Determination of Surface Atomic Structures of Bi₂se₃(111)-(2x2) Film and Zno Nano-Rods by Low Energy Electron Diffraction PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Determination of Surface Atomic Structures of Bi₂se₃(111)-(2x2) Film and Zno Nano-Rods by Low Energy Electron Diffraction PDF full book. Access full book title Determination of Surface Atomic Structures of Bi₂se₃(111)-(2x2) Film and Zno Nano-Rods by Low Energy Electron Diffraction by Wing-Lun Chung. Download full books in PDF and EPUB format.
Author: Wing-Lun Chung Publisher: Open Dissertation Press ISBN: 9781361381984 Category : Languages : en Pages :
Book Description
This dissertation, "Determination of Surface Atomic Structures of Bi₂Se₃(111)-(2X2) Film and ZnO Nano-rods by Low Energy Electron Diffraction" by Wing-lun, Chung, 鍾詠麟, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: The emergence of topological insulators and nano-materials brings the importance of surface science to a new level. The properties of topological insulator depend strongly on surface state. The novel properties of nano-materials are strictly related to their surfaces structure due to the large surface-area-to-volume ratio. In this thesis, I investigated the surface morphology of the Bi2Se3(111)-(2x2) reconstruction and the ZnO nano-rods by means of low energy electron diffraction(LEED). Bi2Se3(111)-(2x2) was prepared by molecular beam epitaxy, and the reconstruction is believed to be caused by Se adsorption. An atomic model with Se on the top site is proposed by the virtue of multiple incidence angles LEED IV Patterson inversion. Well aligned ZnO nano-rods array were prepared by template-assisted hydrothermal growth and vapour phase transport growth. Nono-rods prepared by vapour phase transport method were able to give the LEED IV spectra. The side facet orientation is found to be {101 ̅0} in the LEED perspective. The peak shifts of nano-rod IV spectra suggest that the nano-rods undergo a different extent of relaxation compared with that of single crystal. Here, I emphasise it is the first ever successful extraction of LEED IV from free standing nano-material surfaces. Although the above proved LEED is a powerful technique in surface morphology analysis, conventional LEED optics suffers electric charge up when probing high-resistivity material. In order to bring LEED to its widest potential, microchannel plate low energy electron diffraction (MCP-LEED) system was implemented. MCP-LEED avoids the charge up by bringing the electron beam current further down to the order of nA, when compared with mA of the conventional LEED system. An automate LEED data acquisition scheme was installed on the MCP-LEED system and the validity of the MCP-LEED system was verified by comparing its LEED IV spectra with that of the conventional LEED. The capability of MCP-LEED is justified by probing the high-resistivity ZnO single crystal manufactured by Tokyo Denpa. Pros and cons, as well as suggested future improvements of MCP-LEED are discussed. DOI: 10.5353/th_b5295506 Subjects: Low energy electron diffraction Bismuth compounds - Surfaces Atomic structure Zinc oxide - Surfaces
Author: Wing-Lun Chung Publisher: Open Dissertation Press ISBN: 9781361381984 Category : Languages : en Pages :
Book Description
This dissertation, "Determination of Surface Atomic Structures of Bi₂Se₃(111)-(2X2) Film and ZnO Nano-rods by Low Energy Electron Diffraction" by Wing-lun, Chung, 鍾詠麟, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: The emergence of topological insulators and nano-materials brings the importance of surface science to a new level. The properties of topological insulator depend strongly on surface state. The novel properties of nano-materials are strictly related to their surfaces structure due to the large surface-area-to-volume ratio. In this thesis, I investigated the surface morphology of the Bi2Se3(111)-(2x2) reconstruction and the ZnO nano-rods by means of low energy electron diffraction(LEED). Bi2Se3(111)-(2x2) was prepared by molecular beam epitaxy, and the reconstruction is believed to be caused by Se adsorption. An atomic model with Se on the top site is proposed by the virtue of multiple incidence angles LEED IV Patterson inversion. Well aligned ZnO nano-rods array were prepared by template-assisted hydrothermal growth and vapour phase transport growth. Nono-rods prepared by vapour phase transport method were able to give the LEED IV spectra. The side facet orientation is found to be {101 ̅0} in the LEED perspective. The peak shifts of nano-rod IV spectra suggest that the nano-rods undergo a different extent of relaxation compared with that of single crystal. Here, I emphasise it is the first ever successful extraction of LEED IV from free standing nano-material surfaces. Although the above proved LEED is a powerful technique in surface morphology analysis, conventional LEED optics suffers electric charge up when probing high-resistivity material. In order to bring LEED to its widest potential, microchannel plate low energy electron diffraction (MCP-LEED) system was implemented. MCP-LEED avoids the charge up by bringing the electron beam current further down to the order of nA, when compared with mA of the conventional LEED system. An automate LEED data acquisition scheme was installed on the MCP-LEED system and the validity of the MCP-LEED system was verified by comparing its LEED IV spectra with that of the conventional LEED. The capability of MCP-LEED is justified by probing the high-resistivity ZnO single crystal manufactured by Tokyo Denpa. Pros and cons, as well as suggested future improvements of MCP-LEED are discussed. DOI: 10.5353/th_b5295506 Subjects: Low energy electron diffraction Bismuth compounds - Surfaces Atomic structure Zinc oxide - Surfaces
