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Strontium silicon surface by scanning tunneling microscopy system

Author: DuWenHan
Tutor: WangBing
School: University of Science and Technology of China
Course: Condensed Matter Physics
Keywords: Scanning tunneling microscopy Sr / Si surface Electronic structure and geometry Quasi- one -dimensional motion
CLC: O469
Type: PhD thesis
Year: 2009
Downloads: 141
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Abstract


Sr / Si surface of the system in the crystalline oxide - semiconductor epitaxial growth system has an important role. By means of scanning tunneling microscopy (STM) of this powerful tool for surface science, this in-depth study of the different Sr / Si reconstructed surface geometry and electronic structure. We found that the Sr / Si (100) -2 × '1 'and Sr / Si (111) -3 × 2 in two different configurations on the surface and then strontium atoms, at room temperature, have a silicon atoms from the surface and then along a structure in a channel formed quasi-one-dimensional motion of physical properties. In Sr / Si (100) -2 × 3 configuration exists then 2 × direction along the re-formed silicon dimers. Also in the Sr / Si (100) -2 × 1 substrate, we SrTiO3 thin films by annealing treatment, observed a significant re-structure features metallic nano-islands, we believe that through the analysis of these islands have TiSi2 structure, thereby further understanding of silicon oxide during the epitaxial growth of the interface reaction properties. The main contents include: Chapter I: Summary of previous work mainly and discuss issues related to the purpose of our study leads, and gives sample preparation methods and corresponding technical principles. Chapter II: The main research in ultrathin SrO / Si (100) membrane to the Sr / Si (100) reconstructed the dynamic process of transformation. By photoelectron spectroscopy (XPS) we find in the conversion process, the intermediate existence of SrO is the physical phenomenon of crystallization. High dynamic STM scan finds from SrO / Si (100) to the Sr / Si (100) occurs during the conversion of two typical state: first from the rough surface of the amorphous state to a smooth transition from the amorphous state and then to atomically flat Sr / Si (100) reconstructed surface transformation. As different annealing time, temperature observed in the Sr / Si (100) -2 × 3 and Sr / Si (100) -2 × 1 Two typical reconstructed surface. Further annealing treatment on the surface to continue to reduce the formation of strontium Sr atomic chain movement. Chapter III: The main research Sr / Si (100) surface geometry and electronic structure, and to study the initial oxidation of the surface too. At room temperature to obtain the Sr / Si (100) -2 × 3 scanning tunneling spectroscopy and dI / dV image, combined with first-principles theoretical calculations, we further give Sr / Si (100) -2 × 3 surface geometry. The reconstructed surface is formed in the process, as part of a substrate of silicon atoms in the dimerization bond breaking occurs rearrangement to form a new silicon dimers, strontium atom and a silicon atom will be apparent such a charge transfer phenomenon, which it explains why the reconstructed surface silicon atoms XPS results show that it is in the dimerization state, and previous theoretical results but their conflicting issues. On the basis of the clearly structured, we study the initial oxidation of the surface mechanisms: through different oxygen coverage analysis, we found a total of four typical oxide structure. Combined with theoretical calculations, we believe that the structure of these four oxidation, all three molecular oxygen oxidation of belonging to a single result, the other one is the oxidation of molecular dioxygen results, and the molecular oxygen oxidation of double structures exhibit typical metallic electronic structure properties. Chapter 4: The main research Sr / Si (100) -2 × 1 surface. Through high-resolution STM image of observation, we found that Sr / Si (100) -2 × 1 surface has a typical bias dependence, we give further structural model of the surface. By room-temperature and low temperature (80K) the Sr / Si (100) -2 × 1 STM image of the surface of the continuous scanning, we found that the surface of strontium atoms at room temperature a clear migration phenomenon, these migrations can strontium frequent Empty high bias voltage and the unoccupied states formed under vague atomic chain, through careful analysis, we believe that the migration of strontium at room temperature dimerization mainly along a channel formed silicon atom chain direction, so that the surface exhibits a one-dimensional motion physical properties. Chapter V: The main research Sr / Si (111) -3 × 2 reconstructed surface. We annealed Si (111) -7 × 7 SrO deposited on a substrate prepared by ultra-thin Sr / Si (111) -3 × 2 reconstructed surface. STM through the surface morphology and electronic structure analysis, we believe Sr / Si (111) -3 × 2 reconstructed surface structure model of HCC constituted. In a typical temperature STM image can be observed and clarity of the surface atomic chain alternately blur phenomenon. STM scanning through the dynamic, we find the atomic chain is blurred due to a silicon atom, strontium atom form a double bond along a one-dimensional groove movement which indicates that the surface has one-dimensional movement of the physical properties. Chapter VI: in Sr / Si (100) -2 × 1 on the substrate, using the PLD SrTiO3 thin films were deposited by a few nanometers obtained after annealing multilayer nano-islands, the kinds of the electronic structure of nano-islands showed significant metallic. By collecting dI / dV images found on the surface of the island under different energy electron distribution was significantly different. STM image was also observed in a particular surface will bias the morphology of trimer. Through analysis, we believe that the nano-islands are arranged by the C54-TiSi2 structure formed, and different biases STM topography image of Ti and Si, respectively, reflecting the electronic states of atoms information.

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