by Law Siu Wah = 超薄薄膜的應變和記憶效應 / 羅紹華. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Law Siu Wah = Chao bo bo mo de ying bian he ji yi xiao ying / Luo Shaohua. / Acknowledgement --- p.i / Abstract --- p.ii / 論文摘要 --- p.iv / Table of contents --- p.v / List of Figures --- p.viii / List of Tables --- p.xii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Magnetoresistance (MR) --- p.1 / Chapter 1.1.1 --- Colossal magnetoresistance (CMR) in rare-earth manganites --- p.2 / Chapter 1.1.2 --- Double exchange mechanism --- p.3 / Chapter 1.1.3 --- Jahn-Teller effect --- p.6 / Chapter 1.1.4 --- Tolerance factor --- p.8 / Chapter 1.1.5 --- The effect of doping --- p.10 / Chapter 1.2 --- Our motivation --- p.12 / Chapter 1.3 --- Scope of this thesis work --- p.12 / References --- p.14 / Chapter Chapter 2 --- Experimental methods / Chapter 2.1 --- Thin film deposition --- p.16 / Chapter 2.1.1 --- Facing Target Sputtering (FTS) --- p.16 / Chapter 2.1.2 --- Vacuum system --- p.19 / Chapter 2.2 --- Annealing systems --- p.20 / Chapter 2.2.1 --- Oxygen annealing system --- p.20 / Chapter 2.2.2 --- Vaccum annealing system --- p.21 / Chapter 2.3 --- Characterization --- p.22 / Chapter 2.3.1 --- Profilometer --- p.22 / Chapter 2.3.2 --- X-ray diiffraction (XRD) --- p.22 / Chapter 2.3.3 --- Resistance measurement --- p.24 / References --- p.25 / Chapter Chapter 3 --- Expitaxial growth of La0.67Ca0.33MnO3 single layer thin film / Chapter 3.1 --- Fabrication and characteristics of La0.67Ca0.33MnO3 target --- p.26 / Chapter 3.2 --- Substrate materials --- p.31 / Chapter 3.3 --- Epiaxial growth of LCMO thin film --- p.33 / Chapter 3.3.1 --- Deposition conditions --- p.33 / Chapter 3.3.2 --- Deposition procedure --- p.35 / Chapter 3.3.3 --- Oxygen annealing effect --- p.36 / References --- p.41 / Chapter Chapter 4 --- Strain effect in expitaxial growth of La0. 67Ca0 .33MnO3 thin films / Chapter 4.1 --- Introduction --- p.42 / Chapter 4.2 --- Preparation of LCMO ultra-thin film on different substrates --- p.45 / Chapter 4.2.1 --- Sample preparation --- p.45 / Chapter 4.2.2 --- Oxygen annealing treatment --- p.45 / Chapter 4.3 --- Resistance measurement --- p.50 / Chapter 4.3.1 --- Thickness effect --- p.50 / Chapter 4.3.2 --- Strain effect --- p.63 / Chapter 4.4 --- Discussions --- p.68 / References --- p.69 / Chapter Chapter 5 --- Memory effect and thermal effect of ultra-thin La0.67Ca0.33MnO3 films / Chapter 5.1 --- Introduction --- p.71 / Chapter 5.2 --- Sample description and measurement method --- p.72 / Chapter 5.3 --- Memory effect and thermal effect --- p.73 / Chapter 5.4 --- Discussion --- p.77 / References --- p.80 / Chapter Chapter 6 --- Conclusion / Chapter 6.1 --- Conclusion --- p.81 / Chapter 6.2 --- Future work --- p.82

