Size and position control of chains or arrays of nanoparticles by surface-plasmon-polariton-induced thermocapillarity

Surface free energy minimization, driven by capillary forces, may lead to morphological changes of wires (e.g. disintegration into a droplet chain which is known as Rayleigh instability) and layers (dewetting). At nano-scale dimensions, capillary effects are much more pronounced than in macroscopic systems due to the large surface-to-volume ratio. On the other hand, capillary-driven self-organization processes are subject to increasing fluctuation with decreasing dimensions, which mostly prevent the formation of regular structures with long-range order. In this contribution, we predict by means of atomistic Monte Carlo simulations a novel method to fabricate size- and position controlled 1D- and 2D-patterns of nanoparticles. Our prediction rests on the temperature dependence of surface tension – the origin of the wellknown thermocapillarity. Uncompensated forces occur due to surface temperature gradients. These forces may have considerable impact in the nanoworld, thus, leading to material transport and structure formation on short time and length scales. A surface tension gradient (also responsible for the Marangoni effect) triggers the biased migration of atoms from hot to cold regions by surface diffusion. A periodic temperature gradient on the surface of a wire or a layer may be achieved by a surface-plasmon-polariton (SPP) wave or even by a SPP wave interference pattern. For SPP excitations with long wavelengths (e.g. by a CO2 laser), sufficiently strong steady-state temperature gradients may be produced. However, pulsed operation might be necessary for shorter wavelengths. We predict by kinetic Monte Carlo simulations that the regularity of nanodroplet chains, that form during a self-organized disintegration of nanowires, might be considerably improved by SPPs. If the SPP wavelength is commensurable with the inherent Rayleigh wavelength of the nanowire disintegration, the SPP-induced temperature undulations control the Rayleigh instability. Thus, a regular and long-range order in nanodroplet size and position may be achieved. Similarly, this principle may be used for the fabrication of regular and long-range 2D nanodroplet patterns, if interference patterns of SPP waves on thin layers are achieved.