July 14, 2017 A density functional theory calculation showed the magnetic properties of a fluorinated sample of hexagonal boron nitride. This version is ferromagnetic, determined by how the fluorine atoms (red) attach to the boron and nitrogen matrix. Credit: Ajayan Group\/Rice University <\/p>\n
A little fluorine turns an insulating ceramic known as white graphene into a wide-bandgap semiconductor with magnetic properties. Rice University scientists said that could make the unique material suitable for electronics in extreme environments. <\/p>\n
A proof-of-concept paper from Rice researchers demonstrates a way to turn two-dimensional hexagonal boron nitride (h-BN) - aka white graphene - from an insulator to a semiconductor. The magnetism, they said, is an unexpected bonus. <\/p>\n
Because the atomically thin material is an exceptional conductor of heat, the researchers suggested it may be useful for electronics in high-temperature applications, perhaps even as magnetic memory devices. <\/p>\n
The discovery appears this week in Science Advances. <\/p>\n
\"Boron nitride is a stable insulator and commercially very useful as a protective coating, even in cosmetics, because it absorbs ultraviolet light,\" said Rice materials scientist Pulickel Ajayan, whose lab led the study. \"There has been a lot of effort to try to modify its electronic structure, but we didn't think it could become both a semiconductor and a magnetic material. <\/p>\n
\"So this is something quite different; nobody has seen this kind of behavior in boron nitride before,\" he said. <\/p>\n
The researchers found that adding fluorine to h-BN introduced defects into its atomic matrix that reduced the bandgap enough to make it a semiconductor. The bandgap determines the electrical conductivity of a material. <\/p>\n
\"We saw that the gap decreases at about 5 percent fluorination,\" said Rice postdoctoral researcher and co-author Chandra Sekhar Tiwary. The gap gets smaller with additional fluorination, but only to a point. \"Controlling the precise fluorination is something we need to work on. We can get ranges but we don't have perfect control yet. Because the material is atomically thin, one atom less or more changes quite a bit. <\/p>\n
\"In the next set of experiments, we want to learn to tune it precisely, atom by atom,\" he said. <\/p>\n
They determined that tension applied by invading fluorine atoms altered the \"spin\" of electrons in the nitrogen atoms and affected their magnetic moments, the ghostly quality that determines how an atom will respond to a magnetic field like an invisible, nanoscale compass. <\/p>\n
\"We see angle-oriented spins, which are very unconventional for 2-D materials,\" said Rice graduate student and lead author Sruthi Radhakrishnan. Rather than aligning to form ferromagnets or canceling each other out, the spins are randomly angled, giving the flat material random pockets of net magnetism. These ferromagnet or anti-ferromagnet pockets can exist in the same swatch of h-BN, which makes them \"frustrated magnets\" with competing domains. <\/p>\n
The researchers said their simple, scalable method can potentially be applied to other 2-D materials. \"Making new materials through nanoengineering is exactly what our group is about,\" Ajayan said. <\/p>\n
Co-authors of the paper are graduate students Carlos de los Reyes and Zehua Jin, chemistry lecturer Lawrence Alemany, postdoctoral researcher Vidya Kochat and Angel Mart, an associate professor of chemistry, of bioengineering and of materials science and nanoengineering, all of Rice; Valery Khabashesku of Rice and the Baker Hughes Center for Technology Innovation, Houston; Parambath Sudeep of Rice and the University of Toronto; Deya Das, Atanu Samanta and Rice alumnus Abhishek Singh of the Indian Institute of Science, Bangalore; Liangzi Deng and Ching-Wu Chu of the University of Houston; Thomas Weldeghiorghis of Louisiana State University and Ajit Roy of the Air Force Research Laboratories at Wright-Patterson Air Force Base. <\/p>\n
Ajayan is chair of Rice's Department of Materials Science and NanoEngineering, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry. <\/p>\n
Explore further: Graphene foam gets big and tough: Nanotube-reinforced material can be shaped, is highly conductive <\/p>\n
More information: \"Fluorinated h-BN as a magnetic semiconductor\" Science Advances (2017). DOI: 10.1126\/sciadv.1700842 , http:\/\/advances.sciencemag.org\/content\/3\/7\/e1700842<\/a><\/p>\n Journal reference: Science Advances <\/p>\n Provided by: Rice University <\/p>\n A chunk of conductive graphene foam reinforced by carbon nanotubes can support more than 3,000 times its own weight and easily bounce back to its original height, according to Rice University scientists. <\/p>\n (Phys.org) Nanoengineering researchers at Rice University and Nanyang Technological University in Singapore have unveiled a potentially scalable method for making one-atom-thick layers of molybdenum diselenidea highly ... <\/p>\n Developing novel materials from the atoms up goes faster when some of the trial and error is eliminated. A new Rice University and Montreal Polytechnic study aims to do that for graphene and boron nitride hybrids. <\/p>\n A new center at Rice University and Pennsylvania State University will study, in collaboration with industry, the development of atom-thin two-dimensional coatings for a variety of uses. <\/p>\n Rice University researchers have modeled a nanoscale sandwich, the first in what they hope will become a molecular deli for materials scientists. <\/p>\n The same slip-and-stick mechanism that leads toearthquakesis at work on the molecular level in nanoscale materials, where it determines the shear plasticity of the materials, according to scientists at Rice University ... <\/p>\n A little fluorine turns an insulating ceramic known as white graphene into a wide-bandgap semiconductor with magnetic properties. Rice University scientists said that could make the unique material suitable for electronics ... <\/p>\n Scientists from the Swiss Nanoscience Institute and the University of Basel have succeeded in coupling an extremely small quantum dot with 1,000 times larger trumpet-shaped nanowire. The movement of the nanowire can be detected ... <\/p>\n For more than 60 years, researchers have tried to successfully cryopreserve (or freeze) the embryo of zebrafish, a species that is an important medical model for human health. In a new study, researchers at the University ... <\/p>\n Antibiotic resistance is a growing problem, especially among a type of bacteria that are classified as \"Gram-negative.\" These bacteria have two cell membranes, making it more difficult for drugs to penetrate and kill the ... <\/p>\n Visualizing biological cells under a microscope was just made clearer, thanks to research conducted by graduate student Yifei Jiang and principal investigator Jason McNeill of Clemson University's department of chemistry. <\/p>\n Early phase Northwestern Medicine research has demonstrated a potential new therapeutic strategy for treating deadly glioblastoma brain tumors. <\/p>\n Please sign in to add a comment. Registration is free, and takes less than a minute. Read more <\/p>\n <\/p>\n Read the original here:<\/p>\n Fluorine grants white graphene new powers: Researchers turn ... - Phys.Org<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" July 14, 2017 A density functional theory calculation showed the magnetic properties of a fluorinated sample of hexagonal boron nitride. This version is ferromagnetic, determined by how the fluorine atoms (red) attach to the boron and nitrogen matrix. Continue reading