Elemental Characterization of Al Nanoparticles Buried under a Cu Thin Film: TOF-SIMS vs STEM/EDX

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Abstract
In this work we present a comprehensive comparison of Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and Scanning Transmission Electron Microscope combined with Energy-Dispersive X-ray Spectroscopy (STEM/EDX), which are currently the most powerful elemental characterization techniques in the nano- and micro-scale. The potential and limitations of these methods are verified using a novel dedicated model sample consisting of Al nanoparticles buried under a 50 nm thick Cu thin film. The sample design based on the low concentration of nanoparticles allowed us to demonstrate the capability of TOF-SIMS to spatially resolve individual tens of nanometre large nanoparticles under Ultra-High Vacuum (UHV) as well as High Vacuum (HV) conditions. This is a remarkable achievement especially taking into account the very small quantities of the investigated Al content. Moreover, the imposed restriction on the Al nanoparticles location, i.e. only on the sample substrate, enabled us to prove that the measured Al signal represents the real distribution of Al nanoparticles and does not originate from the artefacts induced by the surface topology. The provided comparison of TOF-SIMS and STEM/EDX characteristics delivers guidelines for choosing the most optimal method for efficient characterization of nano-objects.
Funding Information
  • H2020 Marie Sklodowska-Curie Actions (754364)
  • Horizon 2020 Framework Programme (654360)

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