We prepare TiO2 samples using Titanium Isopropoxide, Ethanol, and Glacial Acid; We increase the amount of ethanol to decrease the thickness of the layer. However, the layers with thicknesses >40 nm show a rather poor resolution with both SEM and AFM techniques. It is reproducible and depends only on the sample. In the same measurement session, we got good resolution for thin films and bad resolution for thick ones.
We thought it was concerned with some reaction products in the film making it soft(?) and so we annealed samples at 500 C, but the resolution was not improved after that.
What can it be?
What do actually mean with poor resolution? Resolution in my opinion is a property which is related to the instrument. Do you see any indication in the resonance frequency of the cantilever as well as in the phase fwd signal that something is wrong?
please refer to the link below for more details
DOI: 10.1038/ncomms8265 | www.nature.com/naturecommunications
please refer to the link below for more details
https://www.sciencedirect.com/topics/engineering/atomic-force-microscope
Stephan Bigl , I see a phenomenon similar to one discussed in:
Article Imaging soft samples with the atomic force microscope: Gelat...
"
Imaging soft samples with the atomic force microscope: gelatin in water and propanol"
with one exception that my samples are TiO2 and thus not soft. Or soft for some reason.
In other words, the cantilever deflection is not that big and sensitive to the surface.
D. S. Bhagat , the paper is irrelevant.
Dear Mikhail Pylnev ,
In SEM the bad resolution comes from charging effects, since TiO2 is a bad conductor and moreover your samples probably have something “soft” on top (leftovers of the synthesis process). You should try to image using low-voltage.
In AFM I would say that you are having problems due to such “soft” leftovers: if only solid and rigid species where there you shouldn’t have any problem at all. My advice is to use non-contact mode and play with the parameters, mainly with the amplitude of the tip oscillation and the distance between tip and sample.
Hapala, Prokop, Georgy Kichin, Christian Wagner, F. Stefan Tautz, Ruslan Temirov, and Pavel Jelínek. "Mechanism of high-resolution STM/AFM imaging with functionalized tips." Physical Review B 90, no. 8 (2014): 085421.
Arima, Eiji, Huan Fei Wen, Yoshitaka Naitoh, Yan Jun Li, and Yasuhiro Sugawara. "KPFM/AFM imaging on TiO2 (110) surface in O2 gas." Nanotechnology 29, no. 10 (2018): 105504.
Mikhail Pylnev
The change in the worst image when going from thin to thick films can be associated with the rearrangement of the anatase - rutile crystal structure. Check with an X-ray diffractometer.
You can benefit from this research as TiO2 was used and measurements of xrd and Afm were taken, as well as mixed with wo3 to prepare composites.
Thanks to all who answered!
Jose-Miguel Garcia-Martin, I also think so however should not it be gone after a high-temperature annealing? I tried to anneal the sample with leftovers at 500 C for 2 hs and the resolution was not improved.
Azeez Barzinjy , I am not trying to improve the technique. The resolution when scanning samples prepared using other precursors is great!
Yuri Mirgorod , The film is amorphous and there are no peaks in XRD until the high-temperature annealing at 500C. I tried to anneal the sample at 500 C for 2 hs and the resolution was not improved, but anatase peaks appeared in XRD pattern.
Thaqeef Murtada Jawad , your comment is absurd.
Can it be concerned with an increased smoothness of the film? I use a rough FTO(~23 nm) as a substrate and for thick samples, the roughness is halved(~ 9 nm). It may make sense since the particles in the solution are nm-sized. So thin films will inherit the morphology of the substrate and thick would provide an improved morphology and thus it would be harder to measure.
Are there any experiments I can try to prove it?
Hasan Sarigül , no. The XPS spectra of this TiO2 is similar to one prepared by another method using titanium disopropoxide in IPA, but the resolution is bad in the same measurement session for isopropoxide film, while good for disopr.
Dear Mikhail Pylnev ,
No, I don't think that leftovers dissapear with 500C annealing: they can be altered or even become hardened. You should try other methods to remove them, for instance oxygen plasma stripper.
Thank you, Jose-Miguel Garcia-Martin . It contradicts my experience, but there must be a reason for the phenomenon.
We are going to try XPS to check if there are any suspicious species.
Meanwhile, which species can you suspect?
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