Scanning Transmission Electron Microscopy Thesis

Scanning Transmission Electron Microscopy Thesis-29
Das Ziel der vorliegenden Arbeit ist es, ein besseres Verständnis der Struktur und Zusammensetzung dieser Defekte sowie ihrer Entwicklung während des CIGS-Wachstums zu erlangen.Die höchste Effizienz für CIGS-Solarzellen wird erreicht, wenn der CIGS-Absorber in einem dreistufigen Koverdampfungsprozess hergestellt wird.

Das Ziel der vorliegenden Arbeit ist es, ein besseres Verständnis der Struktur und Zusammensetzung dieser Defekte sowie ihrer Entwicklung während des CIGS-Wachstums zu erlangen.Die höchste Effizienz für CIGS-Solarzellen wird erreicht, wenn der CIGS-Absorber in einem dreistufigen Koverdampfungsprozess hergestellt wird.

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The staff of the center carries out research tasks on-demand, offers training and provides hands-on support for practical applications.

Members of the electron microscopy group work on various research projects involving functional oxides, novel heterostructures for future semiconductor devices as well as in-situ and electron-holographic methods .

grain growth and defect annihilation, thus enabling higher conversion efficiencies.

Therefore, it is crucial to investigate the recrystallization and the evolution of the microstructure at the second-stage of the CIGS growth.

NRR was used to demonstrate sub-picometer precision in STEM images of single crystal Si and Ga N, the best reported in EM.

NRR was then used to measure the atomic surface structure of Pt nanoacatalysts and Au nanoparticles which revealed new bond length variation phenomenon of surface atoms.Polycrystalline Cu(In, Ga)Se2 (CIGS) based thin-film solar cells achieve power-conversion efficiencies of almost 23% on the laboratory scale, one of the highest among thin-film solar cells.The aim of further CIGS research and development is to reach conversion efficiencies of 25%, which is currently the efficiency of the best single-crystalline Si based solar cells.The composition of the absorber becomes Cu-rich ([Cu]/([In] [Ga]) 1) during this stage.The change in composition leads to recrystallization, i.e.In Ga N thin films and In Ga N / Ga N quantum wells (QW) for light emitting diodes are the second major topic.Low-dose Z-contrast STEM, PACBED, and EDS on In Ga N QW LED structures grown by metal organic chemical vapor phase deposition show no evidence for nanoscale composition variations, contradicting previous reports.This thesis reports studies of electronic and nanostructured materials by advanced electron microscopy (EM) techniques, including scanning transmission electron microscopy (STEM), position averaged convergent beam electron diffraction (PACBED), X-ray energy dispersive spectroscopy (EDS), and electron energy loss spectroscopy (EELS).This work enhanced the understanding of the microstructure, defects, and composition of Ga-doped Zn O thin films, Sb-doped Zn O nanowires, and In Ga N quantum well (QW) based light emitting diode (LED) structures, and helped develop structure ? A new technique, non-rigid registration of STEM images, was developed and applied to make high-precision measurements of the atomic structure of Pt nanocatalysts and Au nanoparticles, and to improve the quality of STEM EDS spectrum images. Ga-doped Zn O is a candidate transparent conducting oxide material.The microstructure of GZO thin films grown by molecular beam epitaxy under metal-rich conditions on sapphire, O-rich conditions on sapphire, and metal-rich conditions on Ga N were examined using various EM techniques.The microstructure, prevalent defects, and polarity in these films strongly depend on the growth conditions and substrate.

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