Silicon carbides are basilic ceramics with proper bandgaps (2.4–3.3 eV) and unique optical properties. SiC@C monocrystal nanocapsules with different morphologies, sizes, and crystal types were synthesized via the fast and facile direct current (DC) arc discharge plasma method. The influence of Ar atmosphere on the formation of nanocrystal SiC polytypes was investigated by optical emission spectroscopy (OES) diagnoses on the arc discharge plasma. Boltzmann’s plot was used to estimate the temperatures of plasma containing different Ar concentrations as 10,582 K (in 2 × 10⁴ Pa of Ar partial pressure) and 14,523 K (in 4 × 10⁴ Pa of Ar partial pressure). It was found that higher energy state of plasma favors the ionization of carbon atoms and promotes the formation of α-SiC, while β-SiC is generally coexistent. Heat-treatment in air was applied to remove the carbon species in as-prepared SiC nanopowders. Thus, the intrinsic characters of SiC polytypes reappeared in the ultraviolet–visible (UV–vis) light absorbance. It was experimentally revealed that the direct bandgap of SiC is 5.72 eV, the indirect bandgap of β-SiC (3C) is 3.13 eV, and the indirect bandgap of α-SiC (6H) is 3.32 eV; visible quantum confinement effect is predicted for these polytypic SiC nanocrystals.

中文翻译：

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直流电弧放电等离子体在多晶型SiC合成中的高能Ar离子的光谱发射光谱诊断

碳化硅是具有适当的带隙（2.4–3.3 eV）和独特的光学性能的硅酸盐陶瓷。通过快速，简便的直流电弧放电等离子体方法合成了具有不同形态，尺寸和晶体类型的SiC @ C单晶纳米胶囊。通过对电弧放电等离子体的光发射光谱法（OES）诊断，研究了氩气气氛对纳米晶SiC多晶型形成的影响。玻尔兹曼图被用来估计包含不同Ar浓度的等离子体的温度，分别为10,582 K（在2×10 ⁴ Pa的Ar分压下）和14,523 K（在4×10 ^4内）。Pa（Ar分压）。发现等离子体的更高能量状态有利于碳原子的电离并促进α-SiC的形成，而β-SiC通常共存。在空气中进行热处理以除去所制备的SiC纳米粉中的碳物质。因此，SiC多晶型的内在特征再次出现在紫外可见（UV-vis）吸光度中。实验表明，SiC的直接带隙为5.72 eV，β-SiC（3C）的间接带隙为3.13 eV，α-SiC（6H）的间接带隙为3.32 eV。这些多型SiC纳米晶体的可见量子限制效应被预测。