I have tried the raman measurements of very thin PVDF films (from 70nm to 250nm) using confocal raman spectroscopy by RENISHAW. I have the following doubts, kindly give me suggestions.
1)For PVDF (Polyvinylidene fluoride) thin films deposited directly on glass or Si, it was found difficult to focus and I do not get proper peaks, whereas when they are grown on metal layers we could easily focus the surface and proper peaks were seen. Why does this occur? Is it because of the focussing problem only or anything else?
2) Is crystallinity a factor to give raman peaks as like XRD? What will be the raman analysis of polymorphous samples?
3) Will metal layers like Ag, Al, Cu, Au, Pt (at 50nm thickness) give any raman peaks?
Raman intensity depends on the bond polarisability. Consequently the PVDF signature is not very strong and using a x50 or x100 microscope objective a thickness almost equal to the vertical spot size (20 to 5 µm) is needed to get a 'good' spectrum. At least 1 µm thick layer is needed to get something.
see
http://dx.doi.org/10.1088/2043-6262/4/1/013001
http://dx.doi.org/10.1166/qm.2014.1135
Gouadec & Colomban
Progress in Crystal Growth & Characterization Materials 53 [1] (2007) 1-56.
all available on RG
The depth of penetration of the Raman spectra has to be taken into consideration. Please view my paper on Raman intensity of DLC and Si-DLC films deposited on nitrile rubber for details on how I carried out my Raman study on nitrile rubber substrates
On metals the optical response is different, for example high reflectance. In your experiments, sample homogeneity may be different for the various substrates.
Thank you Michael Lubwama , Annemarie Pucci, Tamás Váczi for ur suggestions. Belated new year wishes to all
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