Studies On The Magnetism Of Mn Doped Nano ZnO Dilute Magnetic Semiconductors

As the new basic materials of making spintronic devices and studying the spin ofelectrons, ZnO-based dilute magneic semiconductors （DMSs） have attracted a greatmany people who are interest in spintronics due to the observations offerromagnetism.Spintronics has paved the way to exploit spin in addition to charge insemiconductor devices. The main challenge for practical application of the DMSmaterials is the attainment of a Curie temperature at or preferably above roomtemperature to be compatible with junction temperatures. Among the studies oftransition-metal doped conventional III–V and II–VI semiconductors,transition-metal-doped ZnO and GaN became the most extensively studied topicalmaterials since the prediction by Dietl et al., based on mean field theory, as promisingcandidates to realize a diluted magnetic material with Curie temperature above roomtemperature. The underlying assumptions, however, such as transition metalconcentrations in excess of 5% and hole concentrations of about 10²⁰cm^-3, have notgotten as much attention. The particular predictions are predicated on the assumptionthat hole mediated exchange interaction is responsible for magnetic ordering. Amongthe additional advantages of ZnO- and GaN-based DMSs are that they can be readilyincorporated in the existing semiconductor heterostructure systems, where a numberof optical and electronic devices have been realized, thus allowing the exploration ofthe underlying physics and applications based on previously unavailable combinationsof quantum structures and magnetism in semiconductors.In this dissertation, spintronics and the study background of DMSs were simplypresented firstly, and we also reviewed the research situation of DMSs, especiallyZnO-based. Simutaneously, there are also some theory explainations on theferromagnetic mechanism of DMSs which are popular in present, such as RKKYtheory, double change theory and bound magnetic polaron （BMP） theory.In chapter 2, we introduced the various basic properties of ZnO, and also withcrystal structure and defects in ZnO. In addition, some simple sample preparationmethod of ZnO nano materials such as sol-gel, hydrogenthemal, co-precipitationmethod, along with the characterization and maesurement method such as XRD, TEM,PL spectrum and VSM.The chapter 3 and 4, we discussed the effects of Mn concetration and oxygen vacancies defects on the magnetism in ZnO. Based on the observation in ourexperiments, we also gave some analysis and explanations on the magnetismmechanism.