Structure And Magnetic Properties Of Acceptor Doping SnO₂ Diluted Magnetic Semiconductors

With the progress of era and the development of science and technology,people have entered into the information age.Information processing and storage are required simultaneously because of miniaturization and high storage density of device.The processing of information is attributed to the electronic charge properties,which is completed by semiconductor materials.However,the storage of information is attributed to electronic spin properties,which is accomplished by the magnetic materials.Among them,diluted magnetic semiconductors received great attention because it can process and storage information at the same time through taking advantage of the electronic charge and spin.SnO₂ is one type of wide bandgap transparent oxide semiconductors with excellent performance.However,SnO₂ is not research center in the past for a long time.As development of other oxide semiconductors?such as ZnO,In2O3,etc.?entered into the bottleneck,SnO₂ gradually become the mainstream of scientific research,is expected to become practically new type of electronic materials.Fe doped and N doped SnO₂ thin films were deposited on Si?100?substrate and ultra clear glass using radio frequency?RF?magnetron sputtering method in this paper.Structure characterization and performance testing method such as XRD,XPS and XAFS,SQUID,PL,UV,reveals the essence of magnetic and state the origin of eigen ferromagnetism of acceptor doped SnO₂ thin film.?1?Sn_1-xFe_xO₂?x=0,0.023,0.042 and 0.075?films.Fe doping do not alter the tetragonal rutile structure of SnO₂,with the increase of Fe concentration,crystal quality of films decline.Local structure of Fe was investigated using X-ray absorption fine structure?XAFS?,the results show that no Fe metal clusters or secondary phases are formed,the doped Fe atoms exist in the form of Fe2+/Fe3+ were entered into SnO₂ lattice and substitute the Sn sites,Fe 2p XPS spectra verify the existence of Fe2+/Fe3+.Feff 9.0 fitting results show that during the process of substitution,oxygen vacancies were formed to compensate charge nonequilibrium,asymmetric O 1s XPS spectra verify the existense of oxygen vacancies.All the films exhibit room temperature ferromagnetism,the saturation magnetization and Fe doping concentration has positive correlation.Fe doping concentration increases corresponding carrier concentration declined dramatically.When Fe doping concentration reach 7.5%,thin film samples show high insulation state,indicates the carrier concentration is very low,and negatively related to the saturation magnetization,exclude the possibility of carriers induced ferromagnetic.Bound magneto polaron induced by oxygen vacancy may play a crucial role detect for room temperature ferromagnetism.?2?SnO_2-xN_x?x=0,0.038,0.091,0.130?films.Under the condition of vacuum,SnO_2-xNx films were prepared through changing the flow-rate ratio of Ar/N2.Results show that samples keep the the tetragonal rutile structure along with the whole scope of N dopingconcentration.N 1s XPS spectra demonstrate that N atoms were existed in the form of N-3,no Sn-N bond were formed,O 1s XPS spectra verify the existence of oxygen vacancies in the crystal.As N doping concentration increase,the position of emission peak have no distinct displacement,but the ratio of oxygen vacancies increase obviously.The ultraviolet-visible photoluminescence peak origin from oxygen vacancy and the luminous intensity of ultraviolet-visible peak has a positive correlation on N doping concentration,which demonstrate the concentration of oxygen vacancy increase with the increase of N doping concentration.All the samples show semiconductor behaviors,we fitted through the combination of Mott variable range hopping behavior and Hard bandgap hopping behavior.The electronic conducting mechanism is dominated by Mott variable range hopping behavior at low temperature and Hard bandgap hopping behavior at high temperature,suggesting that the carriers are strongly located.All the samples exhibit intrinsic ferromagnetism at room temperature,and the saturation magnetization increase with the increase of N doping concentration.Bound magnetic polarons induced by oxygen vacancy may be the most reasonable mechanism to explain room-temperature ferromagnetism.