Molecular building blocks
Transport through single components
We design single molecules, metallic nanoparticles, DNA based structures, polymers or silicon nanowires to be used as basic functional building blocks for more complex microelectronic systems. To understand the transport characteristics of the designed functional units, we use experimental techniques, such as scanning tunneling microscopy (STM) at low temperature and mechanically controllable break-junctions (MCBJ). The conductance properties of the building blocks are also investigated using different (conventional and non-conventional) contacting techniques and the resulting structures are explored for potential future devices. Experimental electrical characterization is always accompanied by theoretical modeling to gain in-depth knowledge of transport properties of single nanocomponents.
Organic molecules enable the design of atomically controllable electronic functionalities. One of the research projects of the IHRS NanoNet consists in demonstrating light-induced switching of isolated molecules on insulating surfaces. The switching of molecular states is often accompanied by conformational changes in single molecules. The mechanism leading to such conformational changes can be studied by STM at low temperature. Although STM can reveal the nature of molecular orbitals, it cannot give insights into transport phenomena through a molecule placed between two conducting contacts and bound in a stable geometry unless very specific geometries are tested. The electrical characteristics of the switches are thus investigated using the MCBJ technique, in which a molecule is connected repeatedly between the two metallic tips. With this setup, one can measure the difference in conductance between two molecular states.
We design and synthesize conducting polymers for a wide range of uses in nanoelectronic circuits. When considering the use of molecular structures as active electronic components, such as memory elements or amplifiers, and molecular wires, i.e. direct connects between active components, the understanding of conduction mechanisms along single molecules at various length scales becomes essential. For this purpose we use MCBJ setups for molecular structures up to 5 nm length, and electrodes which are produced by direct lithography, or shadow mask evaporation for longer molecules, or larger molecular assemblies.
Metallic magnetic nanoparticles offer the possibility to use various magnetoelectric effects on the nanoscale. They can also be used to build up larger structures with well-defined magnetic properties and serve as templates for the creation of ordered nanoparticle arrays. Such larger structures can then be used as memory elements. While the storage and switching mechanisms for such memory elements are well known, their integration into large-scale circuits has not yet been achieved. One of our aims is to study methods to self-assemble (magnetic) nanoparticles, to interconnect (magnetic) nanostructures, and to couple them to organic electronics.