How forces exerted by external fields on adatoms lead to the collective motion of 2D nanostructures

S. Curiotto1, A. El Barraj1, F. Cheynis1, N. Dahech1, N. Combe2, O.P. Louis3, F. Leroy1, P. Müller1

1Aix Marseille University, CNRS, CINaM, Marseille, France

2Centre d’Elaboration de Matériaux et d’Etudes Structurales, Toulouse, France

3Institut Lumière Matière, UMR 5306, Université Lyon 1, France

Adatom diffusion plays a key role in surface physics. External fields due to a gradient of electrical potential or to a gradient of temperature are well known to create biased adatom migration and lead to the phenomena of electromigration or thermomigration. However, such gradients can also drive the motion of micron-sized nanostructures [1] . The global movement of such 2D nanostructures (positive or negative islands) results from the individual motion of adatoms but moreover needs the presence of an anisotropy of the adatom diffusion between the exterior and the interior of the 2D nanostructure [2]. In this talk we will focus on the description of electromigration and thermomigration forces respectively expressed in terms of effective charge Z* and effective heat of transport Q* [3,4]. A clear theoretical understanding of these physical quantities combined to careful in-operando experiments obtained by Low Energy Electron Microscopy (LEEM) (1) leads to a better comprehension of the mechanisms hidden behind the phenomenological quantities Z* and Q* and (2) enables to extract these elemental atomic quantities from the global nanostructure motion [6].

References
[1] S. Curiotto et al. ACS Applied NanoMaterials, 3 (2020), 1118
[2] S. Curiotto et al. Appl. Surf. Sci. 469 (2019) 463
[3] F Leroy et al. Phys. Rev. B 102 (2020) 235412
[4] F. Leroy et al. Phys. Rev. Lett. 131 (2023) 116202
[5] O. Pierre-Louis et al., Phys. Rev. B 62 (2000) 13697
[5] A. Roux et al. Phys. Rev. B 108 (2023) 115410
[6] S. Curiotto et al. Appl. Phys. Lett (submitted to)