[Zurück]

R. T P, I. Unlu, S. Barth, O. Ingolfsson, H. Fairbrother:
"Electron induced surface reaction of bimetal FEBID precursor molecules HFeCo3(CO)12 and H2FeRu3(CO)13";
Vortrag: CELINA 2017 The fourth meeting of COST Action CM1301, Porto (eingeladen); 13.09.2017 - 16.09.2017.

HFeCo₃(CO)₁₂ [1] and H₂FeRu₃(CO)₁₃ [2] are precursor molecules used in FEBID to fabricate FeCo
and FeRu bimetallic nanostructures, respectively. To date, bimetallic nanostructures have been
fabricated in FEBID by mixing two different metal precursor molecules using dual or multichannel
precursor gas injection system [3]. However, this approach has limitations to get a good control over
the deposit and reproducibility is poor. The use of precursor molecules like HFeCo3(CO)12 and
H₂FeRu₃(CO)₁₃ in FEBID may offer a rout to eliminate these difficulties.

In fact, nanostructures fabricated with HFeCo₃(CO)₁₂ in FEBID have metal content of >80% [1],
with excellent reproducibility. In contrast, nanostructures fabricated using H₂FeRu₃(CO)₁₃ in FEBID
show metal content of only <26% [2]. The different behavior of HFeCo₃(CO)₁₂ and H₂FeRu₃(CO)₁₃ in
FEBID motivated us to study the bond breaking reaction of these precursor molecules adsorbed on a
surface, using UHV surface science approach based on X-ray photoelectron spectroscopy (XPS) and
mass spectrometry (MS).
From the XPS and MS data, we observed that the initial electron induced surface reactions of
HFeCo3(CO)12 and H2FeRu3(CO)13 are similar, creating a partially decarbonylated intermediate of the
form HFeCo₃(CO)_x (x_avg~3) and H₂FeRu₃(CO)_x (x_avg~4,5), respectively. During typical FEBID
experiment, the partially decarbonylated intermediate will experience the effect of either additional
electron exposure or transformations initiated by thermal instability. With further electron irradiation,
XPS data shows that the CO ligands remained in the HFeCo3(CO)3 intermediate decompose into C and
O but the CO ligands in the HFeCo3(CO)3 intermediate are thermally unstable at room temperature
and desorb almost completely. Consequently, deposits created in FEBD from this precursor will
experience the following sequence of elementary reaction steps:
HFeCo₃(CO)₁₂(ads) + e- 􀃆 HFeCo₃(CO)₃(s) + 9CO(g), FeCo₃(CO)₃(s) + Δ 􀃆 FeCo₃(s) + 3CO(g)
In contrast, additional electron exposure or annealing of the H2FeRu3(CO)x (xavg~4,5)
intermediates do not lead to significant CO desorption or CO decomposition. FEBID structures created
from this precursor will therefore experience the following sequence of elementary reaction steps:
H₂FeRu₃(CO)₁₃(ads) + e- 􀃆 H₂FeRu₃(CO)_x(x ~ 4,5)(s) + 8.5 CO(g), H₂FeRu₃(CO)_x(x ~ 4,5)(s) + e-/Δ 􀃆 most CO ligands are retained
References
[1] F. Porrati, et al., Nanotechnology 26, (2015): 475701.
[2] R. K. T P et al., Beilstein Journal of Nanotechnology. (2017): submitted.
[3] M. Winhold, et al., ACS nano 5 (2011): 9675-9681.
Acknowledgments: This work was supported by the Icelandic Centre for Research (RANNIS) and the University of Iceland Research Fund (UIRF). RKTP acknowledges a doctoral grant from URFR and financial support from the COST Action CM1301 (CELINA). DHF thanks the National Science Foundation for support of this work through the linked collaborative grants CHE-1607621 and CHE-160754.

http://publik.tuwien.ac.at/files/publik_263830.pdf