D⁰Ferromagnetism, Optical And Electrical Properties Of In₂O₃-based Films

d0ferromagnetism, which describes a recently discovered physical phenomenonthat a nonmagnetic oxide semiconductor can be made to behave ferromagnetism,overturns a traditional impression that ferromagnetism only occurs in materials withpartially filled d or f shells. The discovery of d0ferromagnetism not only opens a newchanllange on the ferromagnetic origin, but also effectively rules out the probableimpact induced by the ferromagnetic secondary phases. Therefore, the study on d0materials is very significant for the ferromagnetic origin of magnetic semiconductorsand its applications in semiconductor devices.As a wide gap oxide semiconductor, In2O3has excellent properties in optics,electricity and gas-sensitivity. However, further applications of In2O3system arehindered by the difficulties in obtaining stable p-type conducting androom-temperature ferromagnetism. Therefore, the work focusing on the structural,ferromagnetic, optical and electrical properties of pure and N doped In2O3films aresystematically promoted. Following works are mainly carried out:1. Polycrystalline In2O3films oriented along (222) direction were prepared byradiofrequency magnetron sputtering. And the effect of growing atmosphere andvacuum-annealing on the properties of structure, optics, conductivity andferromagnetism were systematically studied. According to our results, a conversion ofconductivity from n-type to p-type was observed as the O2/Ar flux ratio reaches15:15,indicating the carrier type can be modulated by changing the O2/Ar flux ratio duringpreparation. Room temperature d0ferromagnetism was observed in pure In2O3films.The saturation magnetization changed non-monotonously as the O2/Ar flux ratioincreases, indicating a diverse origin of d0ferromagnetism in different conductingregions. Moreover, our results show that the ferromagnetism of In2O3films can beeffectively enhanced by vacuum-annealing. An enhanced saturation magnetizationfrom0.5to5.5emu/cm3was observed.2. N-In2O3films were prepared by magnetron sputtering and thermal oxidationof InN. The effect of growing atmosphere and annealing temperature or time on thestructure, band gap and ferromagnetism in N-In2O3system were studied. As for theN-In2O3films prepared by sputtering, the ferromagnetism increases monotonously asthe N2flux increases (bellow the solubility limitation), indicating the ferromagnetism can be effectively enhanced by N-doping. A maximum moment of3.5emu/cm3wasobtained as the N2/Ar flux ratio reaches10:20. Mainwhile, as the N2flux increases, agradually conversion of the structure from cubic bixbyite to wurtzite can be observedwith a monotonously changes of optical band gap from3.74to2.25eV. Therefore, theband gap can be modulated within a large range by N-doping. Moreover, theN-doping can also be realized to enhance the ferromagnetism of In2O3films byreasonably controling the temperature and time of oxidating InN. A maximummoment of4.5emu/cm3was observed by thermal oxidating InN films at500oC for2h.