Dr. Saw-Wai Hla
Dr. Saw-Wai Hla, Professor of Physics at Ohio University, is part of a team of researchers from the U.S. Department of Energy’s Argonne National Laboratory, Ill., and Ohio University that has devised a powerful technique that simultaneously resolves the chemical characterization and topography of nanoscale materials down to the height of a single atom, reports ASM International in a report on “Instrument set to revolutionize materials characterization.”
Ohio University physics graduate students Heath Kersell and Yang Li helped to conduct the experiments.
Revolutionary Materials Characterization
The technique combines synchrotron x-rays (SX) and scanning tunneling microscopy (STM). In experiments, researchers used SX as a probe and a nano-fabricated smart tip of a STM as a detector.
Using this technique, researchers detected the chemical fingerprint of individual nickel clusters on a copper surface at a two-nanometer (nm) lateral resolution, and at the ultimate single atom height sensitivity. By varying the photon energy, researchers used the difference in photoabsorption cross sections for nickel and the copper substrate to chemically image a single-nickel nanocluster, thus opening the door to new opportunities for chemical imaging of nanoscale materials. Until now, a spatial limit of about only 10-nm was attainable, and researchers had to simultaneously sample a large sample area. The spatial resolution was improved to 2 nm.
“Imaging with direct chemical sensitivity has been a long-standing goal since scanning tunneling microscopes were developed during the 1980s,” said Volker Rose, physicist in the x-ray science division. “It was very exciting when we obtained elemental contrast of a material at just one atomic layer height.”
“This is a marriage between two of the most powerful instruments of materials science,” said Saw-Wai Hla, electronic and magnetic materials and devices group leader in Argonne’s Nanoscience & Technology Division. “We now have an instrument that can perform the functions of STM and x-rays in a single setting, and therefore it has a great potential to revolutionize the materials characterization.”
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