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 doors for creating new materials with specified properties at the atomic level. Such methods are particularly 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 material analysis has been developed by scientists from the A. V. Rzhanov Institute of Semiconductor Physics SB RAS. Such precision 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 surveillance, 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 a force of interaction with the surface, this affects the frequency and phase of the probe's oscillation. By analyzing these data, it is possible to recreate the relief of the material and its properties in detail.
To also determine 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 cluster of metal 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 "gap" plasmon coincides with the excitation energy in the material, light scattering is significantly enhanced. This allows obtaining 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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