I want to quantify some roughness parameters using AFM data. I tried to quantify some of them by Gwyddion software but its HHCF doesn’t have a fitting function contemplating all parameters I need.
Fit function that I found in my Gwyddion version:
y = 2sigma^2 * ( 1 - exp ( - ( r/E )^2 ))
, where, sigma is the interface width and E is the lateral correlation lenght.
Fit funtion that I was looking for:
y = 2sigma^2 * ( 1 - exp ( - ( r/E )^(2a) ))
, where a is the Hurst exponent.
I also tried to export data to origin and tried to set a new fitting function, but I got stuck on how to build it. Something went wrong since my limit bounds aren't being followed.
If anyone could help me with some insights I will be really grateful.
I guess I just got the right way to do it.
For anyone who have the same interest, I used origin to get there.
I made a new fitting function and it worked well. It took a while to set all stuffs, but with patience I got it.
If anyone is having trouble with that, feel free to text me and maybe I can help.
A very good video description on how to make user defined function and extract the fitting parameter using origin is explained in this youtube video
https://www.youtube.com/watch?v=WLj6bblDFS8
Hope this is what you wanted
best of luck
The log - log plot of the HHCF data usually has a linear region followed by a plateau. Since for small lateral lengths, the value of HHCF grows as r^(2*alpha), by performing a linear fit of the log - log plot you can calculate the Hurst exponent. Interface width can be calculated from the plateau region. For the plateau region, HHCF grows as 2*sigma ^ (2*alpha). Use this to find sigma.
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