ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
Displaying 1 - 4 of 4
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- All Subjects: Physics
- Creators: Qing, Quan
Description
Single molecule identification is one essential application area of nanotechnology. The application areas including DNA sequencing, peptide sequencing, early disease detection and other industrial applications such as quantitative and quantitative analysis of impurities, etc. The recognition tunneling technique we have developed shows that after functionalization of the probe and substrate of a conventional Scanning Tunneling Microscope with recognition molecules ("tethered molecule-pair" configuration), analyte molecules trapped in the gap that is formed by probe and substrate will bond with the reagent molecules. The stochastic bond formation/breakage fluctuations give insight into the nature of the intermolecular bonding at a single molecule-pair level. The distinct time domain and frequency domain features of tunneling signals were extracted from raw signals of analytes such as amino acids and their enantiomers. The Support Vector Machine (a machine-learning method) was used to do classification and predication based on the signal features generated by analytes, giving over 90% accuracy of separation of up to seven analytes. This opens up a new interface between chemistry and electronics with immediate implications for rapid Peptide/DNA sequencing and molecule identification at single molecule level.
ContributorsZhao, Yanan, 1986- (Author) / Lindsay, Stuart (Thesis advisor) / Nemanich, Robert (Committee member) / Qing, Quan (Committee member) / Ros, Robert (Committee member) / Zhang, Peiming (Committee member) / Arizona State University (Publisher)
Created2014
Description
An electrical current with high spin polarization is desirable for the performance of novel spintronics devices, such as magnetic tunnel junction and giant magnetoresistance devices. The generation of spin polarized current can be from ferromagnetic materials or triplet superconductors.
Anomalous Hall effect (AHE) is an effective way to study the properties of magnetic structures. The scattering of electrons by the magnetic moments affects the change of resistance, which can be used to detect the magnetization. In this dissertation, AHE is used to study the perpendicular magnetic anisotropy (PMA) structures, including Co/Pt and Ta/CoFeB/MgO.
Domain walls exist in all ferromagnetic materials. This dissertation studies the domain wall movement in the Ta/CoFeB/MgO structure. A single domain is observed by measuring the anomalous Hall effect. On the other hand, a zero Hall step is successfully observed in a single layer of magnetic material for the first time, which can be used to fabricate advanced domain wall spintronics devices.
Besides the normal ferromagnetic material, the generation of spin polarized current in superconductor is also important for Spintronics. The electrons in superconductors form Cooper pairs. In this dissertation, Andreev Reflection Spectroscopy (ARS) is used to study the spin configuration in Cooper pairs.
Generally, ferromagnetism and superconductivity can not co-exist. In this dissertation, the Bi/Ni bilayer structure has been studied with ARS, and the measurement results show a triplet superconductivity below 4K. The appearance of superconductivity is believed to be attributed to the Bi-Ni interface, and the triplet Cooper pair makes it a promising candidate in superconducting spintronics.
Besides, a Bi3Ni single crystal is also studied with ARS. The measurements show a singlet superconductivity in this material, which further proves the importance of the Bi/Ni interface to achieve triplet superconductivity.
Finally, ARS is also used to study NbSe2 monolayer, a 2D superconductor. The monolayer is verified by the measurements of critical temperature and critical field, which are different from the values of multilayer or bulk. Andreev reflection results show that NbSe2 monolayer is a singlet superconductor and there is no node exist in the superconducting gap for a in plane magnetic field up to 58 kOe.
Anomalous Hall effect (AHE) is an effective way to study the properties of magnetic structures. The scattering of electrons by the magnetic moments affects the change of resistance, which can be used to detect the magnetization. In this dissertation, AHE is used to study the perpendicular magnetic anisotropy (PMA) structures, including Co/Pt and Ta/CoFeB/MgO.
Domain walls exist in all ferromagnetic materials. This dissertation studies the domain wall movement in the Ta/CoFeB/MgO structure. A single domain is observed by measuring the anomalous Hall effect. On the other hand, a zero Hall step is successfully observed in a single layer of magnetic material for the first time, which can be used to fabricate advanced domain wall spintronics devices.
Besides the normal ferromagnetic material, the generation of spin polarized current in superconductor is also important for Spintronics. The electrons in superconductors form Cooper pairs. In this dissertation, Andreev Reflection Spectroscopy (ARS) is used to study the spin configuration in Cooper pairs.
Generally, ferromagnetism and superconductivity can not co-exist. In this dissertation, the Bi/Ni bilayer structure has been studied with ARS, and the measurement results show a triplet superconductivity below 4K. The appearance of superconductivity is believed to be attributed to the Bi-Ni interface, and the triplet Cooper pair makes it a promising candidate in superconducting spintronics.
