Some of the material in is restricted to members of the community. By logging in, you may be able to gain additional access to certain collections or items. If you have questions about access or logging in, please use the form on the Contact Page.
This dissertation presents work on improving the sensitivity of Hall magnetometry for single magnetic nanoparticle measurement by miniaturizing the devices down to submicron range. Limiting factors for Hall device performance, including noise and mesoscopic effects, will be explored. The first systematic low-frequency Hall noise measurements on submicron GaAs/AlGaAs 2DEG devices have been carried out at temperatures between 1.5K and 75K in order to understand the microscopic origin of 1/f noise in the Hall signals and to improve device performance. A surprisingly large gating effect was found, which suppresses the 1/f noise level up to several orders of magnitude with application of a modest gate voltage. Detailed temperature and gate voltage dependences of the noise spectra have been analyzed, and the data suggest that the noise originates predominantly from impurity switching processes and their dynamics in the selectively doped AlGaAs layer. This remote origin of the noise is further supported by the fact that the noise is almost independent of electron temperature but varies strongly with lattice temperature. A crossover from thermal activation to quantum tunneling was observed at T
A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
Includes bibliographical references.
Stephan von Moln´ar, Professor Co-Directing Dissertation; Peng Xiong, Professor Co-Directing Dissertation; Joe Schlenoﬀ, Outside Committee Member; Susan Blessing, Committee Member; Zachary Fisk, Committee Member; Pedro Schlottmann, Committee Member.
Florida State University
Use and Reproduction
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them.