Research Of Structure And Magnetism For Cr Doped ZnO-based Diluted Magnetic Semiconductors

Diluted magnetic semiconductors(DMS),which integrate the magnetism and semiconducting properties,are very significant from the view of both basic research and device application.So far,research on diluted magnetic semiconductor is one of the hot topics in the world.DMS could be used to construct magnetic and electronic device that utilize simultaneously the spin and charge degrees of freedom of carrier.Recent research on ferromagnetic semiconductors,high-efficiency spin injection,and spin manipulation and transport in semiconductors has attracted considerable interest in the past few years.DMS exhibit strong spin-dependent optical and transport properties,and these effects provide a physical basis for semiconductor spintronics devices.In this thesis,magnetic transition metallic elements Cr were introduced into ZnO by the radio frequency magnetron sputtering method;the magnetization behaviors and the origin of ferromagnetism of Zn_1-xCr_xO samples were studied.In the beginning the study background and application perspectives of DMS are introduced.Some of basic properties of DMS and ZnO,such as lattice structure,magnetic effect are also reviewed.Then the origin of ferromagnetism,the preparation process and the possible magnetic interactions of the Zn_1-xCr_xO samples have been introduced,especially the radio frequency magnetron sputtering method.In the end,the structure and magnetization behaviors of Zn_1-xCr_xO samples have been experimentally investigated.Based on the XRD,it is suggested that all sample's crystal structure is Wurtzite under low doped concentration,and the secondary phase is not found under the sensitivity of our apparatus.SEM shows that the films have leveled up surface.We compared the samples in different dopedions concentration,different underlay-temperature and different type of underlays that affect magnetism of DMS.So far,it is reported that many DMS film samples not only Curie temperature are low,but also its reproducibility is not high.The radio frequency magnetron sputtering is a good method for preparing diluted magnetic semiconductor,the Zn_1-xCr_xO samples which we prepare have room-temperature ferromagnetic ordering.Diluted magnetic semiconductors could be used to construct magnetic and electronic device that utilize simultaneously the spin and charge degrees of freedom of carrier.So,recent research on Zn-based ferromagnetic semiconductors will stimulate the development of spintronics.