Hexagonal AlN: Dimensional-crossover-driven band-gap transition
Hexagonal AlN: Dimensional-crossover-driven band-gap transition
复制标题
DOI：
10.1103/physrevb.91.085430
复制
发表时间：
2015-02-27
影响因子：
3.7
通讯作者：
Peeters, F. M.
中科院分区：
文献类型：
--
作者：
Bacaksiz, C.;Sahin, H.;Peeters, F. M.
受最近一项报道成功合成六方 (h) AlN 实验的启发 [Tsipas 等人，Appl.物理。莱特。 103, 251605 (2013)]，我们通过第一性原理计算研究了 h-AlN 的块体、双层和单层结构的结构、电子和振动特性。我们证明了块状 h-AlN 的六方相是一种稳定的直接带隙半导体。计算的声子谱显示出274 cm(-1)处的刚性层剪切模式和703 cm(-1)处的E-g模式，这可以通过拉曼测量观察到。此外，单层h-AlN是一种非磁性基态的间接带隙半导体。对于双层结构，AA'型堆积是最有利的，并且层间相互作用强。虽然 N 层 h-AlN 是 N = 1 - 9 的间接带隙半导体，但我们预测较厚的结构 (N >= 10) 在伽马点具有直接带隙。 h-AlN 中与层数相关的带隙跃迁很有趣，因为它与过渡金属二硫属化物中获得的间接到直接交叉显着不同。
Motivated by a recent experiment that reported the successful synthesis of hexagonal (h) AlN [Tsipas et al., Appl. Phys. Lett. 103, 251605 (2013)], we investigate structural, electronic, and vibrational properties of bulk, bilayer, and monolayer structures of h-AlN by using first-principles calculations. We show that the hexagonal phase of the bulk h-AlN is a stable direct-band-gap semiconductor. The calculated phonon spectrum displays a rigid-layer shear mode at 274 cm(-1) and an E-g mode at 703 cm(-1), which are observable by Raman measurements. In addition, single-layer h-AlN is an indirect-band-gap semiconductor with a nonmagnetic ground state. For the bilayer structure, AA'-type stacking is found to be the most favorable one, and interlayer interaction is strong. While N-layered h-AlN is an indirect-band-gap semiconductor for N = 1 - 9, we predict that thicker structures (N >= 10) have a direct band gap at the Gamma point. The number-of-layer-dependent band-gap transitions in h-AlN is interesting in that it is significantly different from the indirect-to-direct crossover obtained in the transition-metal dichalcogenides.