טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentYaniv Rotem
SubjectRobust Lubricity of Gold-Graphite Heterointerfaces
DepartmentDepartment of Materials Science and Engineering
Supervisor Dr. Elad Koren
Full Thesis textFull thesis text - English Version


Abstract

2-Dimensional (2D) materials are crystalline materials consisting up to few layers of atoms, characterized by unique mechanical, optical and electrical properties. Thus, 2D materials hold great promise to numerous applications in various fields, such as condensed matter physics, material science and nanotechnology, and have been studied vastly in recent years.

One of the most intriguing properties of 2D materials is structural lubricity, a phenomenon in which the resistance to sliding vanishes or nearly vanishes, due to extremnely low friction between the sliding crystals. Though numerous studies reported observations of structural lubricity, the reasoning behind the occurance of this phenomenon is still lacking, which  essentially prevents the realization of robust structural lubricity.

Non-commensurate two-dimensional interfaces hold great promise towards low friction and nanoelectromechanical applications. For identical constituents, the crystals interlock at specific rotational configurations leading to high barriers for slide. In contrast, non-identical constituents comprising different lattice parameters should enable robust superlubricity for all rotational configurations, as truly commensurate orientations are not possible because of the lattice mismatch. This is however not the case for gold-graphite interfaces, as both theory and experiments show scaling behavior of the sliding force as a function of the interface contact area.

In this work, we use numerical simulations in order to study the friction force behavior of gold crystals on graphene sheets, as function of the misfit angle between the lattices and the geometry of the sliding crystals. We show that the origin for high force barrier at special angular configurations is a result of commensurability between the moiré structure of the force landscape and the contact geometry. Consequently, this thesis suggests new geometries that can potentially overcome such commensurability effects to enable robust superlubricity.