The main objectives are to get 3D surface image of nanoparticles and to quantify its surface roughness accurately. Based on literature, RMS is the best method to calculate the surface roughness of the nanoparticles. is there any limitation associated with the frequency of AFM measurements?
Are there any other options available for the same purpose of surface roughness measurements/quantification in nanoparticles?
Nanoindentation is an alternative technique to measure the RMS value of particles as well as thin films. For more details go through below links. These articles might be helpful.
http://onlinelibrary.wiley.com/doi/10.1002/app.43532/full
http://www.sciencedirect.com/science/article/pii/S0032386116301227
Dear
try to use your 3D image with SPIP software and ask for roughness report
Parameters:
SPIP Classic
Sa [nm] averge
Sq [nm Root mean square (RMS) roughness
Sz [nm] The maximum valley depth
Sv [nm] Ten-points mean height roughness
Sp [nm ]maximum peak height
these parameter help you toget good idea about the type of you sample surface
In order to measure surface roughness on particles that small you will need to use a very very sharp AFM tip say 1-2 nm. I suggest this free software http://www.wsxmsolutions.com/ for the analysis. In terms of the number of measurements, you should measure as many particles as you can for decent statistics. I would say that the minimum would be 10 and use the student-t distribution but better to have more perhaps 20+. Time is typically the limitation.
This problem presents some interesting challenges for AFM.
Measuring roughness on a flat surface using AFM is straightforward, as long as the features making up the roughness are significantly larger than the AFM tip radius. However, if the lateral dimensions of the particles are
The profile of a particle taken will be a convolution of particle and tip shape, as can already be guessed from preceeding comments. Pretty much the same actually applies to STM. The common wisdom is that while you can measure the height of the particle pretty well (if you know what you do), you have little chance to learn much about its shape.
This is only different if
- the particle possesses a sufficiently flat surface. Inthis case there exists nice STM work (Group of Heinz Hövel, maybe 5-10 yrs ago, STM on gold particles grown in HOPG-nanopts, if I remember right.) I am not aware of AFM measurements of similar quality on nanoparticles.
- you have a very stable tip and a superb reference object you can use to characterize the tip to an extent which allows you to understand (at least to some extent) the kernel of your convolution. then you can try a (numerical) deconvolution, which I would nevertheless predict to be a really difficult task.
And to address a possible misunderstanding: RMS roughness is not a statistical analysis of some number of scans (especially not ot the same location in space, since then they should all be the same), but a numerical characterization of a (rough) profile, which ideally woulld be known/measured with perfection.
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