物理的気相蒸着法におけるプラズマ特性と膜物性に関する研究

第1章 序論 第2章 プラズマ診断方法 第3章 Al-Ar混合気体放電のプラズマパラメータと電離機構 第4章 RFマグネトロンスパッタリングのプラズマ診断 第5章 RFマグネトロンスパッタリングによるTiO_2薄膜の性質とプラズマ特性の相関 第6章 プラズマの能動的制御によるTiO_2膜質の制御 第7章 総括Made available in DSpace on 2012-09-06T02:19:38Z (GMT). No. of bitstreams: 2 okimura1.pdf: 9115346 bytes, checksum: 08a718516abc75ff8d22ddc4d2d873b7 (MD5) okimura2.pdf: 13331367 bytes, checksum: 52aa11788cd8b41e32bf7c7daf536d85 (MD5) Previous issue date: 1995-07-2

Dynamic inversion of planar-chiral response of terahertz metasurface based on critical transition of checkerboard structures

Dynamic inversion of the planar-chiral responses of a metasurface is experimentally demonstrated in the terahertz regime. To realize this inversion, the critical transition of the checkerboard-like metallic structures is used. Resonant structures with planar chirality and their complementary enantiomeric patterns are embedded in the checkerboard. Using vanadium dioxide as a variable resistance, the metasurface is implemented in the terahertz regime. The responses of the metasurface to circularly polarized waves are then characterized by terahertz time-domain spectroscopy. Further, the sign of the circular conversion dichroism, which is closely related to the handedness of the planar chirality of the metasurface, is observed to be inverted at 0.64 THz by varying the temperature. Such invertible planar-chiral responses can be applied practically to the handedness-invertible chiral mirrors

Persistent M2 phase in strongly strained (011)-oriented grains in VO2 films grown on sapphire (001) in reactive sputtering

This work was supported by a Grant-in-Aid for Scientific Research (Grant No. 15K04652) from the Japan Society for the Promotion of Science.We report on the first observation of the persistent M2 phase in strongly strained (011)-oriented grains in VO₂ films grown on Al₂O₃ (001) substrates by means of conventional rf reactive sputtering under adequate deposition conditions. Spatially resolved micro-Raman spectra clearly showed that (011)-oriented large crystalline grains with the cR-axis parallel to the substrate resulted in the appearance of the M2 phase over a wide temperature range of 30 °C. A close correlation of the appearance range of the M2 phase with the in-plane tensile stress of (011)-oriented grains was revealed by X-ray diffraction. We present a phase diagram for the M1, M2, and R phases in relation to the stress of (011)-oriented grains and temperature. It was shown that (011)-oriented micrometer-sized long grains play a crucial role in the emerging structural phase transition (SPT) via an M2 phase even in a film grown on Al₂O₃ (001), which is ordinarily reserved for the (020)-oriented VO₂ growth. The results shown here will contribute to make clear the conditions for obtaining VO₂ films with the appearance of the M2 phase in their SPT process

Photo-induced lattice softening of excited-state VO2

In this letter, we demonstrated the photoexcitation of metallic phase vanadium dioxide (VO_2) with time-resolved x-ray diffraction measurements. Through the photoexcitation, the metallic phase VO_2 transitioned to the similar transient state, which was presented in the insulator to metal phase transition in the time-scale of ∼10 ps. This transient state was accessed only by the photoexcitation and not through further thermal excitation. The presence of the transient state could be an important factor in any further application of the phase transition phenomena

Characterization of structural dynamics of VO2 thin film on c-Al2O3 using in-air time-resolved x-ray diffraction

The lattice motion and displacement of atoms in the unit cell in vanadium dioxide (VO2) grown on c-Al2O3 were characterized by static and time-resolved x-ray diffraction (XRD) measurements. The monoclinic-tetragonal phase transition of the VO2 unit cell and the twist motion of vanadium atoms in the unit cell were observed. The time-resolved XRD measurements were performed in air using a tabletop high-repetition femtosecond laser. The results obtained from the time-resolved XRD measurements suggested that the unit cell of the low-temperature monoclinic VO2 transformed into the high-temperature tetragonal phase extremely rapidly (within 25 ps); however, the atoms in the unit cell fluctuated or vibrated about the center of the tetragonal coordinates, which abated within ∼100 ps. Thus, the time-resolved XRD measurements of the Bragg angle, intensity, and width of the diffraction lines simultaneously revealed the phase transition of VO2 and the atomic motion in the unit cell

Stress-induced VO2 films with M2 Monoclinic Phase Stable at Room Temperature Grown by Inductively Coupled Plasma-Assisted Reactive Sputtering

International audience[No abstract