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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- Creators: Zhao, Yuji
Description
Zinc telluride (ZnTe) is an attractive II-VI compound semiconductor with a direct
bandgap of 2.26 eV that is used in many applications in optoelectronic devices. Compared
to the two dimensional (2D) thin-film semiconductors, one-dimensional (1D)
nanowires can have different electronic properties for potential novel applications.
In this work, we present the study of ZnTe nanowires (NWs) that are synthesized
through a simple vapor-liquid-solid (VLS) method. By controlling the presence or
the absence of Au catalysts and controlling the growth parameters such as growth
temperature, various growth morphologies of ZnTe, such as thin films and nanowires
can be obtained. The characterization of the ZnTe nanostructures and films was
performed using scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy
(EDX), high- resolution transmission electron microscope (HRTEM), X-ray
diffraction (XRD), photoluminescence (PL), Raman spectroscopy and light scattering
measurement. After confirming the crystal purity of ZnTe, two-terminal diodes and
three-terminal transistors were fabricated with both nanowire and planar nano-sheet
configurations, in order to correlate the nanostructure geometry to device performance
including field effect mobility, Schottky barrier characteristics, and turn-on
characteristics. Additionally, optoelectronic properties such as photoconductive gain
and responsivity were compared against morphology. Finally, ZnTe was explored in
conjunction with ZnO in order to form type-II band alignment in a core-shell nanostructure.
Various characterization techniques including scanning electron microscopy,
energy-dispersive X-ray spectroscopy , x-ray diffraction, Raman spectroscopy, UV-vis
reflectance spectra and photoluminescence were used to investigate the modification
of ZnO/ZnTe core/shell structure properties. In PL spectra, the eliminated PL intensity
of ZnO wires is primarily attributed to the efficient charge transfer process
occurring between ZnO and ZnTe, due to the band alignment in the core/shell structure. Moreover, the result of UV-vis reflectance spectra corresponds to the band
gap energy of ZnO and ZnTe, respectively, which confirm that the sample consists of
ZnO/ZnTe core/shell structure of good quality.
bandgap of 2.26 eV that is used in many applications in optoelectronic devices. Compared
to the two dimensional (2D) thin-film semiconductors, one-dimensional (1D)
nanowires can have different electronic properties for potential novel applications.
In this work, we present the study of ZnTe nanowires (NWs) that are synthesized
through a simple vapor-liquid-solid (VLS) method. By controlling the presence or
the absence of Au catalysts and controlling the growth parameters such as growth
temperature, various growth morphologies of ZnTe, such as thin films and nanowires
can be obtained. The characterization of the ZnTe nanostructures and films was
performed using scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy
(EDX), high- resolution transmission electron microscope (HRTEM), X-ray
diffraction (XRD), photoluminescence (PL), Raman spectroscopy and light scattering
measurement. After confirming the crystal purity of ZnTe, two-terminal diodes and
three-terminal transistors were fabricated with both nanowire and planar nano-sheet
configurations, in order to correlate the nanostructure geometry to device performance
including field effect mobility, Schottky barrier characteristics, and turn-on
characteristics. Additionally, optoelectronic properties such as photoconductive gain
and responsivity were compared against morphology. Finally, ZnTe was explored in
conjunction with ZnO in order to form type-II band alignment in a core-shell nanostructure.
Various characterization techniques including scanning electron microscopy,
energy-dispersive X-ray spectroscopy , x-ray diffraction, Raman spectroscopy, UV-vis
reflectance spectra and photoluminescence were used to investigate the modification
of ZnO/ZnTe core/shell structure properties. In PL spectra, the eliminated PL intensity
of ZnO wires is primarily attributed to the efficient charge transfer process
occurring between ZnO and ZnTe, due to the band alignment in the core/shell structure. Moreover, the result of UV-vis reflectance spectra corresponds to the band
gap energy of ZnO and ZnTe, respectively, which confirm that the sample consists of
ZnO/ZnTe core/shell structure of good quality.
