Scanning Transmission Electron Microscopy Thesis

Such recombination processes may occur at line or planar defects present in the CIGS absorbers (among other interfaces, such as absorber and buffer layer).In the present study, the structure and composition of several defects as well as their evolution during the growth were investigated for an enhanced understanding.

Such recombination processes may occur at line or planar defects present in the CIGS absorbers (among other interfaces, such as absorber and buffer layer).In the present study, the structure and composition of several defects as well as their evolution during the growth were investigated for an enhanced understanding.

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The defect consists of a faceted pyramid-shaped void that produces a threading dislocation along the [0001] growth direction, and is likely caused by carbon contamination during growth.Ein Ziel weiterer Forschung und Entwicklung auf dem Gebiet von CIGS-Solarzellen ist das Erreichen eines Wirkungsgrades von 25% und mehr, welchen monokristalline Silizium-Solarzellen aufweisen.Um dieses Ziel zu erreichen, sollten limitierende Faktoren, wie z. nichtstrahlende Rekombination von Ladungsträgern, reduziert werden. Solche Rekombinationsprozesse können an Versetzungen und planaren Gitterdefekten in den Absorbern (und an Grenzflächen wie diejenige zwischen Absorber und Pufferschicht) verstärkt auftreten.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.Highest efficiencies in CIGS solar cells are achieved, when the absorber is fabricated with a three-stage co-evaporation process.During the second stage of this process, Cu and Se are evaporated on the initially formed (In, Ga)2Se3 layer.In addition, NRR allowed for measuring the 3D atomic structure of the nanoparticles with less than 1 atom uncertainty, a long standing problem in electron microscopy.Finally, NRR was adapted to EDS spectrum images, significantly enhancing the signal to noise ratio and resolution of an EDS spectrum image of Ca-doped Nd Ti O3 compared to conventional methods.Non-rigid registration and high-precision STEM of nanoparticles is the final topic.Non-rigid registration (NRR) is a new image processing technique that corrects distortions arising from the serial nature of STEM acquisition that previously limited the precision of locating atomic columns and counting the number of atoms in each column in STEM images.