Sj. Kerber et al., THE NATURE OF HYDROGEN IN X-RAY PHOTOELECTRON-SPECTROSCOPY - GENERAL PATTERNS FROM HYDROXIDES TO HYDROGEN-BONDING, Journal of vacuum science & technology. A. Vacuum, surfaces, and films, 14(3), 1996, pp. 1314-1320
Citations number
31
Categorie Soggetti
Physics, Applied","Materials Science, Coatings & Films
Important progressive alterations in chemical bonding are often realiz
ed through correlations with shifts in thp x-ray photoelectron spectro
scopy (XPC) binding energies nf key elements Fnr example there are use
ful general XPS shifting schemes for such systems as oxides, nitrides,
halides, and even various functional groups in organics. Very general
patterns, based upon location in the periodic table, exist for many o
f these materials even when the structure is not strongly considered.
Unfortunately, apparently because of the lack of direct XPS detection
of hydrogen, there seems to be no general statements in the literature
for describing hydrogen-containing compounds, despite the fact that s
ynergistic shifts obviously exist in the XP-S spectra of elements atta
ched to hydrogen (e.g., for M-O-H vs M-O-M units, where M is a typical
metal). While not attempting a complete review paper, in the present
work we use XPS shifting patterns to evolve a series of interrelated c
ovalency/ionicity arguments to help explain the progressive, periodic
changes in XPS peak locations for such common cases as M-O-H- and M-N-
H-containing systems. These arguments are followed by consideration of
the less dramatic XPS shifting patterns exhibited by metal and metall
oid hydrides, including organic bonding. The formalism concludes with
a discussion of hydrogen bonding detected by XPS. After a select revie
w of the infrequent use made by others to attribute XPS peak shifts to
hydrogen bonding, we consider in some detail two cases recently publi
shed by members of our group. One case involves the formation of -N-H-
N- bonds in proton sponge organic systems, while the other uses XPS to
examine the formation of surface oriented -O-H---O- bonds in the adso
rption of peptides on oxidized metals. In the present article, the XPS
patterns for these two seemingly divergent cases are explained by clo
sely related arguments that may have far reaching generalities. (C) 19
96 American Vacuum Society.