First-Principles Molecular Dynamics Insight into the Atomic Level Degradation Pathway of Phosphorene

Abstract

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.

Memory effect and coexistence of negative and positive photoconductivity in black phosphorus field effect transistor for neuromorphic vision sensors

“…28 Studies indicate that oxidation is triggered by interactions with oxygen (O 2 ), as water (H 2 O) alone does not appear to react with pristine BP, although it may catalyze O 2 induced oxidation. 29,30 While the interaction of pristine BP with H 2 O has been extensively explored, the study of the hydrophilicity of oxidized BP is limited to the effects of localized O 2 atoms chemisorbed on the surface. 29,31 Consequently, exposure of BP to air results in moisture absorption, leading to modifications in both physical and chemical properties 31,32 and, ultimately, to the degradation of its electronic properties.…”

Interaction of Water and Oxygen Molecules with Phosphorene: An Ab Initio Study

“…Phosphorene usage in the above-described fields is, however, jeopardized by its strong tendency to degrade under ambient conditions [17][18][19][20][21]. The atomic-scale mechanisms of oxidation of phosphorene have been investigated theoretically [22][23][24][25][26] and experimentally [18,27,28], giving rise to different interpretations of the role played by water. Ultimately, oxidation was found to be induced by the interaction with O 2 , whereas water alone does not seem to react with pristine phosphorene, even if it may act as a catalyst for O 2 -induced oxidation [18,22].…”

“…The atomic-scale mechanisms of oxidation of phosphorene have been investigated theoretically [22][23][24][25][26] and experimentally [18,27,28], giving rise to different interpretations of the role played by water. Ultimately, oxidation was found to be induced by the interaction with O 2 , whereas water alone does not seem to react with pristine phosphorene, even if it may act as a catalyst for O 2 -induced oxidation [18,22]. While the interaction of pristine phosphorene with water has been extensively explored [29], the study of the hydrophilicity of oxidized phosphorene is limited to the effects of localized oxygen atoms chemisorbed on the surface [18,22,26,30], although an understanding of the hydrophilic behavior of fully oxidized layers would be important for most applications.…”

Breathing Mode’s Temperature Coefficient Estimation and Interlayer Phonon Scattering Model of Few-Layer Phosphorene

“…Phosphorene, a few layers (ideally monolayer) of black phosphorous, consists of various remarkable properties, which make the material a promising candidate for next-generation electronic devices. − However, many material features are unexplored yet, probably due to its ambient instability. , Identifying a thin flake of phosphorene is a real challenge for material exploration and device processing due to the risk of degradation during thickness measurement using tools such as AFM . Low-frequency Raman active interlayer phonon modes, known as breathing modes, can provide a promising non-destructive technique to determine thin flakes from the exfoliated 2D materials’ flake islands. − The phonon mode corresponds to interlayer out-of-the-plane vibration in a few layers of black phosphorous.…”

“… 1 − 3 However, many material features are unexplored yet, probably due to its ambient instability. 4 , 5 Identifying a thin flake of phosphorene is a real challenge for material exploration and device processing due to the risk of degradation during thickness measurement using tools such as AFM. 6 Low-frequency Raman active interlayer phonon modes, known as breathing modes, can provide a promising non-destructive technique to determine thin flakes from the exfoliated 2D materials’ flake islands.…”