The scientists at the Institute for Problems in Mechanical Engineering of the Russian Academy of Sciences, together with colleagues from other scientific organizations in St. Petersburg, found that when silicon carbide is grown on silicon in an innovative way previously discovered, silicon carbide nanotubes appear which are promising for use in lithium-ion batteries, carbon fiber materials, the automotive industry and medicine.

The results of the study are published in the journal "Physics and Technology of Semiconductors".

Nanomaterials are widely used in almost all fields of science, technology and everyday life. These are nanowires in microcircuits and quantum dots, for which the Nobel Prize was awarded in 2023 and which are widely used in the creation of color displays and other devices. Recently, they have been proposed to be used to create quantum computers. Nanomaterials are also widely used in biomedicine.

When carbon nanoparticles are added to various metals and alloys, hardness and strength of metals and alloys increase significantly. High-strength and wear-resistant materials are currently being created on the basis of nanomaterials. One of the varieties of nanomaterials is nanotubes. For example, single-wall carbon nanotubes are used in lithium-ion batteries, carbon fiber materials and the automotive industry. In acid-lead batteries, the addition of single-wall carbon nanotubes increases the number of battery recharge cycles significantly. Thus, in some studies it has been shown that replacing graphite, which is used as a negative electrode, with graphite with nanoscale silicon additives can increase the capacity of the negative electrode by more than 10 times.

The scientists of the IPMash RAS Laboratory of Structural and Phase Transformations in Condensed Media have been studying silicon-based nanomaterials for more than 20 years.  A fundamentally new way of monocrystalline silicon carbide cultivation on silicon has been created, which can lead to the creation of a new type of high-capacity electrodes.

The method resembles the «genetic synthesis» of protein structures in biology.

The quality of the structure of the layers obtained by this method exceeds significantly the quality of SiC films grown on silicon substrates by world’s leading companies. The method is cheap and technologically advanced.

«It turned out that during the synthesis of silicon carbide films by this method, not only highly perfect layers of silicon carbide are formed, which cover the silicon substrate from above, but arrays of nanotubes are formed under its surface, penetrating into the substrate depth for several microns» — Sergey Kukushkin, Head of the IPMash RAS Laboratory of Structural and Phase Transformations in Condensed Media, told.

He compared these nanotubes with the roots of plants. Further research showed that in this way a new method for producing nanotubes was discovered. With this growth mechanism, nanotubes grow «from top to bottom», unlike the standard method of growth of nanotubes and nanocrystals «from bottom to top». Studies have shown that these nanotubes can be separated from both silicon and the top layer of silicon carbide. 
The results obtained open up broad prospects for the relatively cheap production of arrays of SiC nanotubes, which can be used potentially for a number of instrument applications, for example, for various gas sensors and pick-ups.

In addition, the study of samples with human stem cells cultured on them showed that they do not produce a toxic effect.

According to Yulia Nashchekina, Senior Researcher, Head of the Tissue Engineering Group at the INC RAS, confocal microscopy data of mesenchymal stromal cells (type of stem cells), stained with rhodamine phalloidin to detect actin cytoskeleton and nuclear dye, demonstrated a sufficiently high affinity of cells with synthesized nanostructures. The cells adhered and spread out on the surface of the nanostructures, that is a partial confirmation of their biocompatibility with synthesized arrays of SiC nanotubes. This confirms the potential use of newly developed materials for the creation of various types of implants.

The study was carried out by the scientists from the Institute for Problems in Mechanical Engineering of the Russian Academy of Sciences together with colleagues from the St. Petersburg Electrotechnical University LETI (Laboratory of Micro- and Nanoelectronics), the University at the Interparliamentary Assembly of EurAsEC, the Institute of Cytology of the Russian Academy of Sciences with the financial support of the Scientific and Technical Center «New Technologies».