Tuning energy barriers by doping 2D group-IV monochalcogenides
Tuning energy barriers by doping 2D group-IV monochalcogenides
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DOI：
10.1063/5.0008502
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发表时间：
2020-05
影响因子：
3.2
通讯作者：
A. Du;Zachary Pendergrast;S. Barraza‐Lopez
中科院分区：
文献类型：
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作者：
A. Du;Zachary Pendergrast;S. Barraza‐Lopez
结构简并支持新一代二维材料的铁性行为，并导致在外场、电荷掺杂和/或温度下发生特殊的二维结构相变。最直接的指标是弹性能垒，它定义为(简并的)结构基态单胞与结构对称性增强的单胞之间的能量差。二维材料与块体衬底的接近程度可以影响发生这些转变的临界场和/或温度的大小，第一个影响是相对电荷转移，这可能会触发结构量子相变。考虑到这一物理图景，我们报道了适度电荷掺杂(每单位晶胞的电子数在-0.2美元和+0.2美元范围内)对铁弹性黑色磷烯和九个铁电单硫化物单层的弹性能垒的影响。弹性能垒J_S是产生从Pnm2_1到P4/Nmm的二维结构转变所需的能量。与铁弹性SnO单分子膜对弹性能垒的影响类似，在相同掺杂量下，第IV族化合物单层显示出可调的弹性能垒：在适度的空穴(电子)掺杂不超过十分之一电子或每个原子一个空穴的情况下，可以设计减少(增加)$J_S。
Structural degeneracies underpin the ferroic behavior of next-generation two-dimensional materials, and lead to peculiar two-dimensional structural transformations under external fields, charge doping and/or temperature. The most direct indicator of the ease of these transformations is an {\em elastic energy barrier}, defined as the energy difference between the (degenerate) structural ground state unit cell, and a unit cell with an increased structural symmetry. Proximity of a two-dimensional material to a bulk substrate can affect the magnitude of the critical fields and/or temperature at which these transformations occur, with the first effect being a relative charge transfer, which could trigger a structural quantum phase transition. With this physical picture in mind, we report the effect of modest charge doping (within $-0.2$ and $+0.2$ electrons per unit cell) on the elastic energy barrier of ferroelastic black phosphorene and nine ferroelectric monochalcogenide monolayers. The elastic energy barrier $J_s$ is the energy needed to create a $Pnm2_1\to P4/nmm$ two-dimensional structural transformation. Similar to the effect on the elastic energy barrier of ferroelastic SnO monolayers, group-IV monochalcogenide monolayers show a tunable elastic energy barrier for similar amounts of doping: a decrease (increase) of $J_s$ can be engineered under a modest hole (electron) doping of no more than one tenth of an electron or a hole per atom.