ContributorsPeng, Jhih-hong (Author) / Yu, Hongbin (Thesis advisor) / Roedel, Ronald (Committee member) / Goryll, Michael (Committee member) / Zhao, Yuji (Committee member) / Arizona State University (Publisher)
Created2017
Description
The development of biosensing platforms not only has an immediate lifesaving effect but also has a significant socio-economic impact. In this dissertation, three very important biomarkers with immense importance were chosen for further investigation, reducing the technological gap and improving their sensing platform.Firstly, gold nanoparticles (AuNP) aggregation and sedimentation-based assays were developed for the sensitive, specific, and rapid detection of Ebola virus secreted glycoprotein (sGP)and severe acute respiratory syndrome coronavirus 2 (SARS-COV2) receptor-binding domain (RBD) antigens. An extensive study was done to develop a complete assay workflow from critical nanobody generation to optimization of AuNP size for rapid detection. A rapid portable electronic reader costing (<$5, <100 cm3), and digital data output was developed. Together with the developed workflow, this portable electronic reader showed a high sensitivity (limit of detection of ~10 pg/mL, or 0.13 pM for sGP and ~40 pg/mL, or ~1.3 pM for RBD in diluted human serum), a high specificity, a large dynamic range (~7 logs), and accelerated readout within minutes. Secondly, A general framework was established for small molecule detection using plasmonic metal nanoparticles through wide-ranging investigation and optimization of assay parameters with demonstrated detection of Cannabidiol (CBD). An unfiltered assay suitable for personalized dosage monitoring was developed and demonstrated. A portable electronic reader demonstrated optoelectronic detection of CBD with a limit of detection (LOD) of <100 pM in urine and saliva, a large dynamic range (5 logs), and a high specificity that differentiates closely related Tetrahydrocannabinol (THC). Finally, with careful biomolecular design and expansion of the portable reader to a dual-wavelength detector the classification of antibodies based on their affinity to SARS-COV2 RBD and their ability to neutralize the RBD from binding to the human Angiotensin-Converting Enzyme 2 (ACE2) was demonstrated with the capability to detect antibody concentration as low as 1 pM and observed neutralization starting as low as 10 pM with different viral load and variant. This portable, low-cost, and versatile readout system holds great promise for rapid, digital, and portable data collection in the field of biosensing.
ContributorsIkbal, Md Ashif (Author) / Wang, Chao (Thesis advisor) / Goryll, Michael (Committee member) / Zhao, Yuji (Committee member) / Wang, Shaopeng (Committee member) / Arizona State University (Publisher)
Created2022
Description
The emergence of perovskite and practical efficiency limit to silicon solar cells has opened door for perovskite and silicon based tandems with the possibility to achieve >30% efficiency. However, there are material and optical challenges that have to be overcome for the success of these tandems. In this work the aim is to understand and improve the light management issues in silicon and perovskite based tandems through comprehensive optical modeling and simulation of current state of the art tandems and by characterizing the optical properties of new top and bottom cell materials. Moreover, to propose practical solutions to mitigate some of the optical losses.
Highest efficiency single-junction silicon and bottom silicon sub-cell in silicon based tandems employ monocrystalline silicon wafer textured with random pyramids. Therefore, the light trapping performance of random pyramids in silicon solar cells is established. An accurate three-dimensional height map of random pyramids is captured and ray-traced to record the angular distribution of light inside the wafer which shows random pyramids trap light as well as Lambertian scatterer.
Second, the problem of front-surface reflectance common to all modules, planar solar cells and to silicon and perovskite based tandems is dealt. A nano-imprint lithography procedure is developed to fabricate polydimethylsiloxane (PDMS) scattering layer carrying random pyramids that effectively reduces the reflectance. Results show it increased the efficiency of planar semi-transparent perovskite solar cell by 10.6% relative.
Next a detailed assessment of light-management in practical two-terminal perovskite/silicon and perovskite/perovskite tandems is performed to quantify reflectance, parasitic and light-trapping losses. For this first a methodology based on spectroscopic ellipsometry is developed to characterize new absorber materials employed in tandems. Characterized materials include wide-bandgap (CH3NH3I3, CsyFA1-yPb(BrxI1-x)3) and low-bandgap (Cs0.05FA0.5MA0.45(Pb0.5Sn0.5)I3) perovskites and wide-bandgap CdTe alloys (CdZnSeTe). Using this information rigorous optical modeling of two-terminal perovskite/silicon and perovskite/perovskite tandems with varying light management schemes is performed. Thus providing a guideline for further development.
