Hello
I wonder how strong the changes in the optical properties (delta, beta) of a film will change with thickness at two X-ray photon energies (~1 keV and ~10 keV). If I have lets say films with 1µm, 100nm, 10nm, 1nm and 0.1nm thickness of the same material, how will delta and beta change over thickness? Should I expect changes within the same order of magnitude or will the change be more drastically by factors of 100 or more?
I would guess, that somebody would have already published something like that but I can't find anything. I would be really grateful for help on that.
Philipp, as you will certainly know, the optical properties (delta and beta) values of any material are defined for a continuous medium with no inner structure, which is however not the case in practice. Thus, if you change the thickness of a "model layer", then the optical properties should not change. However, if you consider a real sample and change the thickness, the micro- and nanostructure of the material will certainly change. Usually, e.g. the grain size will change systematically with film thickness, and also the density will usually increase. However those changes are usually not considered in optical data.
What you may do is extract those properties from e.g. reflection mode EXAFS data of thin films and calculate back the structural properties. Doing so leads to acceptable quality of the fit using simply the density of the bulk material in many cases. However, if the thickness of the layer material changes substantially, then this fit parameter has to be varied accordingly. We have published some results on those comparisons/model calculations e.g. in the following manuscripts, however without explicitly showing the extracted data, but just considering the structural properties mostly:
Physica B 283 (2000) 108, J. Synchrotron Rad. 8 (2001) 478, J. Synchrotron Rad. 16 (2009) 443, Thin Solid Films 517 (2009) 3389
And it also works assuming the structure and calculate the reflectivity, as shown in
Surface Science 600 (2006) 4380
Don't hesitate to contact me for furtther details, best regards, Dirk
you can have a look this link .
http://www.quora.com/Whats-the-relation-between-bandgap-the-extinction-coefficient-and-the-index-of-refraction
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