Abstract
In this work, oxidation processes are correlated with the current-voltage characteristics of few-layer black phosphorus obtained by liquid-phase exfoliation. Black phosphorous (BP), a room-temperature p-type semiconductor, exhibits an anomalous switching behavior between 373 and 448 K. The anomalous increase in electrical resistance is explained using a combined spectroscopic and DFT approach. The activation energy for thermally activated electrical conductance was calculated from the current-voltage characteristics and correlated with the oxidation processes. The activation energy for thermally activated electrical conductance in the dangling oxide BP phase was found to be 79.7 meV, ∼40 times lower than that in the interstitial counterpart. First-principles calculations reveal electronic differences between dangling and interstitial oxides, and electrical resistance measurements reveal a Schottky-to-ohmic contact formation related to the differences in the calculated work function of dangling and interstitial oxides. We propose that this phenomenon can be exploited as a fast, economical method for the evaluation of the oxidation processes in few-layer BP. ©
Highlights
Few-layer black phosphorus has attracted considerable interest since 2014, as demonstrated by the 700+ papers published in this field in 2019 alone
The energy barrier for the formation of the transition state during the oxidation of the black phosphorus monolayer is the lowest (i.e., 0.1−0.5 eV)[14,15] in comparison with other 2D materials. This disadvantage will be an obstacle for the industrial application of black phosphorus unless a deeper understanding of the oxidation of 2D materials and better control of the process is achieved.[19−23] It would be highly desirable to avoid repeating the fate of graphene, for which quality and standardization issues have emerged as barriers for the industrial application regardless of the academic enthusiasm for the beauty of the science involved
Several models of phosphorene oxide (BPox) have been proposed[15,21,26,28] including the following metastable oxides: dangling oxygen, when the oxygen atom is chemically bonded on the surface to one single phosphorus atom; oxygen bridge, for the oxygen atom chemically bonded to two consecutive phosphorus atoms, and interstitial oxygen when the oxygen atom penetrates the lattice
Summary
Few-layer black phosphorus has attracted considerable interest since 2014, as demonstrated by the 700+ papers published in this field in 2019 alone. Phosphorene is a stable monoelement twodimensional (2D) p-type semiconductor with potential applications in broadband photoresponse field-effect transistors (FETs)[1] and sensors (e.g., NO2,2,3 NH3,4 humidity,[5] and biomolecules[6]) These applications rely on the charge transfer process between black phosphorus and metal electrodes. The energy barrier for the formation of the transition state during the oxidation of the black phosphorus monolayer is the lowest (i.e., 0.1−0.5 eV)[14,15] in comparison with other 2D materials (e.g., graphene: 2.2−2.7 eV,[16] MoS2:1.6 eV,[17] and h-BN: 1.2−2.6 eV18) This disadvantage will be an obstacle for the industrial application of black phosphorus unless a deeper understanding of the oxidation of 2D materials and better control of the process is achieved.[19−23] It would be highly desirable to avoid repeating the fate of graphene, for which quality (e.g., defects) and standardization issues have emerged as barriers for the industrial application regardless of the academic enthusiasm for the beauty of the science involved
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