Kumar Jeevesh, Shrivastava Mayank
Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore 560012, India.
ACS Omega. 2022 Jan 1;7(1):696-704. doi: 10.1021/acsomega.1c05353. eCollection 2022 Jan 11.
Despite its remarkable properties, phosphorene is not promising for device application due to its instability or gradual degradation under ambient conditions. The issue still persists, and no technological solution is available to address this degradation due to a lack of clarity about degradation dynamics at the atomic level. Here, we discuss atomic level degradation dynamics of phosphorene under ambient conditions while investigating the involvement of degrading agents like oxygen and water using density functional theory and first-principles molecular dynamics computations. The study reveals that the oxygen molecule dissociates spontaneously over pristine phosphorene in an ambient environment, resulting in an exothermic reaction, which is boosted further by increasing the partial pressure and temperature. The surface reaction is mainly due to the lone pair electrons of phosphorous atoms, making the degradation directional and spontaneous under oxygen atoms. We also found that while the pristine phosphorene is hydrophobic, it becomes hydrophilic after surface oxidation. Furthermore, water molecules play a vital role in the degradation process by changing the reaction dynamics path of the phosphorene-oxygen interaction and reducing the activation energy and reaction energy due to its catalyzing action. In addition, our study reveals the role of phosphorous vacancies in the degradation, which we found to act as an epicenter for the observed oxidation. The oxygen attacks directly over the vacant site and reacts faster compared to its pristine counterpart. As a result, phosphorene edges resembling extended vacancy are prominent reaction sites that oxidize anisotropically due to different bond angle strains. Our study clears the ambiguities in the kinetics of phosphorene degradation, which will help engineer passivation techniques to make phosphorene devices stable in the ambient environment.
尽管磷烯具有卓越的性能，但由于其在环境条件下的不稳定性或逐渐降解，它在器件应用方面并不具有前景。这个问题仍然存在，并且由于在原子水平上缺乏对降解动力学的清晰认识，目前还没有技术解决方案来解决这种降解问题。在这里，我们利用密度泛函理论和第一性原理分子动力学计算，讨论了磷烯在环境条件下的原子水平降解动力学，同时研究了氧气和水等降解剂的作用。研究表明，在环境中，氧分子会在原始磷烯上自发解离，导致放热反应，增加分压和温度会进一步促进该反应。表面反应主要归因于磷原子的孤对电子，使得降解在氧原子作用下具有方向性和自发性。我们还发现，虽然原始磷烯是疏水的，但表面氧化后它会变成亲水的。此外，水分子在降解过程中起着至关重要的作用，它通过改变磷烯 - 氧相互作用的反应动力学路径，并由于其催化作用降低活化能和反应能。此外，我们的研究揭示了磷空位在降解中的作用，我们发现它是观察到的氧化的中心。氧直接攻击空位，并且与原始对应物相比反应更快。因此，类似于扩展空位的磷烯边缘是突出的反应位点，由于不同的键角应变而发生各向异性氧化。我们的研究消除了磷烯降解动力学中的模糊性，这将有助于设计钝化技术，使磷烯器件在环境中保持稳定。
