Study On Properties Of Zno:Mn Thin Film Implanted With Nitrogen Ions

Recently, because of its advantageous physical properties-direct wide band gap(3.37eV) and large free exaction binding energy of60meV in room temperature, peoplehas been interest in zinc oxide (ZnO) for its potential applications in optoelectronic field,such as ultraviolet light-emitting diodes (LED) and laser diodes (LD), piezoelectricdevice, solar battery and so on. And ZnO diluted magnetic semiconductor (DMS) withroom-temperature ferromagnetism which involving charge and spin degrees of freedomof electrons in a single substance are used to realize high-performance, super-fast andlow power consumption spintronic devices. Theoretical studies suggest thatroom-temperature ferromagnetism might be in p-type ZnO:Mn. Among possibleacceptor dopants, nitrogen is a good candidate for making p-type ZnO because of itssmall size and the small ionization energy. However, the reported experimental resultsin ferromagnetism of (Mn,N)-codoped ZnO suggest that the electrical properties,structure, magnetic and its origin often exist certain controversy susceptible to the Nsource, doping methods, and other factors. In addition, the room-temperatureferromagnetism has also been observed in n-type ZnO system and pristine ZnO withlow dimensionality, and it originate from the electron and defects such as oxygenvacancies or zinc interstitial. In all, it is necessary to study the magnetism and its originfor Mn doped ZnO films.In this paper, ZnO:Mn thin films deposited on quartz glass substrates at varioustemperatures were fabricated by radio frequency (RF) magnetron sputtering technique.The influences of substrate temperature on the structural, optical and electricalproperties were investigated by x-ray diffraction, scanning electron micrograph,transmission spectrum, fluorescence spectrum and Hall measurement system. Theresults indicate that the crystallization quality, surface morphology and the near bandedge emission (NBE) of the samples can be improved with increasing the substratetemperature. Moreover, it is also observed that the higher substrate temperate isfavorable for suppression of zinc interstitial (Zni) and Zni-related defects, which hascorrelations with the electrical characteristics of the ZnO:Mn films. Then the Mn-N codoped ZnO thin films have been fabricated usingradio-frequency magnetron sputtering technique in optimum technology together withthe direct N+ion-implantation and the effects of annealing temperature onmicrostructure optical and room-temperature ferromagnetism of the thin films wasinvestigated. The results indicate that both divalent Mn2+and trivalent N3-ions areincorporated into ZnO lattice. As the annealing temperature increased, the latticedistortion induced by N+ion-implantation could decrease, and the N3-may escape fromthe films in the form of N2which result in the reducing of acceptor (NO) concentration.Ferromagnetism was observed in the (Mn,N)-codoped ZnO thin films at300K andfound to be the sensitive to the acceptor concentration. The mechanism ofroom-temperature ferromagnetism in the ZnO:(Mn,N) is discussed based on boundmagnetic polaron model.