ION BEAMS' HYDRODYNAMIC APPROACH TO THE GENERATION OF SURFACE PATTERNS

Amorphous solids can flow given the right timescale. In lead pipes or glaciers, solid flow can be seen in great detail, but it can also be manipulated by adding flaws. Ion Beam Sputtering (IBS) is a method in which ions with energies between 0.1 and 10 keV strike on a solid target, causing the formation of defects and their dynamics as well as degrading its surface and creating ordered nanostructures. Despite being technologically intriguing, a fundamental understanding of the nanopattern creation processes that take place under IBS of amorphizable targets has not been developed, with recent research on Si having mainly questioned knowledge collected over the last two decades. In the past, a number of interfacial equations have been presented to explain these phenomena. Typically, these equations involve nonsystematic addition of various contributions from surface diffusion, ion sputtering, mass redistribution, etc. In order to create a broad framework into which various mechanisms (such as viscous flow, stress, diffusion, or sputtering) can be added, under general physical conservation rules, we here take advantage of the general idea of solids flowing due to ion impacts. This approach enables a systematic evaluation of the relevance and interaction of several physical factors influencing surface pattern generation by IBS as opposed to the formulation of phenomenological interfacial equations.