >100 % transmittance -- my guess, wrong baseline correction.
You probably need to expand the wavelength range to get few more fringes to make a sensible estimation. Most of the newer absorption spectrometers comes with this tool in-built in their software, so check it out.
Hope this helps,
Palash
Good afternoon,
From your data you cannot know both the thickness and the index of refraction even after correcting for the bugs in these data. You can only measure the optical thickness that depends on the wavelength. Only ellipsometry allows for the dual determination for a transparent thin film on a transparent substrate of known index of refraction. The easiest way is to measure the physical thickness first and then to measure the optical thickness that would give you the index of refraction through a simple division.
Hi Neharana, the data that you have taken from the instrument should have transmittance < 100% to begin with if properly taken, you should not have to adjust / modify. That does not sound right. That goes even for the small kink at ~860 nm, try adjusting collection aperture, step size and scan speed -- and what is must: a proper baseline correction. Palash
These could also be of use for you:
http://optics.unige.ch/alexey/reffit.html
http://www.ime.usp.br/~egbirgin/puma/
Hello Neharana,
You have already received a number of useful suggestions.
It appears to me that the reference you used while taking the data of your (presumably indium tin oxide) sample had smaller transmittance than your sample (eg the standard might have been thicker). This resulted in T > 100%. My suggestion will be to use as reference an identical piece of the substrate material (probably plain glass) that you used to deposit your ITO layer on.
Secondly, it is more customary to find the thickness of a transparent film from the reflection spectrum (remember rainbow colours seen in an oil film on water). But as Charles Hirliamann has pointed out, you need to know refractive indices of your substrate and film unless you are using ellipsometry. In some spectrophotometers, you can obtain the normal incidence reflectance spectrum, which will allow you to calculate the film thickness.
Thank you all for these suggestions
Actually i have deposited my ZnO film on ITO coated glass substrate and when i have performed my uv study for reference i have taken bare ITo coated glass i dont know where is the problem
anyway i will repeat the measurements again
i specially thank to Dr. Palash Gangopadhyay and Kanad Mallik
With Regards
Neha
Hello Neharana;
From correct transmittance data, it is possible to determine both the thickness and the index of refraction if you can choice the accurate dispersive law of your thin film (eg: Sellmeier, cauchy, lorentz, ...). That is possible by using an optimisation algorithm. See the article:Optics Letters 02/2012; 37(4):449-51. titled: Determination of layer thickness and optical constants of thin films by using a modified pattern search method.
For measuring of thickness and n of ZnO thin film it will be better to use ellipsometeric study ,because some times U.V spectroscopy cannot be used for determination of thin thickness .....good luck
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