Institute for Physics

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Author: search.filters.author.Jovanovski, StefanLanguage: search.filters.language.English

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    Structural and optical properties of mixed phase WO3 – ZnWO4 films synthesized from thermally oxidized metallic Zn–W films
    (Elsevier BV, 2026-06)
    Jovanovski, Stefan
    ;
    Popović, Maja
    ;
    Novaković, Mirjana
    ;
    Tungsten-bearing compounds have attracted significant interest in recent years, especially in thin films or nano powder form, due to their photocatalytic activity stemming from their wide band gap semiconductor properties. This study presents the synthesis of mixed phase WO3–ZnWO4 films synthesized by thermal oxidation of co-sputtered metallic Zn–W films. From XRD analysis it appeared that annealing at 600 °C leads to the formation of the monoclinic Zn-tungstate phase within the WO3 matrix with crystallite size about 50 nm for both phases. The XPS analysis of the O1s peak showed mixed phase compound of WO3 matrix with about 13 at.% of ZnWO4. Raman and infrared spectroscopy further characterize the structural features, revealing the WO6 octahedral unit as main building block in the structure. The optical band gap of the annealed film was found to be 3.34 eV, indicating a wide gap semiconductor. The films displayed a UV induced Photoluminescence with broad PL spectra with emission maximum at about 2.48 eV. The study demonstrates that co-sputtering and annealing at 600 °C approach is effective for synthesizing of tungstate phase ZnWO4 within WO3 matrix.
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    Formation of WO3 thin films from RF sputtered tungsten films by air annealing: A cost-effective approach
    (National Library of Serbia, 2025)
    Jovanovski, Stefan
    ;
    Popovic, Maja
    ;
    Novakovic, Mirjana
    ;
    Rajic, Vladimir
    ;
    WO3 thin films were prepared by RF sputtering metallic tungsten onto glass substrates, followed by thermal oxidation through annealing in air. This technique is straightforward, cost-efficient, and time-effective, achieving high deposition rates of 16 nm/min on average at 200 W magnetron power for the highly homogeneous W-metallic films. SEM/EDX analysis showed that after annealing at 450ᵒC in air, the RF sputtered 269 nm thick metallic W films with a round grain morphology (~30 nm) turned into 420 nm thick nearly stoichiometric transparent WO3 (tungsten (VI) oxide) film, with a dramatically changed morphology of aggregated crystal rods approximately 1 μm long. XRD and Raman spectroscopy confirmed a biphasic crystal structure, with a dominant monoclinic phase and a minor tetragonal phase. XPS analysis revealed the characteristic W4f7/2 and W4f5/2 electron peaks associated with the W6+ oxidation state, with no evidence of W5+ species, indicating a stoichiometric nature of the WO3 films.