Zinc Oxide based Diluted Magnetic Semiconductors

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dc.contributor.advisor Prof.Nadia.A.Elmasry, Committee Member en_US
dc.contributor.advisor Prof.Jagdish Narayan, Committee Chair en_US
dc.contributor.advisor Prof.John.F.Muth, Committee Member en_US
dc.contributor.advisor Prof.John.T.Prater, Committee Member en_US
dc.contributor.author Ramahandran, Shivaraman en_US
dc.date.accessioned 2010-04-02T18:25:50Z
dc.date.available 2010-04-02T18:25:50Z
dc.date.issued 2007-12-15 en_US
dc.identifier.other etd-12022006-125127 en_US
dc.identifier.uri http://www.lib.ncsu.edu/resolver/1840.16/3015
dc.description.abstract During my graduate research I have synthesized materials known as diluted magnetic semiconductors (DMS) as epitaxial thin film structures using the process of pulsed laser deposition (PLD). These materials are envisioned to be of importance in the emerging field of spintronics where the charge as well as the spin of the charge carriers can be combined to yield unique functionalities to yield novel devices including, on-chip memories, ultra-low power devices etc. The material of interest in this dissertation was zinc oxide, a wide bandgap optoelectronic semiconductor. ZnO has a bandgap of 3.3 eV. It is an ideal candidate for spintronics applications, because Zn is the last of the first row transition metals, which leads to pretty high solubility of transition metals such as Co, Mn and V in ZnO. In a diluted magnetic semiconductor a fraction of the host atoms is substituted by the transition metal dopant ion. We have found that we can synthesize very high quality, single phase and single crystalline Zn(TM)O thin films on basal plane sapphire single crystals (-Al2O3). We have analyzed the magnetic properties of the three systems of ZnVO, ZnCoO and ZnMnO and found that ZnCoO and ZnMnO exhibit ferromagnetic ordering up to room temperature, when synthesized under high vacuum. In these conditions, the samples have a reasonable concentration of point defects which drive ZnO to n-type conductivity. By a combination of insitu and exsitu variation of parameters we have been able to tune the electronic and magnetic properties of these systems. From these studies we conclude that the main mechanism of magnetic ordering in these DMS materials is through a combination of defect related carrier induced exchange and bound magnetic polaron exchange. Device structures were fabricated using the as deposited samples to study the possibility of spin injection through semiconductors. We have observed that at low temperatures we see a considerable effect from this phenomenon in a magnetic tunnel junction kind of configuration. Hence, this study opens up new avenues and possibilities for a variety of spintronics applications. en_US
dc.rights I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dis sertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. en_US
dc.subject optoelectronics en_US
dc.subject spintronics en_US
dc.subject magneto-transport en_US
dc.subject thin films en_US
dc.subject magnetic en_US
dc.subject Diluted magnetic semiconductors en_US
dc.subject epitaxy en_US
dc.subject transmission electron microscopy en_US
dc.subject tunnel junction en_US
dc.subject magneto-resistance en_US
dc.subject spin injection en_US
dc.title Zinc Oxide based Diluted Magnetic Semiconductors en_US
dc.degree.name PhD en_US
dc.degree.level dissertation en_US
dc.degree.discipline Materials Science and Engineering en_US

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