Classically a nanowire with a length larger than its circumference is expected to be unstable due to Rayleigh instability that appears in specimens with large aspect ratio. In contrast we present... Show moreClassically a nanowire with a length larger than its circumference is expected to be unstable due to Rayleigh instability that appears in specimens with large aspect ratio. In contrast we present experimental evidence that metallic nanowires with thicknesses ranging from one atom to hundreds of atoms present two series of exceptionally stable diameters, well determined and reproducible. The two series of stable diameters can be described in terms of shell closure effects. For low diameters the stability is given by the confinement of the electronic orbits in the nanowire cross-section, which is an electronic shell effect. Thicker nanowires are stable for densely packed structures, related to minima in the surface energy, which we refer to as atomic shell effect. A significant part of this thesis is dedicated to the study of shell effects for different types of metals: the monovalent noble metals, and multivalent Al and Mg. Additionally we investigate the stability from a mechanical point of view by measuring the stiffness of atomic contacts. The last chapter is dedicated to electrochemical methods of nanowire fabrication and we explore possible ways of enhancing the nanowire stability. Show less
