How to eliminate the substrate effect, we measure the transmittance?

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A. El-Denglawey

Dear Khaoula Ghezali

Have a nice time and good day

السلام عليكم ورحمة الله وبركاته

There is some thing wrong, firstly, this is not the transmittance because the maximum value of transmittance is 1 or 100%. Secondly this is sure the absorbance and Y axes units should be divided by 100 so the values of y-axes will be 1,2,.....,4.

To check your values consider this equation:

Transmittance + reflectance + absorbance = 1

You can send me the measured parameters in an Excel or origin file and i'll process to you.

I wish that is useful and help you.

Yours

A. EL-Denglawey

Khaoula Ghezali

Dear A. Eldenglawey;

but when i eliminate the substrate base line a typical transmittance was obtained !!

how do u explain that ?

Best regards

GHEZALI.K

Abdelhalim Zekry

Welcome!

I agree with the colleague Eldenglawey that what we see looks like the absorbance and not the transmittance.The fall of the transmittance expresses to some extent an increase in absorbance. That is the fall of transmittence means increase in the absorbance. So, your y axis must be clearly labeled as the percentage decrease in the transmittance. It is so that any material in the optical path affects the the overall transmittance. So,yes you have to make your measurements with reference to the substrate material. Fore more information please refer to the paper in the link:http://dergipark.ulakbim.gov.tr/tbtkphysics/article/viewFile/5000025903/5000026140

wish you success

Dear Abdelhalil Zekry;

Thank you soo much

K.GHEZALI

Dear colleague Khaoula Ghezali

Please check the next

1- The transmittance and the absorbance were measuring using one attachment, so check aging your choice.

2- check the substrate position (it may be air).

3- The reference against the sample is clean ITO glass or other.

4- Try reference material (10-30 nm) thickness of the same material on ITO galss could be used as reference material .

Good Luck , Waiting the result.

Ahmed Saeed Hassanien

The following steps must be followed to measure transmittance for any sample by using spectrophotometer:

- Firstly you must measure the transmittance of the used substrate only (You have double slits in each slit put one substrate which used in deposition of thin films) to get the base line and don't eliminate its effect.

- Secondly replace the substrate by the thin-film sample (You have double slits in one slit put the substrate that used in deposition of thin films and in the other slit put the sample itself).

- Thus the spectrophotometer will subtract the transmission of the substrate from that of the deposited sample . Thereby, the obtained measurements will be the transmission of the film only and it will be less than 100%.

Good Luck

Dear Ahmed;

I followed the steps that you have said and I found the curve represented in Figure.

but when I didn't use the substrate firstly, a typical curve was obtained ..

It is impossible to get a transmission 400% ... How???? The incident intensity is 100%. So, the transmission must be less 100%. You may be replaced the slit of the substrate by that of the film sample, the sample didn't fixed well or both of the sample and the substrate didn't fixed. You must make sure everything is fixed well and the holder is placed in its right position.

What is your spectrophotometer type and what is its model???

There are some types, in which you must change the position of some key position when you read the transmission? or There is a special attachment for the transmission or the reflection (Old models of Carl Zeiss).

All my best wishes

Dear Ahmed Saeed Hassanien;

i repeat the measurement several times, in two spectrophotomètre with the control of all the paramètre.

the person responsible of the machine advisable me to make the measure without the base line

Nabeel A. Bakr

Hi, I think that the problem is in the noise at short wavelengths due to glass substrate. Try to sketch your graph starting from 400 nm and beyond.

Of course Noooooo

You must before your measurements make a calibration of your spectrophotometer and measure the base line. With my respect to all, any other things rather than these are considered wrong.

All my best wishes and good luck

Dear Ahmed Saeed Hassanien

that is the thought that I had said to the member

Thanks for the answer

You are welcome dear colleague.

a la votre service,