Crystallography and structural evolution of LiNbO3 and LiNb1-xTaxO3 films on sapphire prepared by high-rate thermal plasma spray chemical vapor deposition

D. V. Shtansky, S. A. Kulinich, K. Terashima, T. Yoshida, Y. Ikuhara

    Research output: Contribution to journalArticle

    11 Citations (Scopus)

    Abstract

    The structure and the crystallography of lithium niobate and lithium niobate-tantalate thin films (0.2-1.0 μm in thickness) with the tantalum composition range of 0 ≤ x ≤ 0.5 grown on (0001) sapphire substrate by thermal plasma spray chemical vapor deposition have been studied by means of cross-sectional high-resolution transmission electron microscopy and x-ray diffraction. The tantalum composition in the films shows a minor effect on the rocking curve full width at half maximum values. The narrowest rocking curve width was obtained for the LiNb0.5Ta0.5O3 film to be as low as 0.25° λ. The films are under compressive strain along the c direction; c- and a-axis lattice parameters are correspondingly smaller and higher than those of the bulk single crystal. Under optimized growth conditions, the LiNbO3 and LiNb1-xTaxO3 films are 97% c-axis oriented. The film out-of-plane orientation changes from the [0001] to the [0112] direction by either decreasing the growth rate or increasing the substrate temperature. Particular attention has been paid to the orientation of individual grains in the partly c-axis-oriented films. The results demonstrate that their orientations are not random and specific orientation relationships are preferred for the film nucleation. The surface of as-received sapphire substrate reveals polishing defects with the well-defined surface ledges of 1-2 nm in height with smooth terraces of 25 nm in width. In the case of columnar growth, the terrace width becomes a limiting factor controlling the lateral crystallite size in the film. Finally, the film growth mechanism is discussed.

    Original languageEnglish
    Pages (from-to)2271-2279
    Number of pages9
    JournalJournal of Materials Research
    Volume16
    Issue number8
    DOIs
    Publication statusPublished - 2001 Aug

    ASJC Scopus subject areas

    • Materials Science(all)
    • Condensed Matter Physics
    • Mechanics of Materials
    • Mechanical Engineering

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