Composite systems thin film-substrate
Materials deposited as thin films belong to the basic building blocks of micro and nanoelectromechanical systems. Thin films are withstanding mechanical loads in thermal actuators, whitches and capacitors in RF MEMS systems, optical switches, micromotors and many other miniature devices. One of the main criteria for the choice of materials for these applications is the ability to satisfy the requirement for certain mechanical properties, so that a good understanding of mechanical behavior of thin film materials is of a large importance (analysis of the process of creeping in thermal actuators, fatigue in polysilicon and metal microstructures, relaxation and creeping in switches made using aluminum or gold films, etc.
Electrochemical deposition is a technology useful for simple and controled formation of thin single- and multiple (composite) films for MEMS applications. Multilayer films or laminates are a subclass of thin films where strata of alternating different materials are deposited. By combination of different materials for substrates and films (Ni, Cu, Si) and optimization of process parameters we achieved a desired microstructure of films and to obtain a fine nanodimensional crystal granulation. It ensured tailoring of the desired improved mechanical properties of composite systems.
A test of sample deformation by an indented, due to a possibility to directly measure the indentation and to calculate hardness, as well as for the measurement simplicity, represents a very popular characterization method. To measure hardness of thin films one has to use very low loads, so that we talk about microindentation and nanoindentation. The method can be static, if one measures the indentation size after the process and calculates hardness, and dynamic, if one follows the dependence load-displacement of the indenter during the load-unload process. These data can be used to obtain parameters of the reduced model of elasticity and hardness.