Identification and roles of nonstoichiometric oxygen in amorphous Ta2O5 thin films deposited by electron beam and sputtering processes

Cedric Mannequin, Tohru Tsuruoka, Tsuyoshi Hasegawa, Masakazu Aono

    Research output: Contribution to journalArticle

    9 Citations (Scopus)

    Abstract

    The morphology and composition of tantalum oxide (Ta2O5) thin films prepared by electron-beam (EB) evaporation and radio-frequency sputtering (SP) were investigated by grazing incidence X-ray diffraction (GIXRD), X-ray reflectometry (XRR), atomic force microscopy, Fourier transformed infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). GIXRD revealed an amorphous nature for both films, and XRR showed that the density of the Ta2O5-EB films was lower than that of the Ta2O5-SP films; both films have lower density than the bulk value. A larger amount of molecular water and peroxo species were detected for the Ta2O5-EB films by FTIR performed in ambient atmosphere. XPS analyses performed in vacuum confirmed the presence of hydroxyl groups, but no trace of chemisorbed molecular water was detected. In addition, a higher oxygen nonstoichiometry (higher O/Ta ratio) was found for the EB films. From these results, we conclude that the oxygen nonstoichiometry of the EB film accounted for its lower density and higher amount of absorbed molecular water. The results also suggest the importance of understanding the dependence of the structural and chemical properties of thin amorphous oxide films on the deposition process.

    Original languageEnglish
    Pages (from-to)426-435
    Number of pages10
    JournalApplied Surface Science
    Volume385
    DOIs
    Publication statusPublished - 2016 Nov 1

    Fingerprint

    Amorphous films
    Sputtering
    Electron beams
    Oxygen
    Thin films
    Oxide films
    Water
    Infrared spectroscopy
    X ray photoelectron spectroscopy
    Tantalum oxides
    X ray diffraction
    X rays
    Hydroxyl Radical
    Chemical properties
    Structural properties
    Atomic force microscopy
    Evaporation
    Vacuum
    Chemical analysis

    Keywords

    • Composition
    • Fourier transformed infrared spectroscopy
    • HO absorption
    • Nonstoichiometric oxygen
    • Oxides
    • X-ray photoelectron spectroscopy

    ASJC Scopus subject areas

    • Surfaces, Coatings and Films

    Cite this

    Identification and roles of nonstoichiometric oxygen in amorphous Ta2O5 thin films deposited by electron beam and sputtering processes. / Mannequin, Cedric; Tsuruoka, Tohru; Hasegawa, Tsuyoshi; Aono, Masakazu.

    In: Applied Surface Science, Vol. 385, 01.11.2016, p. 426-435.

    Research output: Contribution to journalArticle

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    AU - Aono, Masakazu

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    AB - The morphology and composition of tantalum oxide (Ta2O5) thin films prepared by electron-beam (EB) evaporation and radio-frequency sputtering (SP) were investigated by grazing incidence X-ray diffraction (GIXRD), X-ray reflectometry (XRR), atomic force microscopy, Fourier transformed infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). GIXRD revealed an amorphous nature for both films, and XRR showed that the density of the Ta2O5-EB films was lower than that of the Ta2O5-SP films; both films have lower density than the bulk value. A larger amount of molecular water and peroxo species were detected for the Ta2O5-EB films by FTIR performed in ambient atmosphere. XPS analyses performed in vacuum confirmed the presence of hydroxyl groups, but no trace of chemisorbed molecular water was detected. In addition, a higher oxygen nonstoichiometry (higher O/Ta ratio) was found for the EB films. From these results, we conclude that the oxygen nonstoichiometry of the EB film accounted for its lower density and higher amount of absorbed molecular water. The results also suggest the importance of understanding the dependence of the structural and chemical properties of thin amorphous oxide films on the deposition process.

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