Fe掺杂SnO2纳米晶薄膜的微观结构和性能

Microstructure and Properties of Fe-doped SnO_2 Nanocrystalline Films

采用反应磁控溅射法制备了Fe掺杂的SnO_2薄膜.沉积衬底为(100)的单晶硅,基片温度270℃,Ar为溅射气体.使用XRD,AFM和VSM研究氧分压对薄膜晶体结构和室温磁性能的影响.实验表明,氧分压为0.12Pa时,溅射得到的化学成分为Sn_(0.975)Fe_(0.025)O_(2-δ)的薄膜样品具有明显的室温铁磁性,平均饱和原子磁矩达到1.8μ_B/Fe.通过HRTEM和EDS分析了此样品的显微结构和成分分布,实验结果表明,薄膜由粒径3～7nm的纳米晶构成,为四方金红石SnO_2相;Fe元素分布较为均匀,排除了磁性能是由第二相产生的可能;同时由于薄膜电阻率接近于绝缘体,室温磁性能不是由载流子诱导机制形成的,而与晶格内部大量缺陷的存在密切相关.

Fe-doped SnO2 films were grown on Si （100） substrates at 270℃ by reactive magnetron sputtering. The sputtering atmosphere was a mixture of argon and oxygen. The samples were prepared under three different oxygen partial pressures. XRD, AFM, VSM were used to investigate the crystalline structure, surface morphology and room temperature ferromagnetism （RTFM） of the samples, respectively. The film deposited under oxygen partial pressure of 0.12Pa exhibits a clear ferromagnetism at room temperature. The chemical composition of the film is Sn0.975Fe0.025O2-δ, and the saturated magnetic moment is about 1.8μB/Fe. The microstructure and element distribution of this sample were examined by HRTEM and EDS, respectively. It shows that the films are composed of tetragonal rutile SnO2 nanocrystals with diameter of 3-7nm. Fe atoms are uniformly distributed in the films. No Fe metallic clusters or iron oxides are observed; the measurement of the resistivity indicates insulating characteristic of the film, therefore RTFM of the film can not be attributed to secondary phase or spin-chaxge carriers interaction. It shows that RTFM is closely related to a great number of structural defects in the film.