Mn 掺杂 SiC 基稀磁半导体薄膜的结构和磁性研究

目的从原子水平探究Mn掺杂SiC薄膜的磁性起源。方法采用射频磁控溅射技术制备不同掺杂浓度的Mn掺杂SiC薄膜,并采用X射线衍射技术、X光电子能谱、同步辐射X射线近边吸收精细结构技术、物理性质测试系统对薄膜的结构、组分和磁性能进行研究。结果晶体结构和成分分析表明,1200℃退火后的薄膜形成了3C-SiC晶体结构,且随着Mn掺杂浓度的增加,3C-SiC晶体的特征峰向低角度移动。在Mn掺杂浓度(以原子数分数计)为3%,5%,7%的薄膜中,掺杂的Mn原子以Mn2+的形式存在;而在9%Mn掺杂的SiC薄膜中,则有第二相化合物Mn4Si7形成。局域结构分析表明,薄膜中均不存在Mn金属团簇和氧化物,在3%,5%和7%Mn掺杂的薄膜中,掺杂的Mn原子主要以代替C位的形式进入3C-SiC晶格中,而在9%Mn掺杂的薄膜中,掺杂的Mn原子以C替位形式和Mn4Si7共存。磁性测试表明,制备的Mn掺杂SiC薄膜具有室温铁磁性,且饱和磁化强度随着Mn掺杂浓度的提高而增加。结论薄膜的室温铁磁性是本征的,磁性来源与掺杂的Mn原子以Mn2+取代SiC晶格中C位后导致的缺陷有关,符合缺陷导致的束缚磁极子机制。

Investigation of Structure and Magnetic Properties of Mn-doped SiC Dilute Magnetic Semiconductors

ABSTRACT:Objective To investigate the magnetic origin of Mn-doped SiC films from the atom level. Methods The films of Mn-doped SiC were fabricated by radio frequency-magnetron sputtering. The structure, components and magnetic properties of films were investigated by X-ray diffraction ( XRD) , X-ray photoelectron spectroscopy ( XPS) , X-ray absorption fine structure ( XAFS) and physical property measuring system ( PPMS) , respectively. Results The analysis of crystal structure and composition showed that the structure of 3C-SiC was formed in the films after 1200 ℃ anneal, and with the increasing of Mn content, the characteristic peaks of 3C-SiC moved to lower angle. In 3%, 5% and 7% Mn-doped SiC films, the doping Mn atoms existed in the form of Mn2+ions, but in 9% Mn-doped SiC film, the second phase of compound Mn4 Si7 appeared. The study of local structure of films showed that there were no Mn clusters or Mn-related oxides. The doped Mn atoms existed in the form of substitution for C sites in 3C-SiC lattice in 3%, 5% and 7% Mn-doped SiC films, and in 9% Mn-doped SiC film there was a coexistence of C substitution and com-pound Mn4 Si7 . The magnetic measurement by PPMS showed that the Mn-doped SiC films were ferromagnetic at room temperature, and the saturation magnetization increased with the increasing of Mn content. Conclusion The magnetism of films is intrinsic and relevant to the defects caused by Mn in the form of Mn2+substituted for C in 3C-SiC lattice and is accorded with the bound magnetic polarons ( BMP) mechanism accused by defects.