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Spirals Growth of Topological Insulators Lian Li, University of Wisconsin-Milwaukee, DMR 1105839

Spirals Growth of Topological Insulators Lian Li, University of Wisconsin-Milwaukee, DMR 1105839.

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Spirals Growth of Topological Insulators Lian Li, University of Wisconsin-Milwaukee, DMR 1105839

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  1. Spirals Growth of Topological InsulatorsLian Li, University of Wisconsin-Milwaukee, DMR 1105839 During epitaxial growth of topological insulators such as Bi2Se3, spirals are observed regardless of substrates used. In this work, we discovered a novel mechanism that explains this universal behavior. Using scanning tunneling spectroscopy, we verified the linear dispersion of the Dirac states for films thicker than 6 quintuple layers (QLs), consistent with our DFT calculations. We further confirmed that the one-dimensional modes associated with dislocations are indeed prohibited in strong topological insulator Bi2Se3. Left panel: an STM image of growth spirals presented in 3D (100x100 nm2). Top right panel: calculated band structure for 8 QL Bi2Se3 film by density functional theory (DFT). Bottom right panel: tunneling spectrum where Dirac point ED marksthe conductance minimum, in excellent agreement with the calculations. Y. Liu, M. Weinert, and L. Li, Physical Review Letters 108, 115501 (2012).

  2. RET: Writing a Graphite Variable ResistorLian Li, University of Wisconsin-Milwaukee, DMR 1105839 Research experience for teachers (RET) Since 2005, the PI has been actively working with Physics teachers from Milwaukee Public Schools. This summer, Dave Verne, a science teacher from Case High School in Racine, spent eight weeks in PI’s lab, first learning properties of different types of carbon materials such as graphite,graphene, and buckyballs. He then constructed a “CD circuit” to demonstrate the concept of variable resistance. Dave will bring this knowledge to life in his high school classroom by presenting two projects: “Search for graphene” and “Circuits”. During the RET project, Dave constructed a variable resistor on a CD disc by connecting two Cu electrodes with a battery and a light emitting diode (LED). In the picture, Dave is completing the circuit by scribing a pencil between the Cu leads. The LED is turned on once the transferred graphite pieces complete the circuit. The light emission dims as the graphite layers are erased, demonstrating the concept of variable resistance.

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