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Illustrations
Acknowledgments
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One of the major dynamics on which the design of the STM is based relies on the interactions between a conductive surface (composed of a metal, for example) and the microscope tip, as the tip does not contact the surface, but remains about a nanometer away (Mantooth 9). Instead of contact, the interaction between tip and surface is a result of electron tunneling. Tunneling is based on the articulation of electrons as both particles and waves in quantum mechanics, where “each electron behaves like a wave: its position is ‘smeared out’” (Binnig and Rohrer, “The Scanning Tunneling Microscope” 52). The behavior of electrons as both particles and waves allows surface electrons to “tunnel” through the barrier of the vacuum between surface and tip atoms, and thus interact with the electron cloud of the atoms or atoms on the tip. Measurements of the tip’s electron clouds through voltage thus presents a way to understand the surface atoms through the behavior of the behavior of the atoms. Use of electron tunneling as a measurement technique in the STM is part of a broader trend in creating images from non-optical data, and has implications for what is able to be visualized with the instrument.
Electron tunneling is a relatively new idea; the incorporation of electron tunneling into the STM shows how the dynamic fits into the larger story of the development of non-lens-based visualization technologies. In 1960, Ivar Giaever first published the results of demonstrated electron tunneling (Giaver 147–48). For his research, he received the Nobel Prize in 1973. However, scientists did not apply electron tunneling to instrument development until the early 1970s, when Russell Young, John Ward, and Fredric Scire created a machine called the “topografiner” that, like the STM, used electron tunneling and three-dimensional scanning to measure “the microtopography of metallic surfaces,” but used a field emitter instead of a tip to create tunneling conditions (Young, Ward, and Scire 999). The topografiner was not very successful in achieving measurements due to interference from outside vibrations, caused by people walking in the building, for example. In the early 1980s, STM inventors Gerd Binnig and Heinrich Rohrer, along with Christoph Gerber and Edmund Weibel, reduced outside vibrations enough to measure the tunneling and develop the STM (Binnig et al. 178–180).29 The story of how electron tunneling became a measurement technique illustrates the complex mediation required of some visualization technologies, mediation anchored in the practices of a larger community.
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