Mn离子注入Si材料的结构分析及磁学性质

采用剂量分别为1×10~(16)(1E16),3×10~(16)(3E16)和5×10~(16)cm~(-2)(5E16)的Mn离子注入方法制备Si基稀磁半导体样品.利用透射电子显微镜(TEM)和交变梯度磁强计(AGM)对不同剂量的样品退火前后的结构和磁学特性的变化进行了表征.实验发现,退火前,只有5E16样品出现球状偏析物,其直径在5 nm左右,但也有个别直径15 nm左右的大团簇.N_2环境下800℃退火5 min部分修复了1E16样品注入区域的晶格损伤,并使该剂量样品出现偏析物,直径多在10 nm左右.衍射花样分析表明该偏析物为具有晶面间距0.333,0.191和0.163 nm的微晶,这说明该微晶最有可能是MnSi_(1.7),退火前,样品饱和磁化强度随注入剂量增大而显著增强,但从3E16到5E16增速放缓,退火使低剂量样品磁性大幅减弱,说明偏析物不利磁性增强.

Structure Analysis and Magnetic Properties of Mn-Implanted Si

Mn implantation was performed with different dosages of 1×10~(16) (1E16), 3×10~(16)(3E16) and 5×10~(16)cm~(-2)(5E16)into p-Si(100)to prepare Si-based diluted magnetic semiconductor(DMS)samples. Transmission electron microscopy (TEM) and alternating gradient magnetometer (AGM) were utilized to characterize the structural and magnetic properties of both as-implanted samples and samples annealed at 800℃ in N_2 atmosphere for 5 min.The TEM images of non-annealed samples with fluences of 1×10~(16) cm~(-2),3×10~(16) cm~(-2) revealed no formation of precipitates.However,for the highest fluence (5×10~(16) cm~(-2),there are nanometer size clusters distributed throughout the implanted region.most of which had the diameters of ～5 nm,but several nanoparticles were as big as～15 nm.Annealing process partially helped recrystallize the implanted region of 1E16 sample,and was also responsible for the formation of precipitates(with diameters of ～10 nm).Analysis of the selected area diffraction pattern determined that the nanometer size precipitates were crystallites with the lattice spacing of 0.333,0.191 and 0.163 nm.These spacings indicate that the most probable phase of the crystallites is MnSi_(1.7).Before annealing,the saturation magnetization enhanced significantly with the increasing of the Mn fluence.The rising speed of saturation magnetization from 3×10~(16) cm~(-2) to 5×10~(16) cm~(-2) was less than that from 1×10~(16) cm~(-2) to 3×10~(16) cm~(-2),In addition,annealing procedure decreased the saturation magnetization of 1E16 sample to nearly zero.These facts indicate that the precipitates did not contribute to the sample magnetism.