Observing and Manipulating Single Electrons Confined to Silicon Dangling Bond Ensembles with Non-Contact Atomic Force Microscopy

• Author / Creator

  Vine, Wyatt

• Non-contact atomic force microscopy (nc-AFM) is capable of inducing and resolving single-electron charge transitions of surface adsorbates. Here, these techniques are extended by studying the charge configurations of dangling bond (DB) ensembles on the hydrogen-terminated silicon surface. nc-AFM is used to monitor the location of single electrons confined to DB ensembles that are created via scanning tunnelling microscopy hydrogen lithography. Electrons are found to remain strongly localized to individual DBs, but occasionally switch sites. The dominant behaviour of these meta-stable charge configurations is a result of the Coulombic interactions between the confined electrons and relaxation of the silicon lattice. The application of charge sensing nc-AFM techniques to the characterization of field-controlled computing devices is explored. At zero applied bias voltage it is found that the charge of individual DBs can be selectively manipulated by controlling the tip's position, resulting in the ability to prepare specific charge configurations of larger DB ensembles. The ability to manipulate the charge state of individual DBs is a direct result of the total tip induced band bending, which has two components at zero applied bias voltage: the contact potential difference between the tip and sample, and the image charge induced in the tip. At small tip-sample separations the image charge component can become dominant, preferentially stabilizing electrons in the dangling bonds beneath the tip. The tip's influence is further characterized by investigating how it can cause unintentional changes to the ensembles' charge configuration, and by looking for evidence of a 'sweet-spot,' where the tip interacts weakly with the charge configurations. In addition to the charge manipulation experiments, sub-surface defects are investigated with I(V ) spectroscopy. Notably, negative differential resistance is observed on DBs patterned directly over low-conductance defects, suggesting that the DB and defect may hybridize.

• Subjects / Keywords

  • Scanning Tunnelling Microscopy
  • Manipulation
  • Atomic Force Microscopy
  • Dangling Bond
  • Silicon

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3833NF1P

• License

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