Density-functional study of Mn monosilicide on the Si(111) surface: Film formation versus island nucleation
Density-functional study of Mn monosilicide on the Si(111) surface: Film formation versus island nucleation
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Si(111) 表面上单硅化锰的密度泛函研究：成膜与岛形核
DOI：
10.1103/physrevb.76.235426
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发表时间：
2007
影响因子：
3.7
通讯作者：
M. Scheffler
中科院分区：
文献类型：
--
作者：
M. Hortamani;P. Kratzer;M. Scheffler
用密度泛函理论计算了Si_（111）表面Mn_（111）硅化物薄膜的稳定性和Mn_（111）硅化物小晶粒的稳定性。我们的计算扩展了以前对MnSi/Si 001的研究，表明Si 111上的MnSi膜具有相似的电子和磁性，即，在表面和界面附近的Mn原子处的大磁矩以及在费米能级处的高度自旋极化。因此，这种MnSi膜作为与硅相容的自旋电子学材料可能是令人感兴趣的。此外，从我们计算的总能量，我们得出结论，Si 111衬底应该比Si 001衬底更适合生长MnSi层。这一结果是通过分析三维3D MnSi岛的形成条件获得的，无论是B20晶体结构还是B2结构中的假晶岛：在Si 001上，3D岛，即使它们只有几个晶格常数宽，也被发现已经比均匀的MnSi膜更稳定。一个双金字塔的“冰山”岛组成的MnSi在B20结构的Si 001衬底上被发现是最稳定的结构中的调查。然而，对于Si 111上的MnSi，我们的计算表明，形成3D岛的核更大。因此，Mn沉积最初导致平坦的2D岛的形成。在Si 111上，发现这种岛的最低能量结构类似于块状MnSi的B20结构，而在Si 001上，这种结构与衬底晶格不相容。我们的结果与实验观察一致，在Si 111上形成了一个几乎封闭的33结构的薄膜，在Si 001上形成了三维岛。
The stability of thin films and of small crystallites of Mn monosilicide MnSi on the Si111 surface is investigated by density-functional theory calculations. Extending previous studies of MnSi/Si001, our calculations indicate that MnSi films on Si111 have similar electronic and magnetic properties, i.e., large magnetic moments at the Mn atoms near the surfaces and interfaces and a high degree of spin polarization at the Fermi level. Hence, such MnSi films could be interesting as a spintronics material compatible with silicon. Moreover, from our calculated total energies we conclude that the Si111 substrate should be more suitable to grow MnSi layers than the Si001 substrate. This result is obtained by analyzing the conditions for the formation of three-dimensional 3D MnSi islands, either in the B20 crystal structure or as pseudomorphic islands in the B2 structure: On Si001, 3D islands, even if they are just a few lattice constants wide, are found to be already more stable than a homogeneous MnSi film. A bipyramidal “iceberg” island consisting of MnSi in the B20 structure on the Si001 substrate is found to be most stable among the structures investigated. For MnSi on Si111, however, our calculations show that the nucleus for forming a 3D island is larger. Therefore, Mn deposition initially leads to the formation of flat 2D islands. On Si111, the lowest-energy structure for such islands is found to be similar to the B20 structure of bulk MnSi, whereas on Si001 this structure is incompatible with the substrate lattice. Our results are in agreement with the experimental observations, formation of an almost closed film with 33 structure on Si111, and 3D island formation on Si001.