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Nanoelectronic devices
Published in David Crawley, Konstantin Nikolić, Michael Forshaw, 3D Nanoelectronic Computer Architecture and Implementation, 2020
Instead of a (gate) electric field, mechanical deformation can be used to modulate the molecular conductance. Transistor-like effects have been demonstrated in the case of the C60 molecule [48] and CNT [32], where a scanning tunnelling microscope (STM) tip has been used to compress molecules. If the deformation tool (e.g. the tip) is part of a piezoelectric element, then the mechanical action is controlled by an applied current which allows hybrid electromechanical circuits to be created. In principle, this type of device can operate at room temperature. The properties of small-scale and large-scale memory–logic circuits of such molecular electromechanical transistors have been analysed in theoretical simulations [49]. The main challenges with this technology are: high device leakage currents, problems with positioning molecules in nanojunctions and problems with the control of the position of the deformation tool.
Complexities of the Molecular Conductance Problem
Published in Sergey Edward Lyshevski, Nano and Molecular Electronics Handbook, 2018
Gil Speyer, Richard Akis, David K. Ferry
As a result, the most compelling conclusions indicated trends over large suites of similar systems. Complex bandstructure analysis confirms that, despite the increased distance between the contacts, certain nonplanar molecules can be expected to improve in conductance with stretching. The effect of vibrational modes on the coupling explains the higher conductance measured on a four-membered oligomer (quaterthiophene) compared to its three-membered counterpart (terthiophene). Stretching combined with the nuclear positions within a specific vibrational mode permit the interior rings of quaterthiophene to form a unique configuration which lowers the tunneling barrier for electrons. This configuration cannot be realized in terthiophene. These specific examples, however, cannot exhaustively describe the conductance properties of molecules. The individual molecular conductance calculation, deceptive in its apparent simplicity, requires the ability to treat the complexities of the contact, the extended states and work function of the metal, and the bandgap and bonds of the organic system.
Single molecule switch devices: A minireview
Published in Instrumentation Science & Technology, 2020
Yuanjing Li, Ke Xu, Xueyang Sun
Mei et al.[24] constructed a reversible and highly stable single-molecule switch based on diaryl ethylene. The structure of covalent graphene-diarylene was prepared and optimized by molecular engineering to reduce the coupling between the electrodes. Next, the transformations of open and closed molecular conformations under ultraviolet and visible light irradiation were analyzed, and graphene point contact arrays were prepared by damping line lithography (DLL). The experimental results showed that the effects of switching are essentially attributable to changes in molecular conductance, not only in the electron distribution of the molecule, but also in the energy level alignment between the electrode and the molecule.