Doublet Separations #

Mo 3d = 3.2 eV

Mo 3p = 17.4 eV

Mo 4p = 2.1 eV

Common Overlaps for Mo 3d #

S 2s – Ce 4p – Nd 4p – Th 5p – Ta 4d – Cs 4s – Se 3s – Fr 5s – Pm 4p – Pr 4p – Rn 4f – Rb 3p

Auger Energies #

Note – these are listed in KINETIC ENERGY

Mo LMM ≈ 185 eV

Common Binding Energies – Mo 3d #

Theory and Background #

Molybdenum, a transition metal, exhibits various oxidation states, commonly Mo(0), Mo(IV), and Mo(VI), which can be distinguished by their unique binding energies in the XPS spectra. The Mo 3d core level is particularly significant, with the 3d5/2 and 3d3/2 peaks providing detailed information about the chemical state and environment of molybdenum atoms. For instance, Mo metal typically shows a binding energy around 228.0 eV for the Mo 3d5/2 peak, while MoO₂ and MoO₃ exhibit binding energies around 229.5 eV and 233.1 eV, respectively. The analysis of these peaks can reveal insights into the oxidation state, chemical composition, and potential surface reactions of molybdenum-containing materials. Additionally, factors such as Coster-Kronig broadening and the presence of overlapping peaks from other elements (e.g., sulfur in MoS₂) must be considered for accurate interpretation. This makes XPS a powerful tool for studying the surface properties and chemical behaviour of molybdenum in various applications, from catalysis to electronic materials.

Experimental Advice #

Molybdenum XPS analysis is typically performed on the 3d region (Figure 1). This region commonly overlaps with the S 2s region, which may complicate the deconvolution of molybdenum sulfates. Additional regions which may overlap with the Mo 3d region include Ta 4d, Cs 4s, Se 3s and Ce 4p (only slightly, but record an extended region to the low binding energy side to aid deconvolution). The peaks have a reasonable doublet separation of 3.15 eV.

Data Analysis Guidance #

The peaks of Mo metal are asymmetric in shape, however the oxides will possess a symmetric shape.

Mo 3d overlaps with S 2s, so if modelling MoS2 materials, this intensity must be accounted for when modelling Mo states.

Mo metal, and conductive materials such as MoTe, which have DOS around the fermi level, will be able to undergo Coster-Kronig transitions, resulting in different FWHM for the Mo 3d 5/2 and 3/2 peaks. This transition is forbidden in the oxides, and other non-conductive samples, and as such the peaks do not need to be fit with different peak widths.(5)

Reference Datasets #

Coming soon

References #