Electronic Fluctuation and Localization at Point Defects

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Technical:This single investigator research program systematically investigates transport phenomena associated with single point defects. The electronic scattering, localization, and fluctuation associated with a point defect ultimately limit what is practically achievable in electronics, and industry's ability to design and build electronic circuits at ever smaller scales is limited by control over these sites. While such topics have been extensively treated theoretically, few experimental platforms are available for making direct measurements. In this project, the experimental platform consists of one-dimensional conduction through single-walled carbon nanotubes. In this one-dimensional limit, the alteration of single bonds is sufficient to dramatically alter electronic behavior, providing a window into the transport regime where atomic-scale effects become measurable, distinguishable, and reproducible. The measurement of nanotube circuits both before and after defect creation very directly identifies the interplay between point defects and electronic effects, in order to map out reproducible electronic features associated with different chemical terminations. By using conductance spectroscopy, local scanning probe techniques, noise spectroscopy, optical spectroscopy, and in situ characterization during annealing, this project aims to complete a controlled and systematic study relevant to nanoscale physics and the semiconductor industry. Furthermore, all of the work will be completed by graduate and undergraduate students in a training environment designed to expose junior researchers to problems and techniques relevant to future careers in science.Non-Technical:Modern transistors, memory elements, and all of the wiring that connects them continue to shrink from one generation of products to the next. In extreme cases, the films of material that make up these circuit elements are already only a few atoms thick. The semiconductor industry anticipates that, in the near future, more and more devices will cross into this limit where success or failure can depend on the accidental presence or absence of individual atom. In order to forecast what kinds of effects science and industry will observe in this limit, this project fabricates and tests electronic circuits that intentionally contain single atomic defects. The experimental platform, which uses carbon nanotube conductors only a few atoms wide, directly accesses the limit where atomic scale effects can become measurable, distinguishable, and reproducible. Undergraduate and graduate students are trained to test nanotube circuits before and after the incorporation of single atomic defects, and to identify the electronic changes that result. This degree of control allows the electronic consequences of atomic defects to be systematically investigated and, through further chemical tailoring, corrected for in practical devices. Combined with a unique educational program in Materials Physics, this project provides junior researchers with both practical and theoretical understanding of looming issues in next generation electronic devices, and the relevant techniques for solving them.