Abstract:
Two-dimensional (2D) materials are a unique class of atomically thin materials with a rich variety of electronic properties and potential applications in various fields such as nanoelectronics, energy harvesting, catalysis ... etc. To take full advantage of their potential, recent efforts are devoted to tailoring their properties by defect engineering or interfacial interactions. This seminar will cover recent achievements in tuning 2D materials, focusing on nitrogen doping of graphene and modulation of charge density waves in transition metal dichalcogenides (TMDs).
Graphene, a single layer of carbon atoms, exhibits Dirac Fermion physics due to its linear band dispersion. Nitrogen doping, where carbon atoms are replaced by nitrogen has garnered significant attention due to its potential to significantly tune the properties of graphene [1]. We have explored the impact of nitrogen doping on graphene using scanning tunneling microscopy (STM). Nitrogen doping induces n-type doping that can be exploited to achieve band engineering [2]. Nitrogen atoms also modify the local properties of graphene that can give it some chemical function, especially when combined to atomic vacancies [3]. These examples highlight the potential of defect engineering to tailor the properties of graphene and potentially 2D materials in general.
Layered transition metal dichalcogenides (TMDs) host a plethora of exotic ground
states such as superconductivity, Mott insulator, and charge density wave (CDW) states. Unlike 1D CDWs, their origins in 2D materials involve complex interactions, including q-dependent electron−phonon coupling or excitonic CDW. Beyond fundamental interest, CDW phase control has potential applications in oscillators and data storage. We will present recent experimental and theoretical results on the formation through alkali intercalation [4], and manipulation using a STM tip [5], of CDW phases in 2D materials. I will show how it is possible to induce transitions and to manipulate CDW phases, leading to potential applications.