Electrical Resistance of a Point Defect

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****Technical Abstract****The electronic scattering, localization, and fluctuation associated with a point defect ultimately limit what is practically achievable in electronics. This NSF project uses new advances in materials and techniques to systematically measure the transport phenomena associated with single point defects in one-dimensional, carbon nanotube conductors. The one-dimensional limit dramatically amplifies the importance of single defects, to the extent that a single bond or atom modification can substantially affect two- or three-terminal device characteristics. This project will perform a comparative study of different types of defects, produced through deterministic chemical modification, in order to identify reproducible electronic features that can be associated with specific chemical terminations. Variable temperature conductance spectroscopy, scanning probe techniques, and noise spectroscopy will all be used to characterize devices before and after the incorporation of single point defects. The project will support the education of a Ph.D. student and also provide summer research opportunities for undergraduates and talented high school students. Because the field of research lies at the crossroads between traditional physics, chemistry, and electrical engineering, these research opportunities provide outstanding starting points for careers in science and technology.****Non-Technical Abstract****The copper wires that conduct most electricity are not very sensitive to a missing or misplaced atom. But imagine what happens when these wires shrink to nanometer scales. As the wire diameter approaches a few atoms, one missing atom could have enormous effects. New advances in materials and scientific tools allow us to actually make and study wires at this scale, along with more complicated electronic devices like transistors. For practical reasons, future electronics are more likely to use carbon wires than copper ones, so this project uses hollow carbon "nanotubes," wires having a cross section of only ten to twenty atoms. By fashioning these wires into transistors and then modifying carbon bonds one by one, the project will map out and understand the electronic consequences of disorder in atomic scale devices. This work is a "bottom-up" approach to understanding practical electronics at the smallest scales, and it will inform and enable the success of future electronics as traditional, "top-down" manufacturing shrinks to ever smaller scales. The project will support the education of a Ph.D. student and also provide summer research opportunities for undergraduates and talented high school students. Because the field of research lies at the crossroads between traditional physics, chemistry, and electrical engineering, these research opportunities provide outstanding starting points for careers in science and technology.