Molecular dynamics simulation of elastic and sputtering properties of nanowires

Nanotechnology became an emerging field during the last few decades. The possibility to create elements having sizes in the nanometer range provides new opportunities for medical applications, various sensors and detectors, and composite materials technologies. However, at the nanoscale the basic physical properties may change unexpectedly including chemical, mechanical, optical and electronic properties. There is still no clear understanding of all possible consequences of miniaturization on the behavior of nanostructures. This thesis is focused on the analysis of mechanical and structural (including sputtering under irradiation) properties of nanorods. By nanorods we imply structures like beams or rods, with their cross-sectional diameter measuring in nanometers and having a length several times larger than the diameter. At such sizes it becomes possible to simulate the structures atom by atom using the molecular dynamics (MD) method. In the first part of the thesis, we analyze the elastic properties of Si nanorods: how the variation in size may change the elastic moduli, the effects of oxidation and intrinsic stresses. We also check the validity of the classical continuum mechanics approach by modeling the same nanorods with the finite elements method (FEM). In the second part we investigate sputtering from Au nanorods under ion irradiation. Recent experiments had shown that there is a big enhancement of sputtering yields from Au nanorods in contrast with those from a flat surface. The yields can be as much as 1000 per individual impact. MD gives us an opportunity to analyze the sputtering process with a femtosecond resolution which is impossible by any of the existing experimental methods. We find that an explosive ejection of nanoclusters is the main factor causing such large sputtering yields