Local flux governing mechanism for the self-assembly of silver nanoparticles on ripple patterned templates

On ripple patterned substrates produced by ion beam sputtering, silver nanoparticles are successfully produced by using angular varied PVD electron beam evaporation method. Nanoparticle self-assembly is observed even in a non-shadow deposition region, though ripple pattern has a shallow modulation of ∼2 nm. Therefore, the contribution of the surface adatom diffusion kinetics and the local flux variation seems to be important for this self-assembly process. Due to lower incident flux and lower adatom energy PVD e-beam evaporation deposition method is proven to be superior to sputter deposition for the nanoparticles self-assembly. The self-assembly of nanoparticles is largely dependent on angle of incidence θ, rate of deposition, and deposition direction with respect to the surface topography. We propose the local flux variation model based on the ripple asymmetric tilt and the local incident angle which explains the self-assembly process nicely in terms of the nanoparticle size distribution. The optimum incident angles are calculated to be θ = ± 70° with respect to surface normal by using an analytical rippled surface model for the best alignment of nanoparticles as well as nanowires that are indeed obtained experimentally even though these angles are out of the shadow deposition regime. (papers)