Russian researchers have developed a new method for analyzing nanostructures. It expands the capabilities of modern atomic force microscopes and allows studying materials at the level of individual nanometers. This technology opens the door to the creation of new materials with specified properties at the atomic level. Such methods are especially relevant for the development of future electronics. For example, they can be used to create microscopic sensors and molecular robots.
A new ultra-precise spectral optical method for analyzing materials has been developed by scientists from the A. V. Rzhanov Institute of Semiconductor Physics SB RAS. Such accuracy is necessary for creating miniature devices and technologies. For example, it is needed in molecular robotics for the precise delivery of drugs in the body, in sensor-"dust particles" for monitoring objects and inconspicuous observation, as well as in insect drones capable of exploring spaces and surfaces inaccessible to humans.
One of the methods for studying nanostructures is Raman spectroscopy. It consists of analyzing the spectrum of laser radiation reflected from the structure under study. This radiation, like fingerprints, contains all the information - from the composition of the substance and impurities to various defects, deformations and stresses.
Atomic force microscopes work as follows: an oscillating probe, a needle with a tip of only 50 nanometers, approaches the material. When the needle encounters an interaction force with the surface, this affects the frequency and phase of the probe's oscillation. By analyzing these data, it is possible to recreate in detail the relief of the material and its properties.
In order to determine also the spectral characteristics of the material (for example, the chemical composition at each point), we apply silver, gold or platinum to the probe in such a way that one metal cluster with a size of about 100 nm is formed on its tip. A strong electric field is formed under it in a small area. On the other hand, we used arrays of gold nanodisks as a substrate for the structures under study.
According to him, when a metallized probe approaches gold nanodisks, a hot spot - a plasmon - arises between them. This is an area with a high intensity of electromagnetic field.
When the energy of the "slit" plasmon coincides with the excitation energy in the material, the scattering of light is significantly enhanced. This allows to obtain more accurate data. The researchers sought to create conditions for such an effect. As a result, they achieved a signal amplification of 100 thousand times with a spatial resolution of 2 nanometers.
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