Crystalline nano-objects: from fabrication to mechanical properties

International audienceThe interpretation of experimental results in terms of mechanical properties generally requires to build a model representing the actual object. In this introductory chapter, we intend to show why in this approach, it is necessary to keep in mind that actual nanoobjects, as they exist in functional devices, do not a priori obey to an ideal model. Theissue we would like to emphasize here is that nano-objects result from complex fabrication methods (physical growth, chemical synthesis, etching, lithography…) which make them by nature different from simple pieces of bulk bounded by a surface or an interface. Internal stresses and elastic properties are intimately related to the structureand the chemistry, which are rarely fully characterized. Also the nature and density of defects controlling the plasticity are strongly impacted by the fabrication method. Finally, let us note that the experimental studies of mechanical properties are most often conducted on nano-objects which have been specifically fabricated for this purpose andare somewhat simplified compared to those actually present in functional devices.This introductory chapter will address these issues by the means of some examples of nano-objects milled from bulk (nanopillars) as well as self-assembled (thin films, nanowires, nanoparticles…). After a brief recall on mechanical properties definition (section 1), section 2 will present some examples of the strong link between structural properties, internal stresses and the fabrication techniques. Section 3 discusses some issues encountered in internal stress and strain measurement in the specific context of nano-objects. Finally a temporary and non exhaustive review of size effects on mechanical properties is proposed in section 4. The main objective of this introductory chapter is to underline that size effects should be examined in the context of fabrication methods. For more details on an experimental technique or a physical issue, the reader is invited to refer to specific chapters