Organic electronics

The goal: tiny, efficient and environmentally friendly electronic devices. The medium: for precise staining of monomolecular layers

One of the ways to improve something is to "spoil" it a little. Thus, for example, steel is "contaminated" iron with a little carbon. The modern electronics industry developed and was established thanks to the ability to prepare semiconductors such as silicon (silicon) with such a high degree of purity that they can be contaminated ("salted") in a measured and controlled manner. It is the conduction that makes it possible to direct the movement of electrons through the semiconductor and thus control its electrical properties.
A team of scientists from the Weizmann Institute of Science, in collaboration with American scientists, recently succeeded in applying this process for the first time in the field of molecular electronics. The feasibility of developing molecular electronics based on organic materials stems from several advantages: first, there is a huge variety of organic molecules, and some of them are much cheaper than the semiconductors used today. Secondly, the organic materials are biodegradable - therefore they are more environmentally friendly. And thirdly, their flexible structure makes it possible to plan and make changes with relative ease, thus influencing the electrical properties of the devices that are composed of them. The main difficulties in the application of molecular electronics arise from the need to use sufficiently clean organic materials, as well as find effective ways to condense them.
Molecular electronics is one of the research approaches in organic material electronics and is based on single molecules, or layers, whose thickness does not exceed that of a single molecule. Prof. Yaakov Sagiv from the Department of Materials and Surface Research at the Weizmann Institute of Science, began conducting research on these layers about 25 years ago. For electronics, the problem is that these are delicate systems, which are difficult to handle precisely, and until recently it was not clear if it was even possible to filter them.
This is where Prof. David Kahn and post-doctoral researcher Dr. Oliver Seitz from the Department of Materials and Surfaces in the Faculty of Chemistry entered the picture, working in collaboration with Dr. Eilat Willan and Hagi Cohen from the Chemical Research Infrastructures Unit at the Weizmann Institute and Prof. Antwin Kahn, a visiting professor at the Institute from the University Princeton. With joint forces they managed to show for the first time that such scheduling is indeed possible.
The first step in the researchers' work was, therefore, to "clean" the layer of defects. The meticulous work of the ants included lengthy processes of drying, cleaning, removing oxygen and more. The researchers used a simple type of organic molecules, similar to the "octane" found in fuel, which are electrically isolated. Indeed, the electrical measurements showed that the electron current passing through the thin layer is similar to that passing through an ideal insulator. The result means that the system does indeed contain a certain, unavoidable level of defects, but these no longer dictate the behavior of the electrons.
Now that they had a clean system in their possession, the scientists began to "dirty" it, that is to say, to perform routing. To do this they irradiated the surface with ultraviolet light or a weak electron beam. As a result, there was a chemical change in the composition of the carbon chains that make up the molecular layer, and double bonds were formed between the carbon atoms. These bonds affect the movement of electrons through the molecules.

Prof. Kahn: "The method we developed makes it possible to start the work with a system that behaves as an ideal, in which there is a sufficiently uniform layer of molecules, which (and not the defects) dictate the nature of the passage of electrons through the layer. Once such an ideal system exists, it can be changed according to needs through routing, thus controlling the properties of electrical transmission." The new method was recently described in the Scientific Journal of the American Chemical Society. The scientists say it will make it possible to significantly expand the use of monomolecular organic layers in the field of nanoelectronics. Dr. Seitz: "If one is allowed to be very optimistic, and to dream a little, it may be that with this method it will be possible to create tiny, different, and perhaps more environmentally friendly electrical devices, compared to the devices that exist today."