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Vanadium oxide films and fibers have been fabricated by the acetylacetonate sol-gel method followed by annealing in wet nitrogen. The samples are characterized by X-ray diffraction and electrical conductivity measurements. The effects of a sol aging, the precursor decomposition and the gas atmosphere composition on the annealing process, structure and properties of the films are discussed. The two-stage temperature regime of annealing of amorphous films in wet nitrogen for formation of the well crystallized VO2 phase is chosen: 1) 25-550°C and 2) 550-600°C. The obtained films demonstrate the metal-insulator transition and electrical switching. Also, the effect of the polyvinylpyrrolidone additive concentration and electrospinning parameters on qualitative (absence of defects and gel drops) and quantitative (length and diameter) characteristics of vanadium oxide fibers is studied.

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Metal-insulator transitions and other electronic transitions) 72.80.Ga (Transition-metal compounds)Abstract. Effect of doping with H and W on the properties of V2O5 and VO2 derived from V2O5 gel has been studied. It is shown that the treatment of V2O5 in low-temperature RF hydrogen plasma for 1 to 10 min. leads to either hydration of vanadium pentoxide or its reduction (depending on the treatment conditions) to lower vanadium oxides. For some samples, which are subject to plasma treatment in the discharge active zone, a non-ordinary temperature dependence of resistance, with a maximum at T ~ 100 K, is observed. For W-doped VO2 films, it is shown that substitution of V 4+ with W 6+ results in a decrease of the temperature of metal-insulator transition.Also, it has been shown that the doping of the initial films with ~3 at.% of W reduces the statistical scatter in the threshold parameters of the switching devices with S-shaped I-V characteristics on the basis of V2O5 gel films.

Electrical switching and rectifying properties of the metal-VO2-Si structures, on both p-type and n-type silicon, with vanadium dioxide films obtained by an acetylacetonate sol-gel method, are studied. The switching effect is shown to be due to the semiconductor-to-metal phase transition (SMPT) in vanadium dioxide. The shift of the switching threshold voltage, accompanied by the memory effect, in forward bias of the p-Si-VO2 anisotype heterojunction is observed. To explain this effect, a model is proposed which suggests the existence of an additional series resistance associated with a channel at the VO2/Si interface, where a SiOх layer forms during the VO2 deposition process. This resistance is responsible for both threshold switching characteristics, and the memory effect, and the oxygen ion electromigration process is shown to underlie this effect. Potential applications of the observed phenomena, combining the effects of ReRAM and SMPT, in oxide electronics are discussed.

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The paper describes the effect of doping with hydrogen and tungsten by means of plasma-immersion ion implantation (PIII) on the properties of vanadium dioxide and hydrated vanadium pentoxide films. It is shown that the parameters of the metal-insulator phase transition in VO 2 thin films depend on the hydrogen implantation dose. Next, we explore the effect of PIII on composition, optical properties, and the internal electrochromic effect (IECE) in V 2 O 5 ⋅nH 2 O films. The variations in the composition and structure caused by the hydrogen insertion, as well as those caused by the electrochromic effect, are studied by nuclear magnetic resonance, thermogravimetry, Raman spectroscopy, and X-ray structural analysis. It is shown that the ion implantation-induced hydrogenation can substantially enhance the manifestation and performance of the IECE in V 2 O 5 xerogel films. Finally, the effect of PIII-assisted doping with W on the parameters of electrical switching in Au/V 2 O 5 ⋅nH 2 O/Au sandwich structures is examined. It is shown that implanting small tungsten doses improves the switching parameters after forming. When implanting large doses, switching is observed without electroforming, and if electroforming is applied, the switching effect, on the contrary, disappears.