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| Black phosphorus | |
|---|---|
| Name | Black phosphorus |
| Other names | Phosphorus (black) |
| Molar mass | 30.974 g·mol−1 |
| Appearance | Black crystalline solid |
| Density | 2.69 g·cm−3 |
| Melting point | 863 °C (sublimes) |
| Crystal system | Orthorhombic |
| Space group | Cmca |
Black phosphorus is the most thermodynamically stable allotrope of the element phosphorus at low temperature and ambient pressure, notable for its layered structure and semiconducting properties. It has attracted attention across materials science, condensed matter physics, and nanoelectronics for its tunable band gap, high carrier mobility, and anisotropic transport, motivating research in laboratories, universities, and corporations worldwide.
Black phosphorus is a crystalline allotrope of phosphorus related historically and chemically to white phosphorus, red phosphorus, and violet phosphorus and studied by chemists such as Humphry Davy, Antoine Lavoisier, and later solid‑state researchers in the 19th century. Its layered puckered sheets support exfoliation into few‑layer and monolayer forms used in experiments at institutions including Massachusetts Institute of Technology, University of Cambridge, Stanford University, Harvard University, and national laboratories like Lawrence Berkeley National Laboratory. The material has driven cross‑disciplinary collaborations among groups at IBM, Intel, Samsung, and startup companies exploring 2D semiconductors for electronics, photonics, and energy applications.
The conversion of red or white phosphorus to a black, more stable phase was first reported in the mid‑19th century in publications that circulated among chemists in France, Germany, and the United Kingdom. Early experimentalists such as Marcellin Berthelot and researchers affiliated with institutions like the Royal Society and the German Chemical Society investigated the pressure and heat conditions necessary to produce crystalline phosphorus. Systematic characterizations emerged in the 20th century via spectroscopists and crystallographers from universities including University of Oxford, University of Göttingen, University of Tokyo, and facilities like the National Institute of Standards and Technology and Argonne National Laboratory.
Black phosphorus is an elemental solid with anisotropic mechanical, thermal, and electrical behavior. Its density, hardness, and thermal conductivity have been measured by research groups at Max Planck Society institutes and universities such as ETH Zurich and University of California, Berkeley. Chemical reactivity contrasts with the pyrophoric behavior of white phosphorus; black phosphorus resists spontaneous ignition and displays distinct oxidation pathways studied by researchers at California Institute of Technology, University of Illinois Urbana‑Champaign, and Columbia University. Spectroscopic signatures have been catalogued using techniques developed at facilities like CERN, SLAC National Accelerator Laboratory, and synchrotrons hosted by Diamond Light Source and European Synchrotron Radiation Facility.
The orthorhombic crystal structure of black phosphorus (space group Cmca) consists of puckered layers of phosphorus atoms forming six‑membered rings; structural elucidation employed X‑ray diffraction at institutions such as Brookhaven National Laboratory, Los Alamos National Laboratory, and university crystallography groups at University of Cambridge and University of Chicago. Allotropic relationships to rhombohedral and fibrous forms were clarified by mineralogists and solid‑state chemists associated with the Smithsonian Institution and the Natural History Museum, London. The monolayer derivative, often called phosphorene in the literature, has been characterized using microscopy labs at National Institute for Materials Science (Japan), Korea Advanced Institute of Science and Technology, and Tsinghua University.
Historically, preparation of black phosphorus involved subjecting white or red phosphorus to high pressure and high temperature in sealed vessels—a technique refined in laboratories at Carnegie Institution for Science and Russian Academy of Sciences. Modern methods include mineralizer‑assisted growth using tin‑iodine or bismuth fluxes developed in research groups at Tohoku University, University of Colorado Boulder, and industrial labs at Rohm and Haas affiliates. Exfoliation techniques to obtain few‑layer sheets employ mechanical cleavage pioneered in experiments at University of Manchester and liquid‑phase approaches optimized at University of California, Santa Barbara and startups collaborating with DARPA‑funded programs.
Black phosphorus exhibits a direct band gap that varies with thickness, measured by spectroscopists at Bell Labs, NIST, and university optics groups at University of Pennsylvania and Yale University. Charge carrier mobilities and anisotropic transport were quantified in studies conducted at University of Texas at Austin, Purdue University, and École Polytechnique Fédérale de Lausanne. Nonlinear optical responses, excitonic effects, and valley physics were probed by collaborations involving Max Planck Institute for Solid State Research, Riken, and the National Graphene Institute. Device demonstrations often reference benchmarking work from Intel Labs, Google research teams, and spin‑out ventures from Stanford and MIT.
Potential applications span field‑effect transistors, photodetectors, flexible electronics, thermoelectrics, and sensors, with prototypes developed by consortia including SEMATECH, IMEC, and corporate labs at Samsung Electronics and TSMC. Energy‑conversion research linking black phosphorus to Duke University, Imperial College London, and industrial partners explores photocatalysis and battery electrodes. Integration into heterostructures with graphene, molybdenum disulfide, and other 2D materials has been pursued by groups at University of Manchester, Columbia University, and National University of Singapore.
Surface oxidation and degradation under ambient oxygen and moisture present challenges identified by teams at University of California, Los Angeles, University of Michigan, and University of Toronto. Passivation strategies—encapsulation with hexagonal boron nitride, atomic layer deposition of oxides, and functionalization methods—were developed in laboratories at IBM Research, Intel Corporation, Lawrence Livermore National Laboratory, and academic groups at University of Washington and Seoul National University. Standards for handling and storage are informed by safety practices from Occupational Safety and Health Administration guidelines and protocols at research institutions such as Johns Hopkins University and Scripps Research.