Microscopic aspects of the deposition of nanoparticles from the gas phase

The deposition process in a homogeneous electric field, and the subsequent microscopic arrangement of charged, metallic nanoparticles in the size range below 100 nm on flat substrate surfaces is described. The main aspect of the investigation is the transfer of the particles from a three-dimensional distribution in the gas phase into their arrangement on the substrate surface, in dependence on particle–particle interactions and on Brownian motion. For this purpose, a trajectory model has been developed, which takes into account the flow field above the substrate surface, the electric field, the interactions of incoming particles with the substrate surface and with already deposited particles, as well as Brownian motion. The results from the trajectory calculations are compared with experimental results, obtained by scanning electron microscopy investigations of deposition patterns, created by deposition of indium and gold nanoparticles in an electrostatic precipitator. The particle diameter, the particle charge, the substrate material, the electric field strength and the number of particles deposited per unit area have been varied.