Study of the mechanical properties of Cu-graphene multilayered structure and its large-scale fabrication process

Abstract

Carbon based materials are being recognized as the future of composite materials, especially as metal-carbon composites that demonstrate enhanced mechanical properties compared to metals. The conventional method for synthesizing such metal-carbon composites is to create a simple, random mixture. However, as the volumetric content of carbon materials is increased beyond a critical point, the random rule of mixture does not guarantee a homogenous dispersion, which sets limit on the strengthening potential. On the contrary, nano-layered multilayer structures are much more efficient in suppressing the dislocation movement across their interfaces and thus have larger potential for strength enhancement. In addition, it is shown that as the layer dimension decreases in such multilayer structure, higher strength is expected. Metal thin films are much stronger than bulk metals and when they are stacked together to form multilayer, ultrahigh strength can be observed. Previous reports developed Cu- or Ni- graphene multilayered composite designs to achieve ultrahigh strengths. The previous methods for fabricating metal-graphene multilayer included polymer based graphene transfer and vacuum based metal deposition processes, both of which would inevitably inflict limits for continuous larger scale production. In chapter 2 and 3, a new method of graphene transfer applicable to larger scale roll based dry graphene transfer and electroplating of metal layers for faster and efficient deposition is introduced. Prepared metal-graphene composite structure is tested by nano-pillar indentation method to measure the enhanced mechanical properties. In chapter 4, patterning process of Cu-graphene multilayer structure for possible application on flexible electrode material is introduced. Conventional lithography patterning process in semi-conductor manufacture includes photoresist masking and light-exposure or heat treatment process. This process contains several limiting factors for continues and larger area patterning. Thus, in this chapter, stamp patterning process is introduced and possible obstacles for applying it to real production are discussed.