Single-atom and single molecule electrical switches
Prof. Dr. Elke Scheer (Fachbereich Physik, Universität Konstanz)

The possibility to fabricate electronic devices with functional building blocks of atomic size is a major driving force of nanotechnology [1]. Key elements in microelectronics are reliable switches that can be operated as memories. Switches are usually realized by transistors and these components have been miniaturized all the way down close to the atomic scale. However, at such scales three terminals are technically challenging to implement. Therefore alternative control schemes like optical activation of molecules [2] or mechanical drives have been tested.
In this talk I will first present an experiment in which a metallic atomic-size contact has been operated as a reliable and fatigue-resistant two-terminal switch. Current pulses are used to toggle the conductance between two well-defined values in the range of a few conductance quanta. Due to its hysteretic behaviour with two distinct states, this two-terminal switch can be used as a non-volatile storage element [3].
At the end I will change gears and will briefly introduce photochromic molecules in use as active elements on optically driven molecular switches [4].

[1] R. Waser, Nanoelectronics and Information Technology, (Wiley-VCH, Weinheim, 2003).
[2] J. C. Cuevas, E. Scheer, Molecular Electronics: An Introduction to Theory and Experiment, (World Scientific Publishing, Singapore, 2010).
[3] C. Schirm et al, Nature Nano 8, 645, 2013.
[4] Y. Kim et al., Nano Lett. 12, 3736 (2012), Y. Kim, Phys. Rev. Lett. 109, 226801 (2012).