Author: 楊暘 Publisher: ISBN: 9781361279571 Category : Languages : en Pages :
Book Description
This dissertation, "Atomic Structure Studies of Zinc Oxide (0001) Polar Surface by Low Energy Electron Diffraction at Multiple Incident Angles" by Yang, Yang, 楊暘, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Zinc oxide surfaces have been of considerable interest because of their favorable properties, such as high electron mobility, good transparency, large electronic breakdown field and wide bandgap. Knowing the surface structure of ZnO is the key to better understand the above phenomena and to further develop its applications. In this thesis, the Patterson Function was evaluated by inversion of LEED I-V spectra at multiple incident angles to determine the surface structure of the ZnO(0001) polar surface. The sample was prepared by degassing and then 15 cycles of argon sputtering and annealing. The experimental LEED I-V spectra from multiple incident angles were taken from the sample. After processing the data by a macro program in OPTIMAS and a Matlab program, a clean Patterson Function map showing the inter-atomic pair distances was obtained. It was then compared with the simulated Patterson Function map of the proposed 11 bare surface model. As a result, the spots positions in the simulated Patterson Function map matched well with that of the experimental Patterson Function map. On the other hand, the LEED I-V curve fitting work was done by the surface science group of City University of Hong Kong. Six models were proposed by them and normal incidence theoretical LEED I-V spectra were calculated to fit with the experimental LEED I-V curves provided by us. Among the six models 22 Zn point defect model was fitted to be the best model with the R-factor 0.244. We also compared the multiple scattering simulated Patterson Function map of 22 Zn point defect model with the experimental one to verify the validity of the model. As a result, the model fit the experimental data. So we conclude that in general 11 model support the order part, and 22 top layer Zn defect model best fits the random missing part. DOI: 10.5353/th_b4819951 Subjects: Zinc oxide - Surfaces Low energy electron diffraction
Author: Weerasinghe Priyantha Publisher: ISBN: Category : Epitaxy Languages : en Pages : 278
Book Description
"In this study, attempts were made to grow well-ordered chromium- and iron-oxide films on Ag(111) and Ag(001) surfaces, respectively, Two sample preparation techniques, multilayer growth and sequential growth, were used to grow these transition metal oxide films"--Abstract, leaf iii.
Author: Publisher: ISBN: Category : Languages : en Pages : 20
Book Description
Many properties of zinc oxide, including wide bandgap semiconductivity, photoconductivity, and chemical sensing, make it a very promising material for areas such as optoelectronics and sensors. This research involves analysis of the formation, or nucleation, of zinc oxide by electrochemical deposition in order to gain a better understanding of the effect of different controlled parameters on the subsequently formed nanostructures. Electrochemical deposition involves the application of a potential to an electrolytic solution containing the species of interest, which causes the ions within to precipitate on one of the electrodes. While there are other ways of forming zinc oxide, this particular process is done at relatively low temperatures, and with the high amount of x-ray flux available at SSRL it is possible to observe such nucleation in situ. Additionally, several parameters can be controlled using the x-ray synchrotron; the concentration of Zn{sup 2+} and the potential applied were controlled during this project. The research involved both gathering the X-ray diffraction data on SSRL beamline 11-3, and analyzing it using fit2d, Origin 6.0 and Microsoft Excel. A time series showed that both the in-plane and out-of-plane components of the ZnO nanorods grew steadily at approximately the same rate throughout deposition. Additionally, analysis of post-scans showed that as potential goes from less negative to more negative, the resulting nanostructures become more oriented.
Author: Chalk River Nuclear Laboratories. Reactor Materials Research Branch Publisher: Chalk River, Ont. : Reactor Materials Research Branch, Chalk River Laboratories ISBN: 9780660167022 Category : Oxide coating Languages : en Pages : 13
Author: Wing-Lun Chung
Author: Wing-Lun Chung
Author: 鍾詠麟
Author: 楊暘
Author: 楊暘
Author: Yang Yang (M. Phil.)
Author: Weerasinghe Priyantha
Author: 
Author: C. B. Duke
Author: 
Author: Chalk River Nuclear Laboratories. Reactor Materials Research Branch