Hi Fellows, I would like to know if there is a good way to characterize surface defects or strain. Our recent finding shows that scratched surfaces show different electrochemical properties from non-scratched surfaces. However, the scratch did not generate any SEM-level cracks/fractures (invisible in SEM). I am thinking either nano-cracks were generated on the surface or a strain field was built up. My initial thought was using TEM to look at it. However, the sample preparation may cause new strain field if a FIB method was used. Is there any way to detect such small defects (if any) or the strain field?
If surface scratches are within nanometer scale, you may use AFM instead of SEM or TEM.
AFM deals with surface topology, and data output are Roughness Parameters, where you can relate them with the change of electrochemical properties.
dear Xin Xu ;
try to use Atomic force microscopy (AFM), more details in the reference;
Article nanoDAC - A method for fracture mechanical characterization ...
This is a difficult task.
I would try to connect surface distortions with deviations of the lattice parameters of surface from the bulck ones. Then the parameters calculated from the X-ray diffraction lines at small angles will differ from the parameters calculated from the lines at large angles, since at small angles the angle of incidence is closer to the grazing angle. Consequently, the surface layer plays an important role in small angles. Of course, the parameters calculated from the lines at high and low angles will differ anyway. However, if the surface has no distortions, then the dependence of the parameter on the line angle will be described by the Nelson-Rhiley function. Deviations may indicate a deviation of the parameters of the surface layer from the volume.
True, this will only work if you have lines with a large interplanar spacing, so that their angle is very small.
You can also try to play with the depth of penetration. If you can see the effect of a scratch, then the depth of the distorted layer is on the order of microns. You can try using diffraction in soft and hard radiation. But changing the wavelength will lead to a difference in the accuracy of determining the parameters. Therefore, if the effect is small, then it will be difficult to notice.
It's too bad your surface layer is so large. I know a good method for finding distortion in a 10-15 angstrom layer. This is photoelectron diffraction. But for a layer of micron thickness, probably only the method of a standing X-ray wave is suitable. And I don't know much about him.
You can use Atomic Force Microscopy (AFM) rather than Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM)
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