Work

Reduction Processes in Thin-Film Vanadium Oxides for Application in Optoelectronic Devices

Year: 2026

Type: article

Abstract: The paper describes the production of thin-film vanadium oxide coatings on plane-parallel substrates of silica glass, sapphire, and silicon, as well as optical fibers. These coatings are synthesized by chemical deposition from a gas phase using a precursor, triisopropoxyvanadium (V) oxide. During the process, the optical properties of the deposited material are monitored in real-time. The possibility of modifying the composition of VOx by subsequent annealing in hydrogen, oxygen, or argon is demonstrated. This allows for optimizing the characteristics of semiconductor-metal phase transitions. The composition and properties of these samples are studied using optical, terahertz, and Raman spectroscopy, as well as temperature-dependent analysis of electrical resistance. Changes in the morphology of the coated surface as a result of heat treatment are observed. The relationship between annealing conditions and the optical constants of deposited thin film materials was estimated for the first time using the effect of a lossy mode resonance. This method made it possible to accurately determine the threshold conversion temperature of the stoichiometric composition of oxide with high precision. Optimal synthesis conditions were determined for obtaining vanadium dioxide (VO2) and pentoxide (V2O5). The reduction of VOx to VO2 in hydrogen and argon atmospheres during post-combustion annealing was studied in detail and its effectiveness was compared. For the first time, it was shown that the reduction of higher vanadium oxides occurs due to the presence of elemental carbon in the material volume, which is formed from an organometallic precursor during the growth of vanadium oxide. VO2 coatings obtained by annealing in hydrogen have a smaller hysteresis loop width (~5 ℃) during the phase transition, unlike similar coatings formed by annealing with argon (~9 ℃). However, they contain a significant number of OH groups in their composition. At the same time, both types of coatings demonstrate a jump in transmission at 1 THz and a 50-60% increase in electrical resistance, which is accompanied by a factor of 10³-10⁴ change in resistance.

Source: Nanomaterials

DOI: 10.3390/nano16090528

Authors: Dmitriy P. Sudas, Vasiliy O. Yapaskurt, V. A. Luzanov, Galina Yakuscsheva, K. A. Kuznetsov, P. I. Kuznetsov

Institution: Lomonosov Moscow State University

Language: English

Topic: Transition Metal Oxide Nanomaterials

Subfield: Polymers and Plastics

Field: Materials Science

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,896

Funder: Russian Science Foundation