Besides, a Bi3Ni single crystal is also studied with ARS. The measurements show a singlet superconductivity in this material, which further proves the importance of the Bi/Ni interface to achieve triplet superconductivity.
Finally, ARS is also used to study NbSe2 monolayer, a 2D superconductor. The monolayer is verified by the measurements of critical temperature and critical field, which are different from the values of multilayer or bulk. Andreev reflection results show that NbSe2 monolayer is a singlet superconductor and there is no node exist in the superconducting gap for a in plane magnetic field up to 58 kOe.
ContributorsZhao, Gejian (Author) / Chen, Tingyong (Thesis advisor) / Bennett, Peter (Committee member) / Nemanich, Robert (Committee member) / Qing, Quan (Committee member) / Arizona State University (Publisher)
Created2018
Description
My research focuses on studying the interaction between spatiotemporally encoded electric field (EF) and living cells and biomolecules. In this thesis, I report two projects that I have been working on to address these questions. My first project studies the EF modulation of the extracellular-signal-regulated kinase (ERK) pathway. I demonstrated modulation of ERK activities using alternative current (AC) EFs in a new frequency range applied through high-k dielectric passivated microelectrodes with single-cell resolution without electrochemical process induced by the EF stimulation. Further experiments pinpointed a mechanism of phosphorylation site of epidermal growth factor (EGF) receptor to activate the EGFR-ERK pathway that is independent of EGF. AC EFs provide a new strategy to precisely control the dynamics of ERK activation, which may serve as a powerful platform for control of cell behaviors with implications in wide range of biomedical applications.
In the second project, I used solid-state nanopore system as the base platform for single molecule experiments, and developed a scalable bottom-up process to construct planar nanopore devices with self-aligned transverse tunneling junctions, all embedded on a nanofluidic chip, based on feedback-controlled reversible electrochemical deposition in a confined nanoscale space. I demonstrated the first simultaneous detection of translocating DNA molecules from both the ionic channel and the tunneling junction with very high yield. Meanwhile, the signal amplitudes from the tunneling junction are unexpectedly high, indicating that these signals are probably dominated by transient currents associated with the fast motion of charged molecules between the transverse electrodes. This new platform provides the flexibility and reproducibility required to study quantum-tunneling-based DNA detection and sequencing.
In summary, I have developed two platforms that engineer heterogenous EF at different length scales to modulate live cells and single biomolecules. My results suggest that the charges and dipoles of biomolecules can be electrostatically manipulated to regulate physiological responses and to push detection resolution to single molecule level. Nevertheless, there are still many interesting questions remain, such as the molecular mechanism of EF-protein interaction and tunneling signal extraction. These will be the topics for future investigations.
ContributorsWang, Yuan (Author) / Qing, Quan (Thesis advisor) / Lindsay, Stuart (Committee member) / Wang, Shaopeng (Committee member) / Ros, Robert (Committee member) / Arizona State University (Publisher)
Created2021
Description
Driven by the curiosity for the secret of life, the effort on sequencing of DNAs and other large biopolymers has never been respited. Advanced from recent sequencing techniques, nanotube and nanopore based sequencing has been attracting much attention. This thesis focuses on the study of first and crucial compartment of the third generation sequencing technique, the capture and translocation of biopolymers, and discuss the advantages and obstacles of two different nanofluidic pathways, nanotubes and nanopores for single molecule capturing and translocation. Carbon nanotubes with its constrained structure, the frictionless inner wall and strong electroosmotic flow, are promising materials for linearly threading DNA and other biopolymers for sequencing. Solid state nanopore on the other hand, is a robust chemical, thermal and mechanical stable nanofluidic device, which has a high capturing rate and, to some extent, good controllable threading ability for DNA and other biomolecules. These two different but similar nanofluidic pathways both provide a good preparation of analyte molecules for the sequencing purpose. In addition, more and more research interests have move onto peptide chains and protein sensing. For proteome is better and more direct indicators for human health, peptide chains and protein sensing have a much wider range of applications on bio-medicine, disease early diagnoses, and etc. A universal peptide chain nanopore sensing technique with universal chemical modification of peptides is discussed in this thesis as well, which unifies the nanopore capturing process for vast varieties of peptides. Obstacles of these nanofluidic pathways are also discussed. In the end of this thesis, a proposal of integration of solid state nanopore and fixed-gap recognition tunneling sequencing technique for a more accurate DNA and peptide readout is discussed, together with some early study work, which gives a new direction for nanopore based sequencing.
ContributorsSong, Weisi (Author) / Lindsay, Stuart (Thesis advisor) / Ros, Robert (Committee member) / Qing, Quan (Committee member) / Zhang, Peiming (Committee member) / Arizona State University (Publisher)
Created2015