2022-Sustainable Industrial Processing Summit
SIPS2022 Volume 1 Alario-Franco Intl. Symp Solid State Chemistry

Editors:F. Kongoli, F. Marquis, S. Kalogirou, B. Raveau, A. Tressaud, H. Kageyama, A. Varez, R. Martins.
Publisher:Flogen Star OUTREACH
Publication Year:2022
Pages:154 pages
ISBN:978-1-989820-34-6 (CD)
ISSN:2291-1227 (Metals and Materials Processing in a Clean Environment Series)
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    Development of High-Pressure Treatment Technique for Epitaxial Thin Films and Fabrication of α-PbO2-type TiO2 Epitaxial Thin Films

    Yuki Sasahara1; Koki Kanatani2; Hiroaki Asoma3; Cédric Tassel1; Kazunori Nishio3; Hiroshi Kageyama1; Ryota Shimizu3; Masaki Azuma2; Norimasa Nishiyama2; Taro Hitosugi4;
    1KYOTO UNIVERSITY, Kyoto, Japan; 2TOKYO INSTITUTE OF TECHNOLOGY, Yokohama, Japan; 3TOKYO INSTITUTE OF TECHNOLOGY, Tokyo, Japan; 4THE UNIVERSITY OF TOKYO, Tokyo, Japan;
    Type of Paper: Regular
    Id Paper: 441
    Topic: 52

    Abstract:

    Materials under ultrahigh pressure (HP) exhibit a variety of interesting properties.[1] However, some of the HP-phase materials that are thermodynamically stable under HP (> 10 GPa) transforms into amorphous or different crystalline phase during decompression. If this back-transformation can be suppressed, we can obtain some functional HP-phase materials to be utilized in the future. To obtain such HP-phase materials under ambient pressure, we focused on the epitaxial stabilization of metastable-phase materials and came up with the idea of applying HP to thin-film samples.[2]
    We first investigated an HP-phase, α-PbO2-type TiO2 (orthorhombic, a = 0.454 nm, b = 0.549 nm, c = 0.491 nm). This phase is obtainable under ambient pressure. Unfortunately, most of the reported data was about the product in the form of powder, and only a few reports about the fabrication of single crystals are currently available. In particular, single-phase epitaxial thin films have not been reported. In this study, we developed a technique for applying HP (8 GPa) to thin-film samples. Using a rutile TiO2(100) epitaxial thin film as a precursor, we fabricated epitaxial thin films of single-phase α-PbO2-type TiO2(100) by inducing a structural phase transition at ultrahigh pressure.
    Thin films of epitaxial rutile TiO2(100) (thickness: ~100 nm) were deposited as precursors on Al2O3(001) (5 mm in diameter and 0.5 mm in height) using pulsed laser deposition. HP treatment for thin films was performed using a Kawai-type multi-anvil HP apparatus. The precursor thin film was heated up to 1000 °C under HP of 8 GPa, and then kept for 0.5 h. After the heating step, the film was quenched to room temperature (RT), followed by decompression.
    The results of X-ray diffraction and Raman spectroscopy indicate that a single-phase α-PbO2-type TiO2(100) epitaxial thin film has been obtained. It should be stressed here that rocking-curve full width at half maximum of the 200 peak showed a quite small value of 0.11°, indicating very high crystallinity. Our present study indicates that HP treatment to thin-film samples allows us to fabricate high-quality HP-phase epitaxial thin films.

    Keywords:

    Advances in the synthesis routes; High pressure synthesis, Epitaxial thin film

    References:

    [1] Snider et al., Nature, 586, 373 (2020).
    [2] Sasahara et al., AIP Adv., 10, 025125 (2020).

    Cite this article as:

    Sasahara Y, Kanatani K, Asoma H, Tassel C, Nishio K, Kageyama H, Shimizu R, Azuma M, Nishiyama N, Hitosugi T. (2022). Development of High-Pressure Treatment Technique for Epitaxial Thin Films and Fabrication of α-PbO2-type TiO2 Epitaxial Thin Films. In F. Kongoli, F. Marquis, S. Kalogirou, B. Raveau, A. Tressaud, H. Kageyama, A. Varez, R. Martins. (Eds.), Sustainable Industrial Processing Summit SIPS2022 Volume 1 Alario-Franco Intl. Symp Solid State Chemistry (pp. 113-114). Montreal, Canada: FLOGEN Star Outreach