Tarasov Anton S, Tarasov Ivan A, Yakovlev Ivan A, Rautskii Mikhail V, Bondarev Ilya A, Lukyanenko Anna V, Platunov Mikhail S, Volochaev Mikhail N, Efimov Dmitriy D, Goikhman Aleksandr Yu, Belyaev Boris A, Baron Filipp A, Shanidze Lev V, Farle Michael, Varnakov Sergey N, Ovchinnikov Sergei G, Volkov Nikita V
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, 660036 Krasnoyarsk, Russia.
Institute of Engineering Physics and Radio Electronics, Siberian Federal University, 660041 Krasnoyarsk, Russia.
Nanomaterials (Basel). 2021 Dec 31;12(1):131. doi: 10.3390/nano12010131.
Three-layer iron-rich FeSi/Ge/FeSi (0.2 < < 0.64) heterostructures on a Si(111) surface with Ge thicknesses of 4 nm and 7 nm were grown by molecular beam epitaxy. Systematic studies of the structural and morphological properties of the synthesized samples have shown that an increase in the Ge thickness causes a prolonged atomic diffusion through the interfaces, which significantly increases the lattice misfits in the Ge/FeSi heterosystem due to the incorporation of Ge atoms into the FeSi bottom layer. The resultant lowering of the total free energy caused by the development of the surface roughness results in a transition from an epitaxial to a polycrystalline growth of the upper FeSi. The average lattice distortion and residual stress of the upper FeSi were determined by electron diffraction and theoretical calculations to be equivalent to 0.2 GPa for the upper epitaxial layer with a volume misfit of -0.63% compared with a undistorted counterpart. The volume misfit follows the resultant interatomic misfit of |0.42|% with the bottom Ge layer, independently determined by atomic force microscopy. The variation in structural order and morphology significantly changes the magnetic properties of the upper FeSi layer and leads to a subtle effect on the transport properties of the Ge layer. Both hysteresis loops and FMR spectra differ for the structures with 4 nm and 7 nm Ge layers. The FMR spectra exhibit two distinct absorption lines corresponding to two layers of ferromagnetic FeSi films. At the same time, a third FMR line appears in the sample with the thicker Ge. The angular dependences of the resonance field of the FMR spectra measured in the plane of the film have a pronounced easy-axis type anisotropy, as well as an anisotropy corresponding to the cubic crystal symmetry of FeSi, which implies the epitaxial orientation relationship of FeSi (111)[0-11] || Ge(111)[1-10] || FeSi (111)[0-11] || Si(111)[1-10]. Calculated from ferromagnetic resonance (FMR) data saturation magnetization exceeds 1000 kA/m. The temperature dependence of the electrical resistivity of a Ge layer with thicknesses of 4 nm and 7 nm is of semiconducting type, which is, however, determined by different transport mechanisms.
通过分子束外延在Si(111)表面生长了Ge厚度为4纳米和7纳米的三层富铁FeSi/Ge/FeSi（0.2＜ ＜0.64）异质结构。对合成样品的结构和形态特性进行的系统研究表明，Ge厚度的增加会导致原子通过界面的扩散时间延长，由于Ge原子掺入FeSi底层，这会显著增加Ge/FeSi异质系统中的晶格失配。表面粗糙度的发展导致总自由能降低，从而使上层FeSi从外延生长转变为多晶生长。通过电子衍射和理论计算确定，上层FeSi的平均晶格畸变和残余应力对于上层外延层相当于0.2吉帕，与未畸变的对应层相比，体积失配为-0.63%。体积失配与底部Ge层的原子间失配结果|0.42|%一致，这是通过原子力显微镜独立测定的。结构有序度和形态的变化显著改变了上层FeSi层的磁性，并对Ge层的输运特性产生微妙影响。对于Ge层厚度为4纳米和7纳米的结构，磁滞回线和铁磁共振（FMR）光谱都有所不同。FMR光谱显示出对应于两层铁磁FeSi薄膜的两条明显吸收线。同时，在Ge层较厚的样品中出现了第三条FMR线。在薄膜平面内测量的FMR光谱共振场的角度依赖性具有明显的易轴型各向异性，以及对应于FeSi立方晶体对称性的各向异性，这意味着FeSi（111）[0-11] || Ge(111)[1-10] || FeSi（111）[0-11] || Si(111)[1-10]的外延取向关系。根据铁磁共振（FMR）数据计算得出的饱和磁化强度超过1000千安/米。厚度为4纳米和7纳米的Ge层的电阻率温度依赖性为半导体类型，然而，这是由不同的输运机制决定的。
