Biedermann A, Schmid M, Reichl B M, Varga P
Institut für Allgemeine Physik, Technische Universität Wien, Wiedner Hauptstrasse 8-10, A-1040, Wien, Austria.
Anal Bioanal Chem. 1995 Oct;353(3-4):259-62. doi: 10.1007/s0021653530259.
Annealing an Fe(96.5)Si(3.5) (100)/(110) bicrystal, containing 90 ppm P, leads immediately to a strong segregation of silicon. The Si atoms, however, desegregate subsequently and are displaced by P, whose segregation enthalpy is larger than that of silicon. The corresponding surface structures formed on both faces have been studied using complementary methods: Scanning tunneling microscopy (STM) to obtain atomically resolved geometrical information and Auger electron spectroscopy (AES) for the determination of the surface composition. Si substitutes surface Fe atoms on both faces and forms ordered surface alloys, whereas P occupies hollow sites on the surface. Si and P form c(2 x 2) superstructures on the (100) surface, whereby each segregated phosphorus atom blocks in the average one silicon segregation site. The (110) surface, on the other hand, is characterized by a c(1 x 3) Si superstructure. Due to the anisotropy of this surface the P/Si exchange proceeds by the formation of silicon coverage decreasing domain boundaries within the silicon structure, which are simultaneously occupied by P atoms. Furthermore the comparison of the AES and STM derived phosphorus coverages indicates a P multilayer segregation on the (110) surface.
对含有90 ppm磷的Fe(96.5)Si(3.5) (100)/(110)双晶进行退火处理，会立即导致硅的强烈偏析。然而，硅原子随后会解偏析，并被磷取代，磷的偏析焓大于硅的偏析焓。使用互补方法研究了在两个面上形成的相应表面结构：利用扫描隧道显微镜（STM）获取原子分辨的几何信息，并利用俄歇电子能谱（AES）测定表面成分。硅取代了两个面上的表面铁原子并形成有序表面合金，而磷占据表面的空位。硅和磷在(100)表面形成c(2×2)超结构，平均每个偏析的磷原子会阻塞一个硅偏析位点。另一方面，(110)表面的特征是c(1×3)硅超结构。由于该表面的各向异性，磷/硅交换通过在硅结构内形成硅覆盖率降低的畴界来进行，这些畴界同时被磷原子占据。此外，对AES和STM得出的磷覆盖率的比较表明，在(110)表面存在磷的多层偏析。
