A method developed at the Weizmann Institute makes it possible to produce chemical nanoprints in a huge range of dimensions - from nano to macro, using an electron beam aimed at pre-defined surface areas
Given the fact that we cannot shrink ourselves to the size of a molecule or an atom, how will we enter the gates of the promised land of the smallest devices - the nanodevices? Such tiny devices, with enormous data capacity and other exciting possibilities, are indeed the promise of the future, but integrating them into the big world in which we live is a significant challenge. Weizmann Institute scientists have recently developed a new method that may bridge the gaping chasm between the big world (the macro) and the tiny world (the nano) through chemical printing.
The beginning of the project was a surprising observation in the laboratory of Prof. Yaakov Segiv in the Department of Materials and Surfaces. As part of experiments on layered molecular structures, faculty scientist Dr. Rebecca Maoz exposed to an electron beam a structure consisting of a silicon substrate coated with a single layer (a self-assembled layer with a thickness of one molecule) of a soap-like substance, and on top of that a thin layer of a polymer containing oxygen. Under normal conditions, the polymer layer easily peels off from the underlying monolayer, but after exposure to the electron beam, the two layers remained stuck together. The scientists found an explanation for the unexpected discovery: the exposure to the electron beam led to a chemical change on the surface of the monolayer as a result of an oxidation reaction in the seam between the two layers and the polymer layer.
As reported in the scientific journal ACS Nano, the team of researchers, which also included Dr. Jonathan Berson, Dr. Doron Burstein, Dr. Peter Nelson and Ariel Singer from the Department of Materials and Surfaces, and Dr. Ora Beaton from the Department of Chemical Research Infrastructures, developed Based on the discovery of an innovative method for creating nanoprints. Within this method, an electron beam is directed to pre-defined areas of a surface and is used to create extremely tiny chemical prints on the surface. Precise control of the direction of the electron beam, using equipment designed for this purpose, allowed the scientists to produce complex prints on the surface of the monolayer. The tiny prints created by this process could be identified and observed using an atomic force microscope.
The scientists even found that this is not a special case of the same polymer, and that thin layers of additional materials, including metals, can be used as a catalyst for chemical changes using an electron beam. Later it also became clear that additional chemical changes can occur in a similar process over different types of surfaces. These findings indicate that the developed method has a wide potential for creating chemical nanoimprints for various purposes. For example, this is how it is possible to produce a new type of molecular-thick electronic circuits, in which electric current-conducting surface tracks are isolated from each other by means of non-conducting regions.
Creating controlled chemical changes in selected areas of the outer layer of atoms on the surface of a solid material - without causing changes in nearby areas or in deeper layers - is a completely new approach to creating nanoprints, and it has unique advantages. The existing methods for creating nanoprints using an electron beam work in one of two approaches: destructive processes in which they "dig" inside the material, or alternatively, processes in which other materials are added to the surface of a given material. In both cases, in the process, structural defects are inevitably created in the seam between different areas of the print. In contrast, the chemical method developed is non-invasive and non-destructive; It enables the creation of flawless area prints, without "seams" between different areas of the print - an important advantage in many applications, and especially essential in the creation of electronic circuits.
Equally important: other methods for creating nanoprints operate only in the nanoscale. This means that additional technologies are required to connect nanodevices produced by these methods to the macro world. Creating these types of connections poses difficult technological challenges, and their mere presence can lead to multiple failures. With the new chemical method, on the other hand, it is possible to produce prints in a huge range of dimensions, from nano to macro, so that the same technology can successfully bridge the two worlds.
