Composition control and flexibility through novel bimetallic precursors

Bimetallic precursors for FEBID are expected to enable the fabrication of deposits with optimum composition control and reproducibility. The stoichiometry of the complex defines the ratio of the metals to be deposited independent of pressure fluctuations that are a concern in dual source processes. Following this approach, the novel precursor HFeCo₃(CO)₁₂ was synthesized and shown to yield FeCo₃ metallic phases with predefined stochiometry and metal content up to 80%:

• F. Porrati, M. Pohlit, J. Müller, S. Barth, F. Biegger, C. Gspan, H. Plank, M. Huth:
  Direct writing of CoFe alloy nanostructures by focused electron beam induced deposition from a heteronuclear precursor,
  Nanotechnology 26 (2015) 475701.

The high metal content of HFeCo₃(CO)₁₂ correlates with a surprising wealth of fragmentation channels through DEA that extend up to electron energies of 20 eV:

• Ragesh Kumar TP, Ragnar Bjornsson, Sven Barth, Oddur Ingólfsson:
  Formation and decay of negative ion states up to 11 eV above the ionization energy of the nanofabrication precursor HFeCo₃(CO)₁₂,
  Chem. Sci. 8 (2017) 5949-5952.

• Ragesh Kumar T.P., Sven Barth, Ragnar Bjornsson, Oddur Ingólfsson:
  Structure and energetics in dissociative electron attachment to HFeCo₃(CO)₁₂,
  Eur. Phys. J. D 70 (2016) 163.

Interestingly, another new precursor H₂FeRu₃(CO)₁₃ performs less favourably in FEBID yielding deposits with much lower metal content and Fe content below the precursor stoichiometry. This is in line with the fundamental electron-induced fragmentation that reveals a tendency towards metal-metal bond dissociation:

• Ragesh Kumar T P, Paul Weirich, Lukas Hrachowina, Marc Hanefeld, Ragnar Bjornsson, Helgi Rafn Hrodmarsson, Sven Barth, D. Howard Fairbrother, Michael Huth, Oddur Ingólfsson:
  Electron interactions with the heteronuclear carbonyl precursor H₂FeRu₃(CO)₁₃ and comparison with HFeCo₃(CO)₁₂: from fundamental gas phase and surface science studies to focused electron beam induced deposition
  Beilstein J. Nanotechnol. 9 (2018) 555–579.

Further increased flexibility in fabrication has been demonstrated by combining a bimetallic precursor with a second precursor. This approach was exploited to fabricate nanopatterned layers in a direct-write process:

• F. Porrati, R. Sachser, G. C. Gazzadi, S. Frabboni, A. Terfort, M. Huth:
  Alloy multilayers and ternary nanostructures by direct-write approach,
  Nanotechnology 28 (2017) 415302.