Yan Binghai, Park Changwon, Ihm Jisoon, Zhou Gang, Duan Wenhui, Park Noejung
Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Korea.
J Am Chem Soc. 2008 Dec 17;130(50):17012-5. doi: 10.1021/ja805557g.
We investigate the electronic structures and electron emission properties of alkali-doped boron-nitride nanotubes (BNNTs) using density-functional theory calculations. We find that the nearly free-electron (NFE) state of the BNNT couples with the alkali atom states, giving rise to metallic states near the Fermi level. Unlike the cases of potassium-doped carbon nanotubes, not only the s but the d orbital state substantially takes part in the hybridization, and the resulting metallic states preserve the free-electron-like energy dispersion. Through first-principles electron dynamic simulations under applied fields, it is shown that the alkali-doped BNNT can generate an emission current 2 orders of magnitude larger than the carbon nanotube. The nodeless wave function at the Fermi level, together with the lowered work function, constitutes the major advantage of the alkali-doped BNNT in electron emission. We propose that the alkali-doped BNNT should be an excellent electron emitter in terms of the large emission current as well as its chemical and mechanical stability.
我们使用密度泛函理论计算研究了碱掺杂氮化硼纳米管（BNNTs）的电子结构和电子发射特性。我们发现，BNNT的近自由电子（NFE）态与碱原子态耦合，在费米能级附近产生金属态。与钾掺杂碳纳米管的情况不同，不仅s轨道态而且d轨道态都大量参与杂化，并且所产生的金属态保留了类似自由电子的能量色散。通过在外加场下的第一性原理电子动力学模拟表明，碱掺杂的BNNT能够产生比碳纳米管大两个数量级的发射电流。费米能级处的无节点波函数，连同降低的功函数，构成了碱掺杂BNNT在电子发射方面的主要优势。我们提出，就大发射电流以及其化学和机械稳定性而言，碱掺杂的BNNT应该是一种优异的电子发射体。
