In my XPS spectral, i detected oxygen group bonded to carbon and in my zinc spectral (note : my sample is ZnO) ...there are two valent zinc species available, (which is unsual as my previous sample always indicated the ones ascociated with Zn-O (Zn2+) only.....so i suspect my sample surface maybe in exist differently than the bulk part. therefore, may I assume based on the XPS analysis that, there some kind of surface states exist? help? SOS...
Yes, surface states and species can be detected by photoelectron spectroscopy. XPS and UPS are generally more surface than bulk sensitive since the electron escape path is just a few nm. So it's completely plausible that you will see a difference between the first, second and following layers.
Just be careful about naming stuff: an atom in surface proximity with a mildly different chemical shift, which sounds like your scenario, is not a "surface state". A surface state is a separate state very close to the Fermi edge, which is delocalized for metals (sometimes called Shockley state) or localized for an insulator or semiconductor (Tamm states/dangling bonds/surface lone pairs).
Without seeing spectra, I'd assume this is a charging effect rather than two states.
Zn doesn't have a big chemical shift, so do you see sinilar shape peaks at similar energy separations on other regions?
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