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Atomic Electronics With Silicon Dangling Bonds: Error Correction, Logical Gates, and Electrostatic Environment
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- Author / Creator
- Huff, Taleana
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With the potential to unleash a new basis for electronics that are more energy efficient, faster, and at the ultimate scale in size density, single atoms as building blocks for miniature circuity have long been a technological holy grail. Preventing significant development have been various roadblocks such as practical operation temperatures, limited error correction ability, lack of homogeneity of device properties, and the ability of atomic patterns to be electrically isolated from the substrate they are put on. Here, we solve these issues and put forth a platform based on the atomically precise patterning of dangling bonds on a hydrogen-terminated silicon substrate. These dangling bonds exhibit electronic band gap states that allow them to fundamentally act as atomically-sized quantum dots, with their gap nature substantially electrically isolating them from mixing with bulk properties. They are structurally stable up to room temperature, with strong evidence supporting their function as binary logic elements at these temperatures too, unlike prior atomic logic approaches. In this work we present three key advancements for this emerging technology. The first is a reliable method of error correction for dangling bond structures. While great strides have been made over the last decade to improve fabrication of dangling bond arrays through the atomically-precise removal of surface hydrogen atoms, a complimentary way to correct errantly patterned ones was lacking. We demonstrate a methodology wherein a scanning probe tip is reliably functionalized with a single hydrogen atom at the apex, which can then be brought into spatial proximity of a dangling bond. At a key distance, a silicon-hydrogen covalent bond is induced mechanically, erasing the dangling bond with no damage to tip or sample. This erasure technique enabled the second important advancement of construction and actuation of binary atomic logic elements made of dangling bonds. In these demonstrations, paired dangling bonds (two) are occupied by one moveable electron to form a binary electronic building block. Clever geometric arrangement of many of these blocks, combined with control over the spatial arrangement of electrons within using local electrostatic fields, allowed for demonstration of low-power binary operation of a wire and logical OR gate at the atomic scale. Finally, the third key advancement, as a prerequisite for unimpaired operation of atomic binary circuitry, involved examination of the electrostatic landscape of the surface through development of a new technique employing a dangling bond as a moveable electrostatic point-probe. Irregularities in the local electrostatic environment on length scales comparable to our device sizes are looked for, which could impact their correct operation. Additionally, model fits on the dangling bond point-probe acquired data allowed extraction of important surface parameters, such as the dielectric constant and screening length, giving a basis to explore tolerance ranges for atomic-logic operation. For all presented experiments, the powerful single-electron sensitivity of non-contact atomic force microscopy (AFM) is employed, with the ensembles examined using a variety of AFM spectroscopic techniques. With these results combined together, we put forward dangling bonds on hydrogen-terminated silicon as an attractive medium for atomic electronics, with higher functionality immediately within reach.
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- Graduation date
- Spring 2020
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.