Surface and electronic properties of the Mn:Ge(1 1 1) interface at the early stages of growth

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• 作者：Alberto Verdini ; Albano Cossaro ; Luca Floreano ; Alberto Morgante ; Andrea Goldoni ; Damiano Ghidoni ; Aless ; ro Sepe ; Stefania Pagliara ; Luigi Sangaletti
• 关键词：Photoelectron diffraction measurements ; Reflection high-energy electron diffraction ; Synchrotron radiation photoelectron spectroscopy ; Metal– ; semiconductor interfaces ; Manganese ; Germanium
• 刊名：Surface Science
• 出版年：2006
• 出版时间：15 September 2006
• 年：2006
• 卷：600
• 期：18
• 页码：4369-4374
• 全文大小：1690 K

文摘

The surface structure and the electronic properties of the Mn:Ge(1 1 1) interface have been investigated by reflection high-energy electron diffraction (RHEED) and X-ray photoemission (XPS) and absorption spectroscopies (XAS) with the aim to characterize the growth process of an ordered Mn_xGe_1−x alloy upon annealing at temperatures between 130 °C and 430 °C. The Mn:Ge(1 1 1) interface has been produced by e-beam evaporation of Mn ions on a clean, c(2 × 8) reconstructed Ge(1 1 1) surface. After an Mn evaporation of 1.3 to 2 ML, annealing at about 300 °C yields a (√3 × √3)R30° surface reconstruction, while at higher temperatures the onset of c(2 × 8) reconstruction is found superimposed to the (√3 × √3)R30° pattern. X-ray photoelectron diffraction (PED) measurements have been carried out to identify the local environment around the Mn atoms, and a preliminary analysis indicates the occurrence of Mn diffusion beneath the surface, even in as-grown thin layers, without the formation of the Mn₅Ge₃ alloy. These findings indicate that Mn diffusion inside the Ge lattice can be regarded as an important mechanism in the formation of the Mn:Ge(1 1 1) interface. In this frame, the electronic properties of the interface are discussed. Once the effects of oxygen contaminations are ruled out, the system does not show a XAS spectrum characteristic of atomic Mn²⁺ 2p⁵3d⁶ multiplet, which excludes strong localization effects typical of diluted magnetic semiconductors. However, the lineshape of XAS spectrum indicates that some hybridization between the Mn ion and Ge is present.