Compared with traditional radioimmunoassay and fluoroimmunoassay for early diseases detection, the magnetic immunoassay utilizing magnetic nanoparticles as bio-labels and magnetic signal sensors as detectors has remarkable advantages because most biological samples exhibit no magnetic background and highly sensitive measurements can be performed. This thesis presents the development of biodetection platform taking advantage of the physical-and chemical-stability, low-toxicity, and environmentally-safety of magnetic iron oxide nanoparticles (IONPs) and the high-sensitivity, low-cost, and portable capabilities of magnetoresistive (MR) sensors. The first part explained why a magnetic biodetection platform is desirable, and what advantages it possesses. Then the magnetism of IONPs utilized in this detection system was introduced, followed by the introduction of main synthesis methods to obtain the desirable IONPs. The working principle of MR sensor was explained, and the recent advances about the biodetection platforms with various magnetoresistive sensors and magnetic IONPs labeling was reviewed. A brief summary of new contributions reported in this thesis was summarized. Then the establishment of home-made measurement setups for the characterization of MR sensor was described. The MR loops of MR sensors can be obtained with the instrument using two-point probe measurement, four-point probe measurement, or Wheatstone bridge measurement. The single MTJ sensor, MTJs array sensor, and the GMR spin valve sensor in Wheatstone bridge were characterized here. The magnetic IONPs were prepared through co-precipitation method and thermal decomposition method, and then surface-functionalized using citric acid and fatty acids to acquire carboxyl groups for the binding ability with biomolecules. The physical and chemical properties, sterilizing-treatment tolerability and biocompatibility of nanoparticles were studied. Furthermore, two new synthesis methods were developed to obtain novel magnetic gold/iron oxide nanocomposites for their potential use as magnetic bio-labels. A magnetic detection platform was built, and the detection of 10-nm superparamagnetic IONPs with MR sensor was first realized here. The output signal of the giant magnetoresistive (GMR) sensor in Wheatstone bridge exhibited log-linear function of the concentration of IONPs, making our sensing system suitable for use when ultra-small bio-labels are needed. The biodetection platform with MR sensor and IONPs was successfully developed and applied for the detection of antigen biomolecules. The feasibility of magnetic biodetection system, based on magnetic tunneling junction (MTJ) sensors and carboxyl-group functionalized IONPs, to detect AFP antigens (liver cancer biomarker) and p24 antigens (HIV biomarker) was demonstrated here for the first time. By taking advantages of its high sensitivity, low power consumption, low cost, and feasibility to be miniaturized, the development of magnetoresistive biodetection platform will bring revolutionary impact on the biodetection techniques for clinical early diseases diagnosis. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Thesis (M.S.)--Youngstown State University, 2008. / Includes bibliographical references (leaves 35-36). Also available via the World Wide Web in PDF format.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on June 11, 2009) Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 91-94). Available also in a digital version from Dissertation Abstracts.

In this work, nickel-gold multi-segmented magnetic nanowires were grown by electrodeposition in anodized alumina templates. The templates were fabricated by a two step anodization process of aluminum disks in an aqueous solution of oxalic acid. In this process, ordered pores grew in an alumina oxide layer at the exposed aluminum area. Each disk was electropolished before the anodization process and the features at its surface were characterized to assess the effect on the pore ordering. Nickel Watts and gold cyanide electrolyte baths were prepared to electrodeposit pure nickel and gold in the templates. Both solutions response to a range of externally applied voltages was characterized and a threshold voltage above which deposition occurs is reported. Single nanowires were isolated by chemically dissolving the template and dispersed in ethanol. Devices were fabricated with these isolated nanowires in which gold contacts were deposited to measure the resistance. A current pulse setup was implemented in a magnetoresistance system allowing to send current pulses with amplitude as low as 2nA and 50μs width. Magneto resistance measurement were carried out on the single nanowires devices and the effect of current pulses was studied. It was found that distinct resistance states can be achieved by applying a determined current pulse at a constant applied field and that the initial state can be recovered by removing excess charge from the nanowire. Finally, the effect of annealing the nanowires in an air atmosphere at 150°C for 24 hours is studied showing that the nickel sections oxidize and the gold sections remain unchanged.

No description available.

No description available.

published_or_final_version / Physics / Doctoral / Doctor of Philosophy