Investigating Ultrasonicated Allotropes of Phosphorus

Samuel Thomas Moran, Avinash Nayak, Mark Barron, Umair Khakoo, Deji Akinwande


Two-dimensional (2D) materials have emerged as post silicon semiconductors that may positively impact future electronic technologies. Elemental phosphorus exists in four allotropes each having different properties including white, red, violet, and black. Of the four allotropes, black phosphorus (black P) is a crystalline lattice of phosphorus atoms which can be exfoliated into 2D layers due to the structure of in-plane covalent bonds and out-of-plane van der Waals forces. Black P is a recent elemental 2D material that has been discovered; it has a layer dependent band gap between 0.3eV (bulk) and 2.0eV (monolayer phosphorene). Currently, using standard synthesis techniques, a stable form of black P has been challenging and expensive to synthesize. In this investigation, red P was successfully transformed into black P as a result of ultrasonic irradiation. The process of ultrasonication involves resonating high frequency sound waves in a solution to create cavitation bubbles which implode to create high temperature (~5000K) and pressure (~8GPa) on a very local area (~2 to 5 microns) within the solution. This high frequency ultrasonic exposure to phosphorus results in change in color from red to black and a prominent A2g Raman peak which is observed in black P. 


Black Phosphorus, Ultrasonication, Liquid Synthesis, High Pressure, High Temperature

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