Browsing by Author "Halindintwali, Sylvain"
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Item Effect of the annealing atmosphere on the layer interdiffusion in Pd/Ti/Pd multilayer stacks deposited on pure Ti and Ti-alloy substrates(University of the Western Cape, 2019) Halindintwali, Sylvain; Donald, Earl; Cummings, Franscious; