The synthesis and characterization of graphene-copper heterostructures and investigation of their heat dissipation performances

In today's technology, heat spreaders, made from materials with high thermal conductivity values (e.g. copper), play important role in removing the heat generated within the microprocessor (CPU). However, these materials quickly became inefficient to dissipate the ever increased heat loads, hence novel alternative materials, with higher dissipation efficiency are required. In this thesis, the aim is to develop a novel heat spreader capable of effectively using its entire area for heat dissipation. In this context, the graphene-copper heterostructures' designs are proposed. For this, firstly the formation of graphene on copper foil is studied. The effects of the major processing parameters and the mechanisms were investigated. Hence the graphene synthesis on copper foil was optimized for the further graphene-copper laminate structures. After the optimizations, the thermal properties of graphene-copper laminates and copper laminates are investigated by both the computational methods and experimental thermal measurements. These studies showed that the presence of graphene failed to contibute to the thermal conductivity of overall laminate structure. It was understood that the graphene in graphene-copper laminate structure was too thin compared to the copper layer in the system to achieve the expected increase in thermal conduction. Thus, in the light of the results obtained from the studies, graphene-copper porous structure is proposed. The graphene-copper porous structure synthesis and characterization were studied in detail and thermal measurements were carried out. The thermal diffusivity performance of the structure with graphene has been shown to increase. This positive effect of graphene on thermal properties is explained by the high thermal diffusivity of graphene as well as its protection of copper from oxidation. Finally, to increase the growth surface area of graphene, the addition of graphene oxide (GO) which is synthesized via Tour method is used as a stopping mechanism for the sintering behaviour of copper powders. However, the increased amount of GO created more porosity which results in loss of heat dissipation that could not be matched by the increased amount of the graphene's contribution to heat dissipation, resulting in a decrease in the overall thermal diffusivity.