Generally, if surface roughness increases, coercivity increases as well. Due to the increasing surface roughness, domain-wall pinning started to contribute to the coercivity.
So I etched the polymer substrate and deposited CFB (100 nm, 50 nm, 10 nm).
And I also got this data for 100 nm and 50 nm samples. However, the opposite tendency was observed for the 10 nm sample. Almost there is no coercivity change as surface roughness increases. I don't know why this happened.
All samples are amorphous thin film and don't have anisotropy. And the surface shape is the same as the attached file.
depends on how you measuring it .. generally, it would decrease with increasing surface roughness
What are the depth, size and shape of the etching pits in the substrate compared to the thickness of the CFB film? Do you happen to have island film at such small thickness (as individual Islands in the etching pits)?
Have you observed the domain structure in the film? It may have realized a single-domain state of individual Islands and even superparamagnetism. But if CFB is understood as CoFeB, then with a sufficiently high coercivity in the material, island superparamagnetism is unlikely to be possible.
The shape of etching pits is network structure. As etching proceeds, the size of the structure increases from 50 to 200 nm depth as well. When I took SEM images (100, 50, 10 nm), for 100, 50 nm samples, the distance between pillars is closer. However, for the 10nm sample, the pillars are thin and the distances of the pillars are far. I have uploaded SEM images.
Dear Yungeun Ha,
I saw your other question about magnetic anisotropy in similar samples (Is there in-plane anisotropy of Amorphous CoFeB thin film?). Therefore, taking into account additional information about the morphology of films that you have given in this post (SEM images), and data from the mentioned other post, I will soon give my vision of the problem in a generalized form in my answer to the question about anisotropy (see: https://www.researchgate.net/post/Is_there_In-plane_anisotropy_of_Amorphous_CoFeB_thin_film). Perhaps colleagues will be able to analyze the situation in more detail, adding or refuting my assumptions.
Yes, all samples are same for those two questions. Once I'll try to take cross-sectional image of SEM. But I'm not sure I can get it since substrates are polymer and 10 nm thickness is so thin.
Well, at least you might be able to see what happens in samples with films of higher thickness.
But it may be worth trying to do this also for films with a thickness of 20 nm.
Good luck to you.
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