Defect induced ferromagnetism in undoped ZnO nanoparticles
Defect induced ferromagnetism in undoped ZnO nanoparticles
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DOI：
10.1063/1.4867596
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发表时间：
2014-05-07
影响因子：
3.2
通讯作者：
Punnoose, A.
中科院分区：
文献类型：
--
作者：
Rainey, K.;Chess, J.;Punnoose, A.
以乙酸锌为前驱体，二甘醇(DEG)或变性乙醇[ZnO-I]为反应溶剂，采用强制水解法制备了尺寸约为12 nm的未掺杂纳米氧化锌(NPs)。在300K下，两种样品均表现出较弱的铁磁行为，饱和磁化强度M-S分别为0.077+/-0.002 Memu/g和0.088+/-0.013 Memu/g。傅立叶变换红外光谱(FTIR)表明，纳米晶的表面连接有二甘醇碎片。光致发光(PL)数据显示，氧化锌-Ⅱ在500 nm附近有一个宽广的发射，这在氧化锌-Ⅱ样品中是没有的，这可能是由于封顶分子对表面陷阱的阻挡。在流动的Ar气氛中于450℃下热处理，在氧化锌-I纳米粒子中产生有意的氧空位，使M-S逐渐增加，X射线光电子能谱(XPS)表明，氧空位可能在观察到的M-S的变化中起关键作用。最后，光致发光光谱显示了由锌间隙引起的蓝/紫发光，其强度随退火时间的变化而变化，与M-S的趋势相似。观察到的氧化锌纳米颗粒的磁化强度随Ar退火时间的变化似乎取决于锌间隙和氧空位数目的变化。(C)2014 AIP出版有限责任公司。
Undoped ZnO nanoparticles (NPs) with size similar to 12 nm were produced using forced hydrolysis methods using diethylene glycol (DEG) [called ZnO-I] or denatured ethanol [called ZnO-II] as the reaction solvent; both using Zn acetate dehydrate as precursor. Both samples showed weak ferromagnetic behavior at 300 K with saturation magnetization M-s = 0.077 +/- 0.002 memu/g and 0.088 +/- 0.013 memu/g for ZnO-I and ZnO-II samples, respectively. Fourier transform infrared (FTIR) spectra showed that ZnO-I nanocrystals had DEG fragments linked to their surface. Photoluminescence (PL) data showed a broad emission near 500 nm for ZnO-II which is absent in the ZnO-I samples, presumably due to the blocking of surface traps by the capping molecules. Intentional oxygen vacancies created in the ZnO-I NPs by annealing at 450 degrees C in flowing Ar gas gradually increased M-s up to 90 min and x-ray photoelectron spectra (XPS) suggested that oxygen vacancies may have a key role in the observed changes in M-s. Finally, PL spectra of ZnO showed the appearance of a blue/violet emission, attributed to Zn interstitials, whose intensity changes with annealing time, similar to the trend seen for M-s. The observed variation in the magnetization of ZnO NP with increasing Ar annealing time seems to depend on the changes in the number of Zn interstitials and oxygen vacancies. (C) 2014 AIP Publishing LLC.