Dear colleague Muhammad Taimoor

Have a nice time and good day.

To control the thickness and the homogeneity/ smoothness of thin films there are many factors should be considered.

The preparation by thermal evaporation method may achieve for you the three parameters you want; definite thickness, homogeneity and smoothness as follow:

The preparation of thin films using thermal evaporation technique by coating unit type Edwards E-306 A supported by

1-   Quartz crystal monitor type Edwards FTM5  and  

 shutter to control the value of thickness.

2-   Rotating sample holder to control the homogeneity and the smoothing of the produced film.

I think this resolve your facing problems.

I wish that be useful and help you.

Yours

A. El-Denglawey

Dear colleague Muhammad Taimoor,

To form a uniform film of quantum dots can be used a method of a speen-coating. In my articles you can read about this in more detail.

Best regards,

Sergey.

Spin coating is one method to disperse the QDs. The process needed to get reproducible films remains somewhat of an art rather than a science. It also produces mostly a micro-patchy coverage of QDs in 2D. An alternative method is to make Langmuir films of the QDs and then cast them on to the solid. This can produce single layers. Some of our preliminary work in this direction is given at this link.

https://www.researchgate.net/publication/300157108_Digital_Imaging_and_Fluorescence_Characterization_of_Langmuir_Film_of_Quantum_Dots

You mention that you want a film that is ~2 micron. For a QD at 10nm diameter, this is a film that has about 20 layers of QDs. I doubt, for this need, that you will find any method that can produce a dense, uniform film in 2D that is also dense and uniform in 3D. You will need to include a co-additive to disperse the QDs from clusters.

Conference Paper Digital Imaging and Fluorescence Characterization of Langmui...

Dear Muhammad Taimoor,

You can refer to my work in the following link. I was able to get thin films of ~ 1 micron using spin coating method. But my requirement was to embed CQD in glass matrix using sol-gel method, and finally produce thin films of this mixture on glass substrate.

I hope my article can be of help to you.

https://www.researchgate.net/publication/277019133_Acid-free_sol-gel_fabrication_of_glass_thin_films_embedded_with_II-VI_colloidal_quantum_dots

Regards,

Hemang

Article Acid-free sol-gel fabrication of glass thin films embedded w...

Dear A. Eldenglawey,  Jeffrey J Weimer S. Dayneko and Hemang Jani,

Thank you for your suggestions.

Thermal evaporation in our case is not possible because I was told that any temperature above 50 C would damage the CQDs.

Actually, I have a hollow cylinder of SiO2 with a diameter of  5 microns (as shown in the file attached). I would like to fill this hollow core with CQDs. This hollow core is ~2 micron deep.  

I have tried the spin coating and sonication, but I was unable to control the uniformity of the filling. Do you think if it would be possible to fill up the core with, for example, Langmuir-Schaefer method?

Thanks regards,

Taimoor

This is an interesting application. I am optimistic, but I would need to know more about the sample configuration. We'd need to discuss this privately.

Dear Prof. Weimer, I have sent you a private message. Kindly check your inbox.