Deep Ultraviolet Light-Emitting Hexagonal Boron Nitride Synthesized at Atmospheric Pressure
Yoichi Kubota*,
Kenji Watanabe,
Osamu Tsuda and
Takashi Taniguchi
National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan.
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Fig. 1. Optical micrographs of recrystallized hBN obtained with a Ni-Mo solvent. (A) Typical hBN crystal on the solidified solvent (as grown). (B) A fragment of aggregate hBN crystals after acid treatment (the inset is an optical micrograph of a recovered sample). The shiny white regions are reflected light.
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Fig. 2. Characteristics of recrystallized hBN grown in a Ni-Mo solvent at atmospheric pressure. (A) Raman spectrum obtained from recrystallized hBN. (B) X-ray diffraction profile of recrystallized hBN after being ground to fine powder. arb., arbitrary.
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Fig. 3. Cathodoluminescence spectra of recrystallized hBN at room temperature. (A) hBN obtained with a Ni solvent. (B) hBN obtained with a Ni-Mo solvent. (C) Direct quality comparison of the emission characteristics. Solid line, hBN obtained with a Ni-Mo solvent at atmospheric pressure (in this study); dotted line, hBN obtained with a Ba-BN solvent at high pressure and high temperature (HP-HT).
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Fig. 4. Images of hBN crystal grown on the a-plane sapphire substrate (obtained with a Ni-Mo solvent prepared at 1400°C). (A) Differential interference microscopic image. (B) Cathodoluminescence image for 215-nm band. We did not find any intensity change of the measured spectra between the grain boundary and the plane surface area when measuring the point-to-point mode of the cathodoluminescence system, where the electron beam remained stationary and the measured luminescence was confined to the exposed spot area.
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