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Title: Effects of laser energy and wavelength on the analysis of LiFePO₄ using laser assisted atom probe tomography

The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative analysis of LiFePO₄ by atom probe tomography are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted field evaporation has revealed distinctly different behaviors. With the use of a UV laser, the major issue was identified as the preferential loss of oxygen (up to 10 at%) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ/pulse from 50 pJ/pulse increased the observed oxygen concentration to nearer its correct stoichiometry, which was also well correlated with systematically higher concentrations of ¹⁶O₂⁺ ions. Green laser assisted field evaporation led to the selective loss of Li (33% deficiency) and a relatively minor O deficiency. The loss of Li is likely a result of selective dc evaporation of Li between or after laser pulses. Comparison of the UV and green laser data suggests that the green wavelength energy was absorbed less efficiently than the UV wavelength because of differences in absorption at 355 and 532 nm for LiFePO₄. Plotting of multihit events on Saxey plots also revealedmore » a strong neutral O₂ loss from molecular dissociation, but quantification of this loss was insufficient to account for the observed oxygen deficiency.« less
 [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1]
  1. Univ. of California, San Diego, CA (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. Univ. of Alabama, Tuscaloosa, AL (United States)
  4. Stony Brook Univ., NY (United States)
  5. Stony Brook Univ., NY (United States); Brookhaven National Lab., Upton, NY (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0304-3991; R&D Project: CO009; KC0302010
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Additional Journal Information:
Journal Volume: 148; Journal Issue: C; Journal ID: ISSN 0304-3991
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY atom probe tomography; LiFePO4; oxides; stoichiometry; molecular dissocation