Highest efficiency single-junction silicon and bottom silicon sub-cell in silicon based tandems employ monocrystalline silicon wafer textured with random pyramids. Therefore, the light trapping performance of random pyramids in silicon solar cells is established. An accurate three-dimensional height map of random pyramids is captured and ray-traced to record the angular distribution of light inside the wafer which shows random pyramids trap light as well as Lambertian scatterer.
Second, the problem of front-surface reflectance common to all modules, planar solar cells and to silicon and perovskite based tandems is dealt. A nano-imprint lithography procedure is developed to fabricate polydimethylsiloxane (PDMS) scattering layer carrying random pyramids that effectively reduces the reflectance. Results show it increased the efficiency of planar semi-transparent perovskite solar cell by 10.6% relative.
Next a detailed assessment of light-management in practical two-terminal perovskite/silicon and perovskite/perovskite tandems is performed to quantify reflectance, parasitic and light-trapping losses. For this first a methodology based on spectroscopic ellipsometry is developed to characterize new absorber materials employed in tandems. Characterized materials include wide-bandgap (CH3NH3I3, CsyFA1-yPb(BrxI1-x)3) and low-bandgap (Cs0.05FA0.5MA0.45(Pb0.5Sn0.5)I3) perovskites and wide-bandgap CdTe alloys (CdZnSeTe). Using this information rigorous optical modeling of two-terminal perovskite/silicon and perovskite/perovskite tandems with varying light management schemes is performed. Thus providing a guideline for further development.
ContributorsManzoor, Salman (Author) / Holman, Zachary C (Thesis advisor) / King, Richard (Committee member) / Goryll, Michael (Committee member) / Zhao, Yuji (Committee member) / Arizona State University (Publisher)
Created2019
Description
Design and development of optical sensors for the detection of specific targets, e.g., ions, molecules, proteins, light polarizations, is one of the most essential research topics in the field of nanophotonics that paves the way for significant technological progressions in chemical and biomarker detections, polarimetric imaging and other sensing related applications. In this dissertation, three designs of optical sensors based on plasmonic and dielectric nanostructures are thoroughly studied for the applications in chemicals, biomarkers and light polarization detection. Firstly, a plasmonic nanoantenna structure, which is composed of complementary anisotropic nanobars and nanoapertures featuring strong localized electric field enhancement at nanogap region, demonstrates both high sensitivity refractometric detection and specific infrared fingerprint detection for chemical sensing. Specifically, the sensor can probe monolayer thin octadecanethiol with a large resonance shift of 136 nm and all four characteristic infrared fingerprints detected. Secondly, a bio-inspired double-layered metasurface structure, which is made of dielectric nanoantenna and plasmonic nanogratings, mediates strong optical chirality and enables the selection of circularly polarized light handedness (extinction ratio ≥ 35) with high transmission efficiency (≥ 80%). The structure can be further integrated on-chip with linear polarizers for highly precise full-Stokes polarimetric detection with minimum transmission loss. Lastly, a gold nanoparticle based colorimetric assay is designed for high sensitivity, specificity and rapid detection of infectious diseases related biomarkers. The complete design workflows from critical reagents productions, rapid detection protocol to assay characterizations are extensively studied. Detection of Ebola virus disease biomarker, secreted glycoprotein, within 20 minutes are experimentally demonstrated with limit of detection down to ~40 pM and a broad detection range from 10 pM to 1 µM.
The designs of the three sensors propose novel and versatile design concepts for the development of sensing devices in the detection of chemicals, biomarkers and light polarization. The efforts in the fundamental theoretical analysis and experimental demonstrations are expected to provide valuable contents to the optical sensor researches and to potentially inspire new sensor designs for broad sensing applications in the future.
ContributorsChen, Xiahui (Author) / Wang, Chao (Thesis advisor) / Zhao, Yuji (Committee member) / Wang, Liping (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2021