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Effect of deposition parameters on silicon layers transition from amorphous phase to micro/nano-crystalline phase in different deposition techniques

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2013
Nogay, Gizem
Hydrogenated nano/micro-cystalline silicon (nc-/c-Si:H) thin films are the key materials for Si-based thin film solar cell technology. These films have attracted great attention due to their applications in thin film solar cells. Silicon phase transition from amorphous to nano/micro-crystalline phase is an important phenomenon, especially in progress of Si thin film tandem structured solar cells. It is well-accepted fact that the development of deposition phase diagrams allows phase engineering for systematic improvement of materials and cell structures. In this thesis, crystallization dynamics of the amorphous silicon prepared via different deposition techniques such as magnetron sputtering, electron beam evaporation, CCP-assisted CVD and ICP-assisted CVD have been investigated. The advantages and disadvantages of these production methods have been debated by considering different aspects such as cost efficiency, film uniformity, deposition rate and applicability. For each technique, different deposition parameters such as deposition power, pressure, coating duration, substrate temperature, and source gas dilution were investigated comprehensively. Deposited films were analyzed in structural, morphological, optical and electrical features. Films are deposited on different substrate such as glass, quartz and Si-wafer and basic diagnostic tools like Raman Spectroscopy (RS), Grazing Incidence X-Ray Diffraction (GR-XRD), X-Ray Photoelectron Spectroscopy (XPS), Spectroscopic Ellipsometry (SE), Fourier Transform Infra-Red Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM) are used as complementary methods. Crystalline volume fraction calculated by RS is assumed as the key parameter while defining the structural transition. At the end of this research, general knowledge about the crystallization parameters for different chemical and physical vapor deposition techniques was obtained. .