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[交流] 巴黎西岱大学(巴黎七大)Dr. Xiaonan SUN课题组招2025CSC博士生

巴黎西岱大学(巴黎七大)Dr. Xiaonan SUN课题组招2025CSC博士生
研究单位：界面处理组织和系统动力学实验室（ITODYS）
要求：化学或者物理化学背景，2024年7月份取得硕士学位，最好有托福或雅思成绩，CSC（公派）项目留学生。
课题主要方向是分子电子学，仪器涉及扫描隧道显微镜（STM），原子力显微镜（AFM），电化学工作站等。如有意向望尽快邮件导师Dr. Xiaonan Sun。Dr. Xiaonan Sun教授是个专注于科研的老师，平易近人，科研成果较好，在J. Am. Chem. Soc.和Nano Letter, Nanoscale, JPCL等学术杂志上发表多篇文章。

导师认真负责，关心留学生，不论在科研还是生活都给了大家很多帮助，对想出国读博的同学是很好的机会。

联系方式：Xiaonan Sun: sun.xiaonan@u-paris.fr

详细官方研究计划如下，同时欢迎邮件咨询。

Title: Charge transport properties of single molecular junctions
Keywords: Charge transport properties, single molecule junction, Scanning tunneling microscope, diazonium reduction, conductance switching
Type de financement demandé : 4 ans de thèse

Equipe d’accueil : équipe nanoelectrochimie –ITODYS, UMR 7086, Université Paris Cité (Paris 7) Pôle : Sciences Exactes et Technologie / Exact Sciences and Technology
Ecole doctorale : ED 388 - Chimie Physique et Chimie Analytique de Paris-Centre Langue de Travail : Anglais
Direction : Dr. Xiaonan Sun

Contact email: sun.xiaonan@u-paris.fr

Project:

The basic component of molecular devices is a molecular junction and the continuous downsizing of electrodes to a limit of 10 nm emphasizes the need for stable junctions at the single molecule level. As a result, the study of the transport properties of single molecular junctions (SMJ) has attracted broad and significant research interests in the past decades. In this respect, scanning tunneling microscopy break junction technique (STM-bj) will be used to construct and to study the charge transport properties and functionalities for future molecular memory and diode, the proposed phd project will mainly focus on the following points:
Part I: The conductivity will be studied by STM-bj with the target to improve their stability

Functional molecules with active anchoring groups are selected in investigating the single molecular junctions. STM-based break junction (BJ) measurements will be performed where STM tip will be controlled to crash on molecule decorated the surface and to pull-out the metal-molecule-metal junctions. Conductance-vs-extension (I(d)) curves will be extracted while pulling-out the junctions and will allow the measurements of the conductance of a
single molecule.[1,2] The phd project will be to improve the SMJ stability, an important strategy is to step-wise modify the molecule/electrode contacts[3-4] from weak to strong. Rigid porphyrin-based SMJs will be built and compared with: weak top/molecule and strong covalent molecule/bottom contacts (C-Au or C-C bindings); and double covalent molecule/electrodes contacts. The life time of the SMJ is expected to be largely improved 5 (into
minutes or hours) and the electric contacts to be optimized for a better performance of the junctions. The result of Part I will provide well-define method to achieve very stable SMJ for the following functionality characterization.

Part II: SMJs with functionalities for memory

The formation and the conductance measurement of SMJs with potential applicable functionalities for real-life devices are essential. Multi-states molecules [6-7] are appealing candidates for the design of molecular devices, such as for storage. The selected molecules which have not only multiple well-defined and stable states with distinctively tunable electronic properties [8-12], but can also and more importantly, be switched by different means such as light, heat or electrical stimulation. The target molecules
will be then appropriately connected inside a SMJ (using the methods achieved in part I). Single molecule hysteretic I/V loops will be a direct proof of electric field generated SMJ conductance switching. A few factors such as the junction length, the modification of central molecular core with extra redox-active units are foreseen to involve multi states conductance switches and are hence expected to give high ON/OFF ratios above 1000. Overall, the ultimate and essential goal of the phd project is to build super-stable, multi-switchable SMJs with electric field generated conductance switching with high ON/OFF ratio for developing storage devices.
Main teams of the field: The main teams of charge transport properties of single molecule junctions are: (i) I. Díez-Pérez, Department of Chemistry, University of King’s College London, England (ii) L.Venkataraman, Columbia University, USA (iii) H. Van der Zant, Delft University of Technology, the Netherlands (iv) W. J. Hong, Xiaoment University, China
The PI of this project is expert on charge transport properties of single molecule junction and on Scanning tunneling microscopy to image molecular reactivities on surface. Using the experiences of the PI, two main target including the improvement of SMJ stability and the investigation of single molecule conductance switching will be mainly investigated. The scientific results can be used for the optimization of single molecule-based devices such as memory or storage.
[1] B. Xu, N. J. Tao, Science 301, 1221-1223 (2003).
[2] D. Xiang, X. Guo, et. al. Chem. Rev., 116, 4318 (2016).
[3] V. Q. Nguyen, X. Sun, F. Lafolet, F. F. Audibert; F. Miomandre, G. Lemercier, F. Loiseau, J. C. Lacroix, J. Am. Chem. Soc. 138, 9381 (2016).
[4] X. Yao, X. Sun*, F. Lafolet, J.C. Lacroix, Nano Lett. 20, 6899 (2020).
[5] X. Yao, X. Sun*, J. Weiss, J.-C. Lacroix et al. Nano Lett. 21, 6540 (2021)
[6] I. Hnid, X. Sun*, D. Frath, F. Lafolet, J. C. Lacroix, Nanoscale 11, 23042 (2019)
[7] I. Hnid, L. Guan, E. Chatir, S. Cobo, F. Lafolet, F. Maurel, JC. Lacroix, X. Sun*, Nanomaterials 12 (8), 1318 (2022)
[8] Q. V. Nguyen, P. Martin, D. Frath, M. L. Della Rocca, F. Lafolet, C. Barraud, P. Lafarge, V. Mukundan, D. James, R.L McCreery, J. C. Lacroix, J. Am. Chem. Soc. 139 , 11913(2017).
[9] I. Hnid, D.Frath, F. Lafolet, X. Sun, J. C. Lacroix, J. Am. Chem. Soc. 142 7732(2020).
[10] Q. V. Nguyen, P. Martin, D. Frath, M.L. Della Rocca, F. Lafolet, S. Bellinck, P. Lafarge, J.C. Lacroix*, J. Am. Chem. Soc. 140,10131(2018).
[11] I. Hnid, M. Liu, D. Frath, S. Bellynck, F. Lafolet, X. Sun*, J.C. Lacroix , Nano Letters 21 (18), 7555 (2021).

[12] X. Yao, M. Vonesch, M. Combes, J. Weiss, X. Sun*, and J. C. Lacroix. Single-Molecule Junctions with Highly Improved Stability. J. Mate. Chem. C, 12 (12), 4326 (2024).

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