I have spin coated nanoparticles over silicon oxide substrate at different speeds and their AFM images show Rq values of 1.33 nm, 1.89 nm and 3.2 nm for these three samples. Also their uniformity between spin coated features decreases in same order as appears from images.
Hi Yadav ,
Well, It can be explained as: The value of surface roughness of thin film is highly dependent on its thickness. In fact, the variation of angular speed of spin coater can significantly alter the film thickness. Usually, the film thickness and its roughness exhibit a progressive decrease at lower angular speed, while the uniformity of that film ultimately improves in most of cases.
I hope you got my point.
Dear Kashif, it may be true for some cases but in general for nanoparticles solution coating case may be different where we are trying to see distribution of nanoparticles instead of coated thin film.
The size of nano particles at different angular speeds of spin coating vary such that the highest is out the substrate and however the AFM images show Rq values of increased values . These affects on uniformity of the films , and so on the values of surface roughness of the film.Also the thickness decrease when angular speed spin coating increase . These factors(grain size of the nano particles , angular speed ,thickness of the films , uniformity, surface roughness, concentration of the solution ,and the distribution of nano particles on the substrate) are depending on each others .
"Ra" is (Average Roughness) while the Image Rmax specifies the maximum vertical distance between the highest and lowest data points in the image. The Image RMS (Rq) is the root mean square average of height deviations taken from the mean data plane, so if Rq is low it means the roughness is low.
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