Benzene-like N6 rings in a Be2N6 monolayer: a stable 2D semiconductor with high carrier mobility
Benzene-like N6 rings in a Be2N6 monolayer: a stable 2D semiconductor with high carrier mobility
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DOI：
10.1039/c7tc03363j
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发表时间：
2017-11
影响因子：
6.4
通讯作者：
Feng Li;Yu Wang;Hong Wu;Zhifa Liu;U. Aeberhard;Yafei Li
中科院分区：
文献类型：
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作者：
Feng Li;Yu Wang;Hong Wu;Zhifa Liu;U. Aeberhard;Yafei Li
设计具有高载流子迁移率的新型二维 (2D) 半导体对于材料创新来说是非常理想的，特别是当配置具有新颖的拓扑特性时。在这里，我们提出了基于第一原理的二维晶体设计，即 Be2N6 单层。其中，每个N原子由两个相邻的N原子和一个Be原子共享，形成新的类苯N6环部分。与六嗪的不稳定性不同，Be2N6 单层具有适中的内聚能、良好的动学和热力学稳定性，这是由于 Be 元素形成 12 个经典的二中心双电子（2c–2e）σ 键和 5 个多中心 6c–2e π 键的稳定作用。一个晶胞中有10个π电子，满足Huckel规则[4n+2]（n=2），表明Be2N6单层芳香性。因此，Be2N6 单层具有高达 200 J m−2 的超高机械强度。粒子群优化 (PSO) 计算表明，含环 N6 的 Be2N6 单层是二维形式中能量最低的构型，化学计量比为 1:3，因此可以通过实验合成。此外，Be2N6 单层是一种间接半导体，在混合功能水平上的带隙为 1.71 eV，接近广泛用于太阳能电池的体非晶硅~1.6 eV。此时，Be2N6 单层观察到高达~104 cm2 V−1 s−1 的高电子迁移率和~105 cm−1 的可见光吸收。如果实现，它不仅将丰富对氮键合性质的了解，而且还可能在电子和光电子领域具有潜在的应用。
Designing new two-dimensional (2D) semiconductors with high carrier mobilities is highly desirable for material innovation, especially when the configuration has novel topological properties. Here, we proposed a first-principles-based design of a 2D crystal, namely a Be2N6 monolayer. In which, each N atom is shared by two neighboring N atoms and one Be atom, forming a novel moiety of benzene-like N6 rings. Rather than the instability of hexazine, the Be2N6 monolayer has a moderate cohesive energy, good kinetic and thermodynamic stability, due to the stabilization effect of the Be element by forming twelve classical two-centre–two-electron (2c–2e) σ-bonds and five multicenter 6c–2e π-bonds. There are ten π electrons in a unit cell, which satisfies the Huckel rule [4n + 2] (n = 2), indicating the Be2N6 monolayer aromaticity. As a result, the Be2N6 monolayer has an ultra-high mechanical strength of up to 200 J m−2. Particle-swarm optimization (PSO) computations reveal that a cyclo-N6-containing Be2N6 monolayer is the lowest-energy configuration in 2D forms with a stoichiometry of 1 : 3, and therefore could be synthesized experimentally. Furthermore, the Be2N6 monolayer is an indirect semiconductor with a band gap of 1.71 eV at the hybrid functional level, close to that of the bulk amorphous silicon ∼1.6 eV widely used in solar cells. At this point, the high electron mobility of up to ∼104 cm2 V−1 s−1 and visible-light absorption of ∼105 cm−1 are observed for the Be2N6 monolayer. If realized, it will not only enrich the knowledge of the bonding nature of nitrogen but could also have potential applications in electronics and optoelectronics.