Abstract
Layered black phosphorus has drawn much attention due to the existence of a band gap compared to the widely known graphene. However, environmental stability of black phosphorus is still a major issue, which hinders the realization of practical device applications. Here, we spatially Raman map exfoliated black phosphorus using confocal fast-scanning technique at different time intervals. We observe a Raman intensity modulation for , B2g, and modes. This Raman modulation is found to be caused by optical interference, which gives insights into the oxidation mechanism. Finally, we examine the fabrication compatible PMMA coating as a viable passivation layer. Our measurements indicate that PMMA passivated black phosphorus thin film flakes can stay pristine for a period of 19 days when left in a dark environment, allowing sufficient time for further nanofabrication processing. Our results shed light on black phosphorus degradation which can aid future passivation methods.
Highlights
Discovered black phosphorus (B.P.) has been the focus of recent research for various device applications
A schematic representation of the experiment and the optical setup details of layered black phosphorus is illustrated in Fig. 1 and S1, respectively
We explore the degradation of exfoliated black phosphorus when coated with Polymethyl methacrylate (PMMA)
Summary
Discovered black phosphorus (B.P.) has been the focus of recent research for various device applications. Favron et al studied the degradation mechanism in few layers black phosphorus[23] Their results indicate phosphorene degrades in a short period of time, evident by the exponential decay in the intensity of each Raman mode. They found that the volume of phosphorene increases with time They reported etching of phosphorene layers accompanied the degradation process, which can be observed in the decreasing conductance of black phosphorus FET device. Wood et al showed that Al2O3 passivation is an effective method to prevent oxidation from ambient environment, preserving black phosphorus FET characteristics for a period of 2 weeks[25]. Another recent study shows that coating black phosphorus with trilayer graphene is required to prevent oxidation[26]. We examine the effectiveness of the widely-used photolithography compatible Polymethyl methacrylate (PMMA) polymer as a viable passivation layer in order to assess the allowed time for further lithography processing while preserving the pristine nature
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