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In this electron microscope image of bismuth atoms (circled) in a silicon crystal, white dotted circles indicate bismuth atoms that have been moved into positions to form an ordered array while green dotted circles show bismuth atoms that have yet to be moved to complete the array. The scale bar is one nanometer, or a billionth of a meter. Credit: Bethany Hudak/Oak Ridge National Laboratory, U.S. Dept. of Energy
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ORNL’s Bethany Hudak places a crystal sample in an aberration-corrected scanning transmission electron microscope. Her team was able to selectively position bismuth atoms in the bulk of a crystal below its surface—a feat that has implications for constructing future quantum computers. Credit: Genevieve Martin/Oak Ridge National Laboratory, U.S. Dept. of Energy
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In this electron microscope image of bismuth atoms (circled) in a silicon crystal, white dotted circles indicate bismuth atoms that have been moved into positions to form an ordered array while green dotted circles show bismuth atoms that have yet to be moved to complete the array. The scale bar is one nanometer, or a billionth of a meter. Credit: Bethany Hudak/Oak Ridge National Laboratory, U.S. Dept. of Energy
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ORNL’s Bethany Hudak places a crystal sample in an aberration-corrected scanning transmission electron microscope. Her team was able to selectively position bismuth atoms in the bulk of a crystal below its surface—a feat that has implications for constructing future quantum computers. Credit: Genevieve Martin/Oak Ridge National Laboratory, U.S. Dept. of Energy
September 4, 2018 - An Oak Ridge National Laboratory-led team used a scanning transmission electron microscope to selectively position single atoms below a crystal’s surface for the first time. “We’re moving individual dopants where we want them to go,” said Bethany Hudak of ORNL. “Direct atom positioning represents one step toward realizing the single-atom devices potentially needed to build future quantum computers.” The researchers grew a crystal consisting of silicon atoms but containing a few bismuth atoms. The bismuth atoms’ larger size caused strain on the lattice framework of the crystal. Then, they developed a method to employ the microscope’s electron beam to selectively hit a column of silicon atoms with enough energy to eject one from its lattice position, enabling a bismuth atom to slide into the vacant spot. Next steps for the work, which was published in ACS Nano, include controlling atom placement at different crystal depths and programming the electron microscope to create specific shapes.
