Laser ablation and secondary ion mass spectrometry of inorganic transition‐metal compounds. Part I: comparison between static ToF‐SIMS and LA‐FTICRMS

Abstract

Most of the first-row transition-metal oxides, M(A)O(B) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) were examined by static secondary ion mass spectrometry (s-SIMS) and laser ablation/ionization Fourier transform ion cyclotron resonance mass spectrometry (LA-FTICRMS). Positive and negative ions show strong correlation between the studied oxide and the detected cluster ions. Specific M(x)O(y) (+/-) species were systematically observed with both MS techniques for each investigated M(A)O(B) transition-metal oxide. Moreover, the ion composition and ion distribution are greatly dependent on the ionization technique. Laser ablation (LA)/ionization leads to larger cluster ions (ionic species with nearly hundred atoms were in particular detected for Sc2O3 and Y2O3 oxides), whereas hydrogenated, dihydrogenated, and sometimes trihydrogenated species were observed in s-SIMS. However, the ion distribution for a given M(x)O(y) (+/-) ion series (i.e. ions including the same number of metal atoms M) generally presented important similarities in both techniques.Finally, it was demonstrated that the chemical state of metal atoms in the observed ionic species is closely dependent on the metal electronic valence shell. High valence states (+III, +IV, +V, and +VI) are favored for metals with a less-than-half full valence shell configuration, whereas for other first-row transition metals (manganese, iron, cobalt, nickel, copper and zinc) lower metal valence states (0, +I or, +II) are involved.

Laser ablation mass spectrometry of inorganic transition metal compounds. Additional knowledge for the understanding of ion formation

“…The spectra of the different vanadium oxides contain differences in oxyanion relative abundances that may be used for identification of the solid materials based on their mass spectra. As previously reported [22], the different vanadium oxides emit the same species by laser ablation. The convention adopted for writing the compositions of the vanadium oxyanions is to denote them as combinations of small anions and small neutral molecules, i.e., denoting V 3 O 7 Ϫ as (VO 2 ) 3 O Ϫ .…”

“…FTICR-LMMS has been described in details elsewhere [22] as well as the instrumental parameters that were used.…”

“…The convention adopted for writing the compositions of the vanadium oxyanions is to denote them as combinations of small anions and small neutral molecules, i.e., denoting V 3 O 7 Ϫ as (VO 2 ) 3 O Ϫ . This notation does not connote explicit structural chemistry, in this case two discrete oxide molecules ionically bound by an oxide anion, as it is well known that charge delocalized ( [22] and references therein), and that atoms are partly covalently bound by transition-metal-oxygen bounds. We adopted this approach for writing the ion formulae to maintain consistency with prior publications and because it facilitates discussion of ion formation mechanisms.…”

“…Yttrium oxide was used in this evaluation because (1) this oxide produces a significant yield of cluster ions and, (2) only one building block, i.e., Y 2 O 3 Ϫ is involved in the structure of the observed cluster ions, in contrast to other compounds investigated [22]. This model produced high kt values for spectra obtained in LA-MS experiments at 355 nm for all the examined cluster ion series, which indicates inefficient or slow dissociation during and/or after laser matter interaction and/or significant recombination and/or aggregation processes.…”

“…The comparison of LA-MS and s-SIMS measurements in the study of transition-metal oxides [22] allowed us to highlight some periodic trends and to demonstrate the relation between the distribution of metal valence sites in M x O y ϩ/Ϫ cluster ion and the electronic configuration of the metal. Our purpose in this paper is to propose general principles governing cluster ion formation by laser ablation.…”