- Time: 15:00
- Date: April 18, 2022
- Venue: https://xjtlu.zhumu.com/j/621208203
- Meeting ID: 621 208 203
- Speaker: Dr. Yannick J. Dappe
- Topic: A model molecular transistor: some theoretical perspectives
Molecular Electronics is a field of science, which studies the electronic propagation across a molecular system connected to electrodes under an applied bias. As such, this is an interdisciplinary field, ranging from fundamental research to applications, like molecular electronic devices for example. In order to design such a device, it is necessary to understand the electronic transport through a single molecule, to fabricate a single molecular junction and to probe the corresponding electronic response to try to mimic standard silicon electronic devices like diodes or transistors.
In this seminar, I will present a model molecular transistor based on a redox active viologen molecular bridge between a gold and a graphene electrode. This system has been studied experimentally in an electrochemical gating configuration in an ionic liguid medium. The corresponding measured conductance clearly exhibits the typical on/off response of a standard transistor. The experimental data is compared against two theoretical models, namely a phase coherent tunneling and an incoherent "hopping'model. The former is a simple gating monoelectronic model within density functional theory (DFT) which discloses the charge state evolution of the molecule with electrode potential, The latter model is the collective Kuznetsoy UIstrup (KU) model for 2-step sequential charge transport through the redox centre in the adiabatic limit. The comparison of both models to the experimental data is discussed here for the first time.
By comparing to, and achieving apparently reasonable fits to both models, we are presenting a challenge to the community to compare fits to divergent models and hopefully then discover future ways experimental or theoretical, to distinguish between them in such systems.
Sh.Tao et al, Phys.Chem. Chem.P
Y.J.Dappe,Applied Sciences 10,6162 (2020).
Q.Zhang et al, Nano Letters 16,6534(2016).
Yannick J.Dappe obtained his PhD at Strasbourg University in 2002 on the theory of nonlinear optics on metallic surfaces. He went to the group of Prof.F. Flores at the Autonomous University in Madrid (2004-2008) to learn Density functional Theory (DFT) methods and developed expertise in theory of van der Waals interactions in graphene and carbon materials,and electronic properties of molecules on surfaces. Since 2008, he is CNRS researcher, now at the Condensed Matter Physics Laboratory (SPEC) of the CEA Saclay. His main research interests focus on the theoretical study of graphene, 2D materials and van der Waals heterostructures, electronic transport in nanostructures, STM image simulations and Molecular Electronics, using DFT and Keldysh-Green methods. He has published around 110 articles in scientific journals for around 2500 citations and a h-factor of 27. Since 2015. he established a strong collaboration with the group of Dr, Li Yang at XTLU Chemistry Department, leading to several publications and projects in the field of Molecular Electronics, and the co-supervision of 4 PhD students. He is also Honorary Lecturer in the same department since July 2019.