XPS measurement of fivefold and sixfold coordinated sulfur in pyrrhotites and evidence for millerite and pyrrhotite surface species
XPS measurement of fivefold and sixfold coordinated sulfur in pyrrhotites and evidence for millerite and pyrrhotite surface species
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DOI：
10.2138/am-2001-2-315
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发表时间：
2001-03
影响因子：
3.1
通讯作者：
H. Nesbitt;A. Schaufuß;M. Scaini;G. Bancroft;R. Szargan
中科院分区：
文献类型：
--
作者：
H. Nesbitt;A. Schaufuß;M. Scaini;G. Bancroft;R. Szargan
Abstract Collection of S 2p XPS spectra of millerite (NiS), using a conventional (AlKα) and a synchrotron photon source, demonstrates the presence of one surface species on millerite (NiS) and spectral deconvolution indicates a second surface contribution. The observed surface core-level shift (binding energy = 161.1 eV) is attributed to a surface monomeric species (S2-) whereas the second contribution probably is a surface dimeric species (S22-, binding energy = 162.3 eV). Surface dimers, if present, indicate surface reconstruction of millerite surfaces upon cleavage. Monoclinic (Fe7S8) and hexagonal (Fe10S11) pyrrhotite are non-stoichiometric due to vacancies on metal sites. The conventional S 2p XPS spectra of these phases, which sample primarily bulk sulfur states, reveal contributions from fivefold and sixfold coordinated S atoms, the proportion of which is consistent with structural refinement studies. The more intense signal is derived from S in fivefold coordination (80-85%) and the remainder represents the sixfold contribution. Comparison of a highly surface sensitive S 2p XPS spectrum of pyrrhotite (photon energy tuned to 210 eV) with a conventional S 2p XPS signal (AlKα source) indicates the presence of a monomeric surface species (S2-). Spectral deconvolution of the surface sensitive spectrum indicates another contribution near 162 eV, the origin of which is uncertain. It may represent S atoms in sixfold coordination, surface dimers (S22-) or both.
