"If one is allowed to dream, it may be that with this method it will be possible to create tiny, efficient and environmentally friendly electrical devices" say researchers at the Weizmann Institute who have discovered a method for developing unique nanometer materials
From the right: Dr. Ayelet Willan, Prof. David Kahn, Dr. Oliver Seitz and Prof. Antwin Kahn. double bonds
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 made of silicon (silicon) with such a high degree of purity that they can be polluted ("salted") in a measured and controlled manner. The concept of infection is taken from the world of microbiology, where it refers to infection with bacteria or a contaminating disease. Materials researchers carry out the plating process by introducing a tiny amount of foreign atoms, such as phosphorus atoms, into the mold. It is the conduction that makes it possible to direct the movement of electrons through the semiconductor, thus controlling its electrical properties. This is a phenomenon similar to what happens when an empty chair is added to a circle of seated people - something that allows a constant "flow" of people to the empty (changing) chair. A similar phenomenon occurs when a person who enters a circle of empty seats begins to move and move from chair to chair.
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 developing field of organic electronics. The idea to replace the form in the electrical components with molecules and organic polymers was born about five decades ago. This is a worthwhile idea in various respects: there is a huge variety of organic molecules, and some of them are much cheaper than the semiconductors that are used today; The organic materials are biodegradable - therefore they are more environmentally friendly; And their flexible structure makes it possible to design 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 - as was done in the processes of preparing electronic devices made of tin.
One of the research approaches in working with organic materials is to test the electrical properties of individual molecules, or thin layers, whose thickness does not exceed that of a single molecule. Prof. Yaakov Segiv, from the Department of Materials and Surface Research at the Weizmann Institute of Science, began conducting modern research on monomolecular organic layers about 25 years ago. Today, many scientists from different parts of the world work in this field of research. These are delicate systems, which pile many difficulties on the way of the researchers, since it is difficult to install them for the purpose of making the electronic measurements without harming their integrity. Another difficulty arises from the fact, dictated by the laws of thermodynamics, that these thin layers contain defects. These defects, which affect the passage of the electron current, can dictate the results of the electrical measurements - a problem that until recently was the Achilles' heel of the field. In addition to this, the possibility of filtering unimolecular organic systems and the meaning of the process were in doubt.
This is where Prof. David Kahan and post-doctoral researcher Dr. Oliver Seitz from the Department of Materials and Surfaces in the Faculty of Chemistry came into the picture, working in collaboration with Dr. Eilat Vilan and Dr. Hagai Cohen from the Chemical Research Infrastructures Unit at the Weizmann Institute of Science, and with Prof. Antwin Kahn, Visiting professor at the institute, from Princeton University. With joint forces they were able 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 optically isolated
tram. Indeed, the electrical measurements showed that the electron current passing through the thin layer is similar to that passing through an ideal insulator. The meaning of the result is 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 organic molecules.
Prof. Kahn: "The method we developed makes it possible to start the work with a system that behaves as ideal, in which there is a sufficiently uniform layer of organic molecules, which (and not the defects) dictate the nature of the passage of electrons in the material. Once such an ideal system exists, it can be changed according to needs through routing, thus controlling the properties of the electrical transmission." The new method was recently described in the Scientific Journal of the American Chemical Society.
The scientists say that 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, maybe with this method it will be possible to create tiny, different electrical devices, and perhaps also more environmentally friendly, compared to the devices that exist today."
