部分Si取代单壁碳纳米管的带隙统一
Band gap unification of partially Si-substituted single wall carbon nanotubes
摘要：
用LDA平面波能带结构计算方法研究了一组原始单壁SiC纳米管、Si取代的碳纳米管和SiC片的原子和电子结构。碳原子被Si连续取代导致金属（8，8）SWCNT的能谱中的带隙开口，其中带隙对Si浓度具有近似二次依赖性。对于半导体（10，0）SWCNT的相同取代导致在约25%的Si浓度下的带隙最小值（0.27eV）。在12- 18%的Si浓度区域中，两种类型的纳米管在γ-γ点处具有小于0.5eV的直接带隙。对手性（8，2）SWSi_（0.15）C_（0.85）NT系统的计算给出了类似的（0.6 eV）直接带隙。与随机分布相比，Si原子在原子晶格中的规则分布在能量上优选约0.1 eV/原子。与时间相关的DFT计算表明，硅取代充分增加（大约由一个数量级）的总概率的光学跃迁在近红外区域，这是由于在金属单壁碳纳米管的直接带隙的开放，统一的性质和能量的带隙的所有单壁碳纳米管物种，大的<Si3p |r| Si3s>径向积分值和参与的Si 3d状态的化学键在价带和电导带。
英文摘要：
The atomic and electronic structure of a set of pristine single wall SiC nanotubes as well as Si-substituted carbon nanotubes and a SiC sheet was studied by the LDA plane wave band structure calculations. Consecutive substitution of carbon atoms by Si leads to a gap opening in the energetic spectrum of the metallic (8,8) SWCNT with approximately quadratic dependence of the band gap upon the Si concentration. The same substitution for the semiconductor (10,0) SWCNT results in a band gap minimum (0.27 eV) at ~25% of Si concentration. In the Si concentration region of 12-18%, both types of nanotubes have less than 0.5 eV direct band gaps at the Gamma-Gamma point. The calculation of the chiral (8,2) SWSi_0.15C_0.85NT system gives a similar (0.6 eV) direct band gap. The regular distribution of Si atoms in the atomic lattice is by ~0.1 eV/atom energetically preferable in comparison with a random distribution. Time dependent DFT calculations showed that the silicon substitution sufficiently increases (roughly by one order of magnitude) the total probability of optical transitions in the near infrared region, which is caused by the opening of the direct band gap in metallic SWCNTs, the unification of the nature and energy of band gaps of all SWCNT species, the large values of <Si3p|r|Si3s> radial integrals and participation of Si3d states in chemical bonding in both valence and conductance bands.
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