Designed to be the most accurate commercially available “meter stick” for the nano world, the new measuring tool—a calibration standard for X-ray diffraction—boasts uncertainties below a femtometer. That’s 0.000 000 000 000 001 meter, or roughly the size of a neutron.
The new ruler is in the form of a thin, multilayer silicon chip 25 millimeters square (just under an inch). Each one is individually measured and certified by NIST for the spacing and angles of the crystal planes of silicon atoms in the base crystal.
X-ray diffraction works by sending X-rays through a crystal—which could be anything from a wafer used to make microchips to a crystallized sample of an unknown protein—and observing the patterns made by the X-rays as they diffract from electrons in the crystal. The spacing, angles and intensity of the pattern’s lines tell a trained crystallographer the relative positions of the atoms in the crystal, as well as something about the quality of the crystal, the nature of the chemical bonds and more. It is one of the workhorse techniques of materials science and engineering. The precision version, high-resolution X-ray diffraction, can be used to determine the thickness, crystal structure, embedded strain and orientation of thin films used in advanced semiconductor devices and nanotechnologies.
Formally NIST Standard Reference Material (SRM) 2000, “Calibration Standard for High-Resolution X-Ray Diffraction,” the new ruler gives crystallographers an extremely well-known crystal sample for calibrating their precision instruments. It was made possible by the development of a unique parallel beam diffractometer at NIST that makes measurements traceable to international measurement standards and is believed to be the most accurate angle measuring device of its kind in the world. The NIST instrument can measure angles with an accuracy better than an arc second, 1/3600 of a degree. “Our accuracy is at about the angle made by the diameter of a quarter—if you’re looking at it from two miles away,” explains NIST materials scientist Donald Windover, “The precision is better, about the size of Washington’s nose.”
Because the crystal lattice values for SRM 2000—spacing, tilt, orientation—are traceable to SI units, the new material provides an absolute reference for high-precision calibrations. Details are available at https://www-s.nist.gov/srmors/view_detail.cfm?srm=2000.
Standard Reference Materials are among the most widely distributed and used products from NIST. The agency prepares, analyzes and distributes more than a thousand different materials that are used throughout the world to check the accuracy of instruments and test procedures used in manufacturing, clinical chemistry, environmental monitoring, electronics, criminal forensics and dozens of other fields. For more information, see NIST’s SRM Web page at http://ts.nist.gov/measurementservices/referencematerials
Michael Baum | Newswise Science News
Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst
Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
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In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
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