Fe离子注入ZnO产生的缺陷及磁学性能研究

A Study on the Fe-Implantation Induced Defects in ZnO and Its Magnetic Properties

氧化锌(ZnO)单晶在室温下注入了能量在50～380keV之间,总剂量为1.25×1017/cm2的Fe离子.利用慢正电子束技术研究了离子注入产生的缺陷.正电子湮没多普勒展宽测量表明,离子注入产生了大量的空位团.在经过400℃以下的较低温度退火后,这些空位团的尺寸进一步增大,随后在高温退火后空位团开始恢复,经过700℃以上退火后大部分缺陷已经消失,而在1 000℃退火后,所有离子注入产生的缺陷得到消除.X射线衍射测量也表明离子注入产生了晶格损伤,且经过700℃退火后基本得到恢复.另外,在700℃退火的注入样品中还观察到金属Fe的衍射峰,表明Fe离子注入ZnO形成了Fe团簇.磁学测量显示Fe注入的ZnO中表现出了铁磁性.经过700℃高温退火后其磁性并没有发生明显变化.这说明Fe离子注入的ZnO中缺陷对其铁磁性没有影响,铁磁性可能来源于注入的Fe离子.

ZnO single crystal was implanted with Fe ions of energy between 50～380 keV up to a total dose of 1.25×10^17/cm^2.The implantation induced defects were studied using a slow positron beam.The Doppler broadening measurements show that implantation introduces a large number of vacancy clusters.After annealing at temperatures lower than 400 ℃,these vacancy clusters grow to a larger size.Further annealing causes the recovery of these defects.After annealing at above 700 ℃,most of the defects are removed,and after annealing at 1 000 ℃,nearly all the implantation induced defects disappear.X-ray diffraction measurements also reveal the lattice damage after ion implantation,and the damage can be recovered after annealing at 700 ℃.Diffraction patterns of Fe metals are also observed after annealing,indicating formation of Fe nanoclusters in the Fe-implanted ZnO.Magnetic measurements reveal ferromagnetism in the Fe-implanted ZnO,and the magnetization becomes stronger with the decreasing temperature.After annealing the implanted sample at 700 ℃,the ferromagnetism has no apparent change.This indicates that the implantation induced defects has no influence on the magnetic properties.Ferromagnetism might be due to the substitution of the Zn lattice by the implanted Fe ions.