Silicon Dangling Bonds Non-equilibrium Dynamics and Applications

• Author / Creator

  Taucer, Marco

• Dangling Bonds (DBs) on the silicon surface exist when a silicon atom lacks a bonding partner, resulting in a localized orbital which is not involved in any chemical bonds. On the hydrogen-terminated Si(100) surface, such DBs introduce a mid-gap state. DBs can be created on this surface by the selective desorption of a surface hydrogen atom using a Scanning Tunneling Microscope (STM). This thesis deals with characterization and fabrication of DBs in STM, as well as some of their potential applications. We discuss the unusual appearance of the silicon DB in STM, which can be understood in detail by considering the non-equilibrium charging effects that take place during imaging. We also show that the single-electron tunneling events that lead to non-equilibrium charging of the DB are directly observable in STM experiments. The tip-sample tunnel junction serves as a single electron-sensitive charge sensor, which measures the fluctuating charge of a single silicon DB as electrons tunnel on and off of the DB. Corresponding single-electron transfer rates are extracted, and these agree with the previously proposed model of non-equilibrium charging. Progress in DB fabrication is also discussed. Image analysis and desorption algorithms permit creation of DBs at pre-determined locations, leading to the creation of DB patterns of various sizes, from several DBs to thousands. Finally, a potential application of DBs, Quantum-dot Cellular Automata (QCA), is discussed. QCA is an emerging technology which promises tremendous advantages over today's Complementary Metal-Oxide-Semiconductor (CMOS) technology, if it can be realized at the atomic or molecular scale. Silicon DBs are a promising platform for QCA devices. Here, we focus on the issue of quantum correlations in QCA circuits, an issue which has not been important in prototype QCA demonstrations, but which may play an increasingly central role as QCA is brought to the atomic scale. Through computational simulations, we find that the inclusion of intercellular correlations qualitatively alters the ground state and thermal steady state of the QCA circuit.

• Subjects / Keywords

  • Nanotechnology
  • Silicon
  • Dangling Bond
  • QCA
  • STM
  • Cellular Automata

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R33B5WG81

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.