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Black phosphorus is one of the most stable allotropes of phosphorus, and its unique two-dimensional lamellar structure makes it have many excellent properties. The two-dimensional multilayer crystal structure of black phosphorus is similar to graphene, and the lamellar layer is bonded to each other by Van der Waals bonding. In early research, it is easy to tear off the nano-level black phosphorus by mechanical exfoliation process and the nano-level black phosphorus is called phosphorene. The band gap of phosphorene changes because of different numbers of its layers, and the adjustable range of band gap is greater than any of today’s transitional metal disulfide. Meanwhile, phosphorene is applied to electronic components with a high on-off ratio of 105, and carrier mobility of ~ 1000 cm2/Vs, both of which are excellent features required as logic devices. Phosphorene is a remarkable and novel two-dimensional material expected to replace silicon as the transporting channel of the semiconducting device.
However, in the past studies, black phosphorus was prone to be oxidized easily in the atmosphere and this phenomenon was obviously observed on the few layers phosphorene, which results in deterioration of its intrinsic electrical transport properties. How to protect the black phosphorus without oxidation and maintain the excellently electrical property is an important issue. In addition, the process to quantify the synthesis of phosphorene is few to be researched, while the material properties are still at the researching stage.
In this study, we obtained phosphorene by liquid phase exfoliation, and analyzed its material properties and stability. We used different solvents as exfoliation medium, and found that 1% sodium dodecyl sulfate (SDS) dissolved in deoxygenated water solvent can get a high productivity. The thickness of few layered phosphorene is about 6 nm. The uniformity in thickness of exfoliated phosphorene with SDS solvent is better than it with other solvents.
In addition, the deterioration rate of phosphorene could be restrained by encapsulating electrochemical graphene with its excellent resistance of water and oxygen. The solution was prepared by mixing the solution with dimethylformamide (DMF) as the dispersion of phosphorene and graphene. Therefore, high quality phosphorene can be obtained by optimizing this synthesis method, the production of. Our study also demonstrates a process for the assembly of the phosphorene into a continuous film which is effective in retarding the oxidation of the phosphorene. The surface of the phosphorene film can maintain the intrinsic state, so that phosphorene can be protected within 60 days from the impact of oxidation. It is attractive and has benefit to form the continuous and large area film with a few layers of phosphorene for the applications of electrical devices in the future. | en_US |