Scientists reveal the secret of the material for promising infrared cameras

Bolometer. Credit: Daria Sokol / MIPT

Researchers at the Moscow Institute of Physics and Technology and the RAS Institute for Theoretical and Applied Electromagnetics have discovered that vanadium dioxide films produce electricity. published in Physical Review B, Their findings will enable thermal imaging devices with better sensitivity and response rates than currently existing analogs.

While 100-nanometer thin films of vanadium dioxide (VO)2) Do not normally conduct electricity, their resistance increases up to 100,000 times when slightly heated. This can occur under the applied voltage, for example. That property is used to make high-speed switchable devices and sensors for direct current or alternating signals in terahertz, microwave, optical or infrared range.

Material scientists found V.O.2 Films became conductive in the mid-20th century. Until now, the exact mechanism behind the change in the electrical properties of the material was unknown. Be aware of that mechanism enables application-oriented content design. This involves the synthesis of thin films with predetermined properties, such as the temperature at which the conductivity changes or the ratio between resistances before and after heating.

“Among the most useful things, these films can be valuable for sensors for precious bolometers. Boliometer thermal imaging systems.2 The study, co-authored and MIPT doctoral student Viktor Polozov at the University’s Landau School of Physics and Research, commented, “can increase their sensitivity and response rate, while increasing their applicability to fast-moving objects.” ”

MIPT researchers proposed a scenario for V.O.2 Film transition between insulating and conductive state. The film is first heated and the conductive fields are sporadically exposed. Then the regions are added, which turn into a channel that makes the operation of the film operational. Further widens the heating channel, reducing the film’s resistance.

This process occurs through a so-called blow-up regime. Similar observations have already been made in other materials. For example, this regime is also characteristic for superconducting transitions in high-temperature superconductors.

To prove that V.O.2 The films go through a similar process, with Russian researchers relying on a combination of theory and experiment. On the one hand, they used available models that describe the processes occurring in the blow-up regime to estimate the current-voltage characteristics of the films and how the resistance should vary with temperature. On the other hand, the team synthesized their films with different properties and experimentally measured their parameters.

“Theoretical calculations agreed with the experimental findings, and which was true of films of different structures deposited on different substrates. This led us to conclude that the mechanism involved is universal — that is, it explains thermally induced conductivity in all thin VO. Does.2 Films, ”said Alexander Rakhmanov, professor at the Landau School of Physics and Research at MIPT, who co-authored the study.

Researchers confirm their hypothesis about infection in V.O.2 Blow-up is a characteristic of governance. Now that they know that this mechanism undergoes infection, the team can model that process. It is the focus of their future research.

Lighting the way for porous electronics and sensors

more information:
VI Polozov et al. Blow-up overheating instability in vanadium dioxide thin films, Physical Review B (2020). DOI: 10.1103 / PhysRevB.101.214310

Provided by Moscow Institute of Physics and Technology

Quotes: Scientists unravel the mystery of the material for promising infrared cameras (2020, 31 August) from on 1 September 2020 get

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