Synthesis and First-Principles Studies of Single-Crystalline β-BC2N with Oxygen-Bearing Defects

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• 作者：Li Hou ; Faming Gao ; Huiyang Gou ; Zhibing Wang ; Min Tian
• 刊名：Crystal Growth & Design
• 出版年：2008
• 出版时间：June 2008
• 年：2008
• 卷：8
• 期：6
• 页码：1972 - 1976
• 全文大小：1970K
• 年卷期：v.8,no.6(June 2008)
• ISSN：1528-7505

文摘

Single-crystalline B-C-N nanorods were prepared at 500 °C and less than about 20 MPa. Results from X-ray powder diffraction (XRD) and selected-area electron diffraction (SAED) measurements suggest that the synthesized single-crystalline B-C-N is of tetragonal structure and its lattice constants are a = 7.12(5) Å and c = 3.57(3) Å. The nanorods all are very straight, and the ratios of length to diameter are between 5 and 30. High resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) observations confirm the well-defined nanorods grown preferentially perpendicular to the [220] direction develop tetragonal morphologies. The energy-loss spectroscopy (EELS) and energy-dispersive X-ray (EDX) elemental mapping confirm that the nanorod is composed of B, C, N, and a trace of oxygen, and its stoichiometry is determined to be close to BC₂N. First-principles calculations confirm that the as-prepared sample is superlattice phase of β-BC₂N phase with defects of the C_N′ and the O_N′. In addition, it is a semiconductor material with a direct energy band gap 1.21 eV. The calculated hardness is comparable to that of diamond.