Hexagonally ordered arrays of spherical Au nanoparticles (NP) exhibiting narrow size distributions were fabricated on top of SiO₂ as well as Sapphire substrates applying a micellar preparation technique. This approach allows control over the particle diameter (1nm to 12 nm) as well as the interparticle distance (30 nm to 150 nm).

Such NP arrays of different starting diameters were ion irradiated with 200 and 350 keV Ar⁺, respectively. It turned out that the Au particles were surprisingly stable conserving their almost spherical shape during the bombardment, which, on Si/SiO₂ resulted in completely buried particles corroborating a previous report [1]. Combining HRTEM data with AFM height measurements allows a quantitative analysis of the phenomenon. It will be demonstrated that additionally to necessary thermodynamic driving forces related to an ion induced enhancement of the substrate viscosity², sputtering of the NP with a size-dependent sputter yield has to be included in the description of the experimental results in order to improve agreement [2]. This work has been extended to Au NPs on Sapphire where the burying effect is completely suppressed and, thus, pure sputtering can be studied confirming size-dependent sputtering.

[1] X. Hu et al., J. Appl. Phys. 92, 3995 (2002).

[2] A. Klimmer et al., Phys. Rev. B 79, 155427 (2009).