Surface migration of Si reactive nanoparticles
F. Leroy1, Y. Saito2, F. Cheynis1, E. Bussmann 1,*, O. Pierre-Louis3, P. Müller1
1
CINaM, UMR 7325 Aix-Marseille Université/CNRS, Marseille France
Department of Physics, Keio University, Yokohama, Japan
3
ILM, UMR 5306 Université Lyon 1-CNRS, Villeurbanne, France
E-mail: leroy@cinam.univ-mrs.fr
2
Nanoparticles diffusion on surfaces has recently received new attention because of its
theoretical interest and potential technological applications. Indeed surface diffusion
processes of 3D Nanoparticles on a reactive interface may be a new approach for selfassembling nanoparticles. Recent articles have provided a few examples of spontaneous
motion of liquid droplets [1,2] or solid clusters [3,4] on solid surfaces. More specifically, the
chemical reactions [5] that occur at the interface between the particle and the underlying
substrate can drive nanoparticles towards a variety of non-equilibrium behaviours such as
self-propelled motion [3,4] on a surface or the formation of trenches on solid substrates [5,6].
Here we use in situ Low Energy Electron Microscopy (LEEM) and Atomic Force
Microscopy (AFM) to study the spontaneous motion of 3D silicon nanoparticles onto SiO2
substrate [7]. We report on the
observation of the random walk of
solid-state silicon islands during
annealing at high temperatures. The
Mean Square Displacement (MSD) of
the islands exhibits three regimes. At
short times, the islands undergo
equilibrium diffusion and begin to etch
the surface. Then, an unusual size
independent diffusion-like behavior is
observed with a linear increase of the
MSD. This behavior is attributed to a
pinning instability of the triple-line.
Finally, as etching proceeds pits are
formed in the substrate and the islands
are self-trapped in their own pits. Fig. LEEM images (E = 4.5 eV) of Si/SiO2 islands
during annealing (t1,2,3 = 0, 15, 30 min; T= 1230 K).
Kinetic Monte Carlo simulations
(b) Example of trajectory of the center of mass of one
provide a consistent picture of the Si nanoparticle. (c) Time evolutions of the Mean
mechanisms at play in the experiments.
Square Displacement and mean projected area of Si
islands under reaction (T =1280 K).
Acknowledgements
We thank ANR 13 BS-000-402 grant LOTUS and JSPS KAKENHU 23540456
* now at Sandia National Lab (Albuquerque, U.S)
References
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[5] U. Denker et al., Phys. Rev. Lett. 94, 216103 (2005).
[6] K. Sudoh and M. Naito, J. Appl. Phys. 108, 083520 (2010).
[7] F. Leroy, Y. Saito, F. Cheynis, E. Bussmann, O. Pierre-Louis, and P. Muller, submitted to PRB