[论文解读] Prediction of group IV-V hexagonal binary monolayers: electronic, optical, thermoelectric, and photocatalysis properties

Mohammad Ali Mohebpour, Shobair Mohammadi Mozvashi+2 more|arXiv (Cornell University)|Mar 21, 2020

2D Materials and Applications被引用 3

一句话总结

本研究通过从头算计算预测了八种稳定的氢化IV-V族二元单层材料（Si₂Y 和 Ge₂Y，Y = P, As, Sb, Bi），揭示其具有宽能带隙、可调的电子性质、强可见光吸收、线性二向色性、高载流子迁移率以及适合光催化应用的合适能带边。其主要贡献在于识别出具有前景的二维材料，适用于光电子学、热电材料以及太阳能燃料生成。

ABSTRACT

Group IV and V monolayers are very crucial 2D materials for their high carrier mobilities, tunable band gaps, and optical linear dichroism. Very recently, a novel group IV-V binary compound, Sn2Bi, has been synthesized on silicon substrate, and has shown very interesting electronic and thermoelectric properties. Further investigations show that show that the monolayer would be stable in freestanding form by hydrogenation. Inspired by this, by means of ab-initio calculations, we systematically predict and investigate eight counterparts of Sn2Bi, namely Si2P, Si2As, Si2Sb, Si2Bi, Ge2P, Ge2As, Ge2Sb, and Ge2Bi. The cohesive energies, phonon dispersions, and AIMD calculations show that, similar to Sn2Bi, all of these freestanding monolayers are stable when they are hydrogenated. These hydrogenated monolayers are semiconductors with wide band gaps, which are favorable for opto-electronic purposes. The Si2Y and Ge2Y structures possess indirect and direct band gaps, respectively. They represent very interesting optical characteristics, such as good absorption in the visible region and linear dichroism, which are crucial for solar cell and beam-splitting devices, respectively. Moreover, the Ge2P and Si2Sb monolayers are promising for highspeed nano-electronic devices, because of their high carrier mobility, whereas Si2Bi, Ge2P, and Si2As monolayers are suitable candidates for thermoelectricity. Finally, the Si2Sb and Si2Bi monolayers have suitable band gaps and band edge positions for photocatalytic water splitting. Summarily, our investigations offer very interesting and promising properties for this family of binary compounds. We hope that our predictions open ways to new experimental studies and fabrication of suitable 2D materials for next generation opto-electronic, thermoelectric, and photocatalytic devices.

研究动机与目标

• 识别在近期合成的Sn₂Bi之外的稳定、自由悬挂的IV-V族二元单层材料。
• 研究八种预测的单层化合物（Si₂P, Si₂As等）的结构、电子、光学和热电性质。
• 评估其在光电子学、热电学和光催化应用中的潜力。
• 确定氢化在稳定这些单层材料于自由悬挂形态中的作用。
• 为新型二维材料的实验合成提供全面的材料设计路线图。

提出的方法

• 采用包含范德华校正的密度泛函理论（DFT）进行精确的结构与能量分析。
• 计算结合能以评估预测单层材料的热力学稳定性。
• 进行声子色散计算以确认动力学稳定性。
• 开展从头算分子动力学（AIMD）模拟，验证室温下的热稳定性。
• 分析电子能带结构，确定直接/间接带隙及载流子有效质量。
• 评估光学性质，包括吸收光谱和可见光范围内的线性二向色性。

实验结果

研究问题

• RQ1 氢化后，哪些IV-V族二元单层材料在自由悬挂形态下具有热力学和动力学稳定性？
• RQ2 这些单层材料的电子能带结构和有效质量如何？它们如何影响载流子迁移率？
• RQ3 不同组分的光学性质（如可见光吸收和线性二向色性）有何差异？
• RQ4 哪些单层材料具有适合光催化分解水的合适能带边位置？
• RQ5 哪些材料因有利的电子和输运特性而表现出优异的热电性能？

主要发现

• 所有八种氢化单层材料（Si₂P, Si₂As, Si₂Sb, Si₂Bi, Ge₂P, Ge₂As, Ge₂Sb, Ge₂Bi）均通过结合能、声子色散和AIMD计算确认具有热力学和动力学稳定性。
• Si₂Y化合物具有间接带隙，而Ge₂Y化合物表现出直接带隙，且均具有适合光电子学应用的宽能带隙。
• Ge₂P和Si₂Sb单层材料表现出高载流子迁移率，显示出在高速纳米电子器件中的强潜力。
• Si₂Bi、Ge₂P和Si₂As单层材料因有利的电子输运特性而展现出有前途的热电性能。
• Si₂Sb和Si₂Bi单层材料具有合适的能带边位置和带隙，可在可见光下高效实现光催化分解水。
• 这些单层材料表现出强可见光吸收和显著的线性二向色性，使其非常适合用于太阳能电池和光束分离器件。