Hi,
These measurements are new to me so apologies for the naive questions. How can I use profilometry or ellipsometry to measure the thickness of spin coated quantum dot films on CVD graphene (on a copper substrate)? Given the uniform coverage across the film, I do not have any obvious steps that would be well suited for profilometry. I saw a few papers use ellipsometry but I am not sure what would be the right fitting procedure to use to accurately measure the thickness. Any help in either of these directions would be very helpful!
You can create the step and then measure the step height with AFM or profilometry. The step can be done by scratching the film or using lift-off. For spin coated films usually you can scratch the film using a soft sharp object right after deposition so that the film is still soft, but make sure to dry it before measurement, otherwise you will damage the stylus (tip).
If using ellipsometry you will have to build a model for your QD film first, but this is far from trivial. how is the absorption spectrum of your PbS film? and what type of ellipsometer do you have? is it multiwavelength? if yes what is the range? If your film is transparent in some region that is within the range of your ellipsometer, you can measure your film in that region and use a transparent model such as a Cauchy model to fit refractive index and thickness. Contact me if you have more questions about this.
I added pictures using both methods. In the profilometry measurement, I scratched the film using a pipette tip, dry the film and measure valley depth. In the ellipsometry measurement, I measured the film at three angles of incidence in the 600-1000 nm range where my QDs are transparent, and use a Cauchy equation to fit RI and thickness. Both methods are always in very good agreement.
Hi Raul Montes,
Thank you for the detailed explanation. Will be trying this out soon!
Thank you to others for your inputs as well!
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