• Hammad, Mohamed
• Raskin, Jean-Pierre
• Idrissi, Hosni
• Nysten, Bernard
• Bahrami, Farzaneh
• Fivel, Marc
• Dhaese, Cécile
• Ding, Lipeng
• Pardoen, Thomas
• Huet, Benjamin

Abstract

This research is investigated the effect of the presence of a single layer graphene on the development of thecontact plasticity inside a copper underlying substrate. As a matter of fact, a film of copper (deposited on a Siwafer) is the substrate used in the CVD process for graphene production, there is no need for transferringgraphene which avoids any possible artifacts. Moreover, the adhesion between CVD-grown graphene and theunderlying Cu film is larger than transferred graphene, since during transfer, wrinkles and ripples may form, thusweakening the interaction between graphene and the substrate. The bare Cu-film in the same condition as toproduce graphene except that no methane was introduced into the chamber (the last step in grapheneproduction). Nanoindentation was performed on the Cu-film with and without graphene. Nanoindentation wasperformed on the bare Cu-film also Cu-film with graphene. The same process, as the growth of graphene onCu-film, was performed on bare Cu just without introducing the methane flow at the last step. The analysis of theforce-displacement curves indicates that the presence of graphene modifies the onset of plasticity whichappears in the form of a burst which is called pop-in. The first pop-in occurs at lower loads and the pop-inlengths are smaller with graphene in comparison to the bare Cu-film. The magnitude of the effect of thepresence of a graphene cap layer varies also with respect to the orientation of the indented Cu grain. In order tounderstand the root causes of these effects of the presence of graphene on the plastic flow, transmissionelectron microscopy is used to compare samples after nanoindentation in terms of dislocation structures. 3Ddiscrete dislocation dynamics simulations are performed to analyze the long-range back stress that aregenerated by the dislocation arrangements with and without graphene. To further extend this research andinvestigate the known effect of hardening by graphene insertion into metals, another system has beenaddressed which involves the deposition of a Cu film on top of the graphene layer, lying itself on top of theannealed Cu substrate. The presence of graphene caused marked effect on the indentation response in thiscase, even larger than in the first configuration.

Topics

• impedance spectroscopy
• polymer
• grain
• simulation
• nanoindentation
• dislocation
• copper
• plasticity
• chemical vapor deposition
• microscopy
• dislocation dynamics