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利用密度泛函理论(DFT)和非平衡格林函数(NEGF)的方法研究了S空位缺陷对(8,8)MoS_2纳米管输运性质的影响。构建了10种缺陷结构,主要考察了S空位缺陷的不同位置和缺陷量对输运性质的影响。研究结果表明,相对于纳米管的外层S原子,S缺陷更倾向于定位在纳米管的内层。不同位置的硫缺陷对能带结构的影响明显不同,外层硫缺陷既可以引入供体带也可以引入受体带,而内层硫缺陷只提供受体带。S缺陷的引入有双重作用:一是由于降低带隙对导电起促进作用;二是由于引入陷阱效应对导电起抑制作用。计算结果表明MoS_2纳米管引入S缺陷后,导电性均增强。值得注意的是引入较多的外层硫缺陷会更加利于增强导电性,原因可能是更多的注入了载流子。
The effects of S vacancies on the transport properties of (8,8) MoS 2 nanotubes were studied by means of density functional theory (DFT) and non-equilibrium Green’s function (NEGF). Ten kinds of defect structures were constructed, mainly investigating the influence of different locations and defects on the transport properties of S vacancy defects. The results show that, compared with the outer S atoms of nanotubes, S defects are more likely to be located in the inner layer of nanotubes. Sulfur defects at different locations have markedly different effects on the band structure. Outer sulfur defects can be introduced into the donor and acceptor bands, while the inner sulfur defects provide only acceptor bands. The introduction of S defects has a dual role: one is to reduce the band gap on the conductivity play a catalytic role; the second is due to the introduction of the trap effect on the conductivity from the inhibition. The calculated results show that the conductivity of MoS_2 nanotubes increases after introducing S defects. It is noteworthy that the introduction of more outer sulfur defects will be more conducive to enhancing the conductivity, the reason may be more injected into the carrier.