Degradation of Black Phosphorus and Strategies to Enhance Its Ambient Lifetime

Abstract

water resulting in rapid decomposition, [12] making processing of the material challenging and resulting in detrimental effects on its optical and electronic properties. [13] The ambient degradation of BP presents a significant hurdle to realizing the full potential of BP in various applications. The successful application of BP will rely either on its exclusion from the factors that contribute to its degradation or protection methods that prevent its degradation in ambient conditions. Literature reports that have studied the degradation chemistry of BP have revealed some conflicting results regarding the effect of water, oxygen and light, indicating that BP has a complex surface chemistry. The indepth characterization of BP degradation is critical for the development of new protection strategies and progress of the material and its applications. The role of the surface oxide as a passivation layer that stabilizes BP has also created some debate between researchers. Although a stabilizing oxide has been reported in theoretical studies, [14] experimental reports question the challenges of creating a self-limiting surface oxide on BP. [15] Protection of BP can also be accomplished by capping layers, [13c,16] functionalization, [17] solvent passivation, [10b] or the incorporation of polymers. [18] Ambient degradation can be suppressed by covalent functionalization where chemical binding of molecules to the reactive lone pairs on the surface prevent decomposition. [17] Noncovalent functionalization can also be employed, which inhibits degradation by passivating BP nanoflakes through noncovalent interactions. [17b] Solvent passivation forms a protective barrier against oxidants while polymer coatings, or the formation of BP-polymer hybrids enhances its oxidation resistance while also modifying its properties. This review outlines the factors that influence the oxidation of BP from a surface chemistry perspective, including the effect of water, oxygen, and light on the degradation of BP, as well as elucidation of the oxidation mechanism through analysis of BP exposed to single oxidants and evaluation of the oxidation products. Additionally, an overview of current advances in the protection strategies for BP is presented. 2. Structure, Properties, and Exfoliation of BP BP has an orthorhombic crystal structure and consists of layers of phosphorene held together by van der Waals interactions, as depicted in Figure 1a. [19] The individual layers of phosphorene consist of phosphorus atoms covalently bound Exfoliation of black phosphorus (BP) into phosphorene has led to the discovery of its semiconducting properties and tunable bandgap, enabling its use in a range of applications including transistors, batteries, and sensors. However, BP's ambient instability poses a considerable challenge to its incorporation into functional devices. Observed changes to the surface chemistry of BP during degradation has recently provided insight into the degradation pathways. In this review, degradation mechanisms are discussed including th...

Long-term environmental stability of nitrogen-healed black phosphorus

“…and 𝐵 2𝑔 vibrational modes have all been identified as signatures of the oxidation and degradation, as well as a shift in the peak position. [23,26,27,29,34,50,60,61] However, in our analysis (data not shown), we do not see a clear Raman signature for degradation in our samples, suggesting that Raman spectroscopy may not be the best tool to characterize the BP degradation. Therefore, we evaluate the environmental stability by AFM, as previous works have shown that the oxidation increases the BP surface roughness [31,50] and crystal volume.…”

“…The elemental P peaks can be observed at ̴ 130 eV, [65] while the peak ̴ 135 eV is attributed to oxides species (P-O), where P2O5 is suggested to be the most stable form. [29] The broad peak around ̴ 127 eV originates from the s photoelectron Si satellite from the substrate. [22] For the control sample, we can observe a relative decrease in intensity of the elemental P peaks, followed by an increase in the relative amount of oxides species.…”

“…[23][24][25][26][27] Physical and chemical approaches have been used both to improve the BP stability in air and modulate its properties. [28,29] The coating with Al2O3 by atomic layer deposition [22,30,31] or other LMs, such as hexagonal boron nitride (hBN) and graphene, [32][33][34][35] are examples of physical passivation. The chemical functionalization is also an efficient way to protect BP and to manipulate its chemical and electronic properties.…”

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

“… 1 − 3 However, the material is unsuitable for electronic and optoelectronic applications due to a lack of stability in the ambient environment. 4 Some of the engineering approaches like encapsulation, 5 pulsed laser exfoliation, 6 solvent passivation, 7 and oxygen plasma etching 8 have guided to make the material stable. The methods, however, are not very promising for long-term stability, which is a real challenge in terms of material growth, device processing, and packaging for such applications.…”

Directly Evaluating the Optical Anisotropy of Few‐Layered Black Phosphorus during Ambient Oxidization

“…[15] With water involved, the oxidization process becomes much more complex, and the precise roles of water, oxygen, and light are still unclear and in active debate with different mechanisms, such as the oxidization behaviors that took place in water solvent and moisture atmosphere result in different degradation products. [16][17][18][19][20] One of the oxidization mechanisms is reported that the water molecular (humidity) exhibits catalyzed function that first lowers the reaction energy between BP and oxygen, [12] and then reacts with phosphorus oxides forming phosphorus acid, which accelerates the oxidization and etching speed. [11,12,21] An alternative mechanism was proposed by Hu et al, who revealed the BP oxidization occurred even in the dark environment with the coexistence of water and oxygen, which was attributed to the polarization effect of water that lowers the energy level of oxygen, resulting in acceleration of electron transfer from BP to oxygen that triggers BP oxidization.…”