Coherence of Coupled Dangling-Bond Pairs on the Silicon Surface
| atmire.migration.oldid | 2122 | |
| dc.contributor.advisor | Sanders, Dr. Barry C. | |
| dc.contributor.advisor | DiLabio, Dr. Gino A. | |
| dc.contributor.author | Shaterzadeh-Yazdi, Zahra | |
| dc.date.accessioned | 2014-05-05T20:07:32Z | |
| dc.date.available | 2014-06-16T07:00:39Z | |
| dc.date.issued | 2014-05-05 | |
| dc.date.submitted | 2014 | en |
| dc.description.abstract | We characterize coherent dynamics of closely-spaced dangling bond (DB) pairs positioned on a silicon surface and sharing an excess electron. We investigate whether a coupled-DB pair is a potential candidate for a charge qubit. A dangling bond is an atomic-scale entity that acts like a quantum dot. By shrinking the scale of the quantum dots and the spacing between them, we expect that the excess-electron tunneling rate increases dramatically with decreasing inter-dot separation, while decoherence scales weakly. Our analysis of the coherent dynamics of coupled-DB pairs shows promise in this respect. The extremely high tunneling rate of the DB excess charge greatly exceeds the expected decoherence rates for a silicon-based system, thereby overcoming the critical obstacle of charge qubits for quantum computing purposes. However, this scaling advantage comes at the price of requiring rapid control and readout. We devise a scheme for measuring the DB-pair dynamics, but investigating the fast control is beyond the scope of this thesis. Furthermore, we investigate the effect of the silicon-surface structure on the coherence of a coupled-DB pair. The silicon surface of interest is well patterned, but it has an anisotropic structure. Therefore, the coupling strength of a DB pair depends on the arrangement of the DBs on the silicon surface. We employ ab initio techniques and calculate the energy splitting for a wide variety of coupled DB-pair configurations on this surface. The results show that the energy splitting (and consequently the tunneling rate of the DB-pair excess charge) is a function of the DBs’ location on the surface and also it strongly depends on the structural orientation of the DBs’ orbital. Based on the results, DB-pair configurations are categorized into four groups, such that the changing rate of energy splitting versus DB-pair separation is different among the groups. Knowing about the effect of the surface structure on the DB-pair energy splitting is especially useful when dealing with more complex systems such as DB subnanowires, quantum cellular automata cells, and quantum computing schemes. Also, the results help to have a better understanding of the coherence and bonding on this Si surface. As mentioned earlier, the highly coherent dynamics of coupled-DB pairs comes at the price of being too fast to be directly measured by any conventional technique. We therefore devise a scheme to characterize tunneling of the DB excess charge by measuring the time-averaged charge distribution of the DB pair with an atomic force microscope. In our approach, a DB pair is capacitively coupled to an atomic force microscope tip in the presence of an electrostatic potential bias applied along the DB pair, and a tunable mid-infrared laser to drive the pair. With a non-resonant laser field, the time-averaged charge distribution in the dangling-bond pair is asymmetric as imposed by the bias. However, as the laser becomes resonant with the coherent electron tunneling in the biased pair the theory predicts that the time-averaged charge distribution becomes symmetric. This resonant symmetry effect should not only reveal the tunneling rate, but also the nature and rate of decoherence of single-electron dynamics in our system. | en_US |
| dc.identifier.citation | Shaterzadeh-Yazdi, Z. (2014). Coherence of Coupled Dangling-Bond Pairs on the Silicon Surface (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/25349 | en_US |
| dc.identifier.doi | http://dx.doi.org/10.11575/PRISM/25349 | |
| dc.identifier.uri | http://hdl.handle.net/11023/1509 | |
| dc.language.iso | eng | |
| dc.publisher.faculty | Graduate Studies | |
| dc.publisher.institution | University of Calgary | en |
| dc.publisher.place | Calgary | en |
| dc.rights | University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission. | |
| dc.subject | Physics | |
| dc.subject.classification | Physics | en_US |
| dc.subject.classification | Condensed Matter | en_US |
| dc.subject.classification | Theory | en_US |
| dc.title | Coherence of Coupled Dangling-Bond Pairs on the Silicon Surface | |
| dc.type | doctoral thesis | |
| thesis.degree.discipline | Physics and Astronomy | |
| thesis.degree.grantor | University of Calgary | |
| thesis.degree.name | Doctor of Philosophy (PhD) | |
| ucalgary.item.requestcopy | true |