Experimental mechanics of suspended and supported graphene-based systems by Farzaneh BAHRAMI

For the degree of Doctor of Engineering Sciences and Technology

The high-quality two-dimensional (2D) crystals possess remarkable mechanical behaviour which offers exciting opportunities for new material selection and design, like the combination of extremely high in-plane stiffness and bending flexibility. For this reason, the nanomechanical testing of 2D layers and their 3D heterostructures is vital for proving their functionality in different applications. In this work, different nanomechanical testing including membrane deflection, nanoindentation and tensile have been performed with various techniques such as atomic force microscopy, nanoindentation and lab-on-chip developed in UCLouvain, respectively. By using these methods, the elastic and plastic behaviour of graphene as well as its effect on the mechanical response of copper thin film have been investigated. For each technique, some challenges are required to be faced and some uncertainties needed to be considered in order to extract the mechanical response precisely. Membrane deflection on single and bilayer graphene has been performed in order to extract Young’s modulus and fracture strength of these layers by considering the uncertainties and errors that can occur regarding the device calibration and experimental procedure. The effect of CVD-graphene on the plastic behaviour of Cu thin film in two different configurations has been investigated by nanoindentation in two different modes which are complementary to each other limitations. In this configuration, graphene acted as a perfect barrier against the movement and propagation of dislocations underneath the indent. In the last part, lab-on-chip (LOC) technique has been used to evaluate the effect of graphene on the fracture and creep behaviour of thin film of copper. Because of the limitations and challenges that are faced, there are no useful experimental results extracted in this section. However, a well-defined, adopted process for Cu/Gr specimens with Ni actuators has been proposed and the solutions for most of the challenges in each step are provided which make it easy for future investigations.

Jury members :

• Prof. Thomas Pardoen (UCLouvain, Belgium), supervisor
• Prof. Jean-Pierre Raskin (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Bernard Nysten (UCLouvain, Belgium)
• Prof. Jean-Christophe Charlier (UCLouvain, Belgium)
• Prof. Joris Everaerts (Materials Engineering, Belgium)
• Dr. Marc Verdier (SIMaP, France)

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