10:30am - 11:00amInvited
High Yield Molecular Junctions and Formation Dynamics Insights
1Swiss Federal Laboratories for Materials Science and Technology (EMPA), Switzerland; 2University of Basel, Switzerland
At the nanometer scale, molecular junctions represent a formidable test bed for investigating structure-function correlations in charge-transport phenomena. Assembling electronic, electro-mechanical or optoelectronic molecular devices opens the possibility to observe and eventually exploit quantum effects at room temperature. However, dynamic effects including changes in molecular conformation and variability in contact electrodes geometry, as well as a variation of the number of molecules in the junction, can result in different molecular signatures. These apparent difficulties have not prevented the development of organic electronic devices at the industrial scale, based on the assembly of molecular layers. Exploiting molecular properties and the intrinsic dynamics present in few or even single molecule(s) devices remains however a challenge to date due to the inherent stochastic behavior of molecular junctions.
This presentation will focus on the dynamics of molecular junctions and the possibility to achieve high junction formation yields at room temperature using directional binding groups. A series of experiments will be discussed that help unravel the microscopic details of the different molecular arrangements present in the junction, providing insights on how we may take advantage of dynamical rearrangements at the nanoscale to control molecular devices.
11:00am - 11:15amOral
Mechanically and Electrically Robust Self-Assembled Monolayers Based on Oligothiophenes
University of Groningen, The Netherlands
Understanding and controlling the electrical stability of self-assembled monolayers (SAMs) is of great importance on their utilization in electronic devices. Studies on the SAMs of alkane thiols have suggested a correlation between the robustness of the SAMs and the stability of their electrical behaviors. Thus, it is essential to consider the mechanical properties of the SAM in the rational design of the molecule. In this work, we engineer a particularly robust SAM of 4-([2,2’:5’,2”:5”,2”’-quaterthiophen]-5-yl)butane-1-thiol (T4C4) by linking oligothiophene with a short alkyl chain to enhance the intermolecular interaction. We form the metal-molecule-metal by placing a conductive AFM tip in stationary point contact with SAMs under a precisely controlled force load. The junctions are scanned under a bias from -1.5 V to 1.5 V with force load varying from 1.4 nN to 100 nN and I/V curves are transformed into log|I| for better interpretation. The SAM of T4C4 is mechanoelectrically stable, demonstrating the current at high bias almost unaffected up till a load of 25 nN. In comparison, the current from the SAM of C10 alkane thiol increases dramatically from a load of 1.4 nN to 10 nN, showing a less stable electrical behavior. Our study of the mechanical properties of the T4C4 SAM reveals its Young’s modulus is 5 folds higher than that of C10 alkane thiol SAM. Therefore, we conclude that oligothiophene-induced pi-pi interaction enhances the robustness of the SAM, giving rise to controllable electrical stability over a broad range of force loads.
11:15am - 11:45amInvited
Carbon Electrode-Molecule Junctions: A Reliable Platform for Molecular Electronics
College of Chemistry and Molecular Engineering, Peking University, China
This talk will exemplify our on-going interest and great effort in developing efficient lithographic methodologies capable of creating molecular electronic devices through the combination of top-down micro/nanofabrication with bottom-up molecular assembly. These devices use nanogapped carbon nanomaterials (such as single-walled carbon nanotubes (SWCNTs) and graphene) as point contacts formed by electron beam lithography and precise oxygen plasma etching. Through robust amide linkages, functional molecular bridges terminated with diamine moieties are covalently wired into the carboxylic acid-functionalized nanogaps to form stable carbon electrode-molecule junctions with desired functionalities. We have used these approaches to reveal the dependence of the charge transport of individual metallo-DNA duplexes on p-stacking integrity, and fabricate molecular devices capable of realizing label-free, real-time electrical detection of biological interactions at the single-event level, or switching their molecular conductance upon exposure to external stimuli, such as ion, pH and light.
 C. Jia, X. Guo, et al., Science, 352,1443 (2016).
 D. Xiang, X, Wang, C. Jia, T. Lee, X. Guo, Chem. Rev. 116, 4318 (2016).
 C. Jia, B. Ma, N. Xin, X. Guo, Acc. Chem. Res. 48, 2565 (2015).
 C. Jia, X. Guo, Chem. Soc. Rev., 42, 5642 (2013).
 X. Guo, Adv. Mater., 25, 3397 (2013).
 A. Feldmen, M. L. Steigerwald, X. Guo, C. Nuckolls, Acc. Chem. Res., 41, 1731 (2008).
 X. Guo, P. Kim, C. Nuckolls, et al., Science, 311, 356 (2006).
 Y. Cao, X. Guo, et al., Angew. Chem. Int. Ed. 51, 12228 (2012).
 C. Jia, X. Guo, et al., Angew. Chem. Int. Ed. 52, 8666 (2013).
 J. Wang, X. Guo, et al., Angew. Chem. Int. Ed. 53, 5038 (2014).
11:45am - 12:00pmOral
Nanoparticle-Molecule-Metal Junctions: A Scalable, Ambient Stable Strategy for Wafer-Scale Molecular Integration
1IBM Zurich Research Laboratory, Switzerland; 2Department of Chemistry, University of Basel, Switzerland
The ability to tailor an electronic component via the chemical structure of its molecular building blocks is the major motivation for research in molecular electronics. This concept promises increased functionality and novel device concepts which are scalable down to the single-molecule level. Implementing such electronic components, however, has proven to be difficult, especially in a way that is mass-fabrication compatible. In contrast to proof-of-principle single-molecule devices, such as diodes  or switches , a device based on a self-assembled molecular monolayer  does not require sub-nm lateral resolution. Here, we address the crucial issue of creating the top contact in a highly conductive, non-destructive and mass-fabrication compatible way by depositing a layer of metallic nanoparticles on the monolayer prior to top-contact evaporation. This strategy enables wafer scale fabrication of metal-molecule-metal junctions constrained into dielectric pores without suffering from issues such as metal filaments shorting the film or additional protective layers masking the molecular functionality. We benchmark this approach using alkanedithiols of different length, analyzing several thousand devices for each compound. Results demonstrate not only yields above 90% and excellent reproducibility for active areas ranging from thousands of μm2 down to thousands of nm2, but also reproduce the tunneling decay factor β found in literature, confirming that the approach does not mask the molecular functionality. The architecture can be used to upscale molecular integration and enable various applications ranging from electronics over photonics to sensing  or molecular compartments .
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