Nanomechanics and Micromechanics of Thin Films, Graded Coatings, and Mechanical/Nonmechanical Systems

Abstract

A broad classification of small-volume systems is presented in terms of partially or fully confined one-dimensional structures (e.g. unpassivated and passivated thin films on substrates), two-dimensional structures (e.g. unpassivated and passivated patterned metal interconnect lines on substrates used in integrated circuits), and three-dimensional structures (e.g. passivated and unpassivated islands used in micro-electromechanical systems or MEMS). In each of these systems, different possibilities involving uniform and spatially graded compositions, and purely mechanical loading or electrical/mechanical coupling, are considered. On the basis of this definition of small-volume structures, an overview of recent advances in our understanding of nano/micromechanics is provided. The effects of microstructural and geometric length scales on deformation are then examined in these geometries (e.g. Wikstrom et al. 1999a, 1999b; Gouldstone et al. 2000). A wide range of experimental tools for probing nanomechanical properties is considered, with a particular emphasis on depth-sensing indentation as a vehicle for probing nanomechanical deformation mechanisms. Mechanical measurements are then combined with detailed observations in the transmission electron microscope to extract the conditions governing discrete and continuous deformation phenomena that occur at the nano-size scale (Gouldstone et al. 2000). The effects of electrical and magnetic coupling on deformation are then addressed, with specific references to applications involving piezoelectric materials and magnetic information storage systems (e.g. Giannakopoulos and Suresh 1999). New methods are described for the characterization of electrical active surfaces with nanomechanical probes (Ramamurty et al. 1999, Sridhar et al. 2000). The presentation concludes with a discussion of novel strategies for compositional gradation for the protection of surfaces for contact damage for biomechanical and structural coatings (e.g. Jitcharoen et al. 1998, Suresh and Giannakopoulos 1990).