Speaker
Description
Fine-tuning of applications based on 2D materials requires advanced characterization of their optical and electronic properties in conditions that are compatible with industry standards. While studies can be realized in free-standing conditions or at low temperature, identifying the contribution of the substrate in ambient conditions of laser processing are in high demand. Moreover, currently available optical measurements show some dependence on the chosen substrate. In these conditions, ab-initio modeling appears as an important path to gain knowledge for the development of applications.
In this work, we used the density functional tight-binding (DFTB) formalism to study the optical response of a flake of graphene deposited on a sample of quartz. After preparing the system with an optimal separation, the effect of lattice temperature on the optical response was estimated using an ensemble average of multiple configurations extracted from a quantum force-field (Born-Oppenheimer) molecular dynamics with a Nosé-Hoover thermostat. The computational results were compared with experimental measurements of transmission spectra, from 200 nm up to 2.5 µm, using a commercial monolayer graphene sample deposited on fused silica.
Beyond the role of shape and size of the flake on its optical response, it was found that its deposition on a quartz substrate can affect its Fermi energy and linear absorption spectra. Our computational protocol is a step forward in simulating challenging systems under realistic conditions, while providing intuitive insights for the design of nanoelectronic applications based on usage of organic 2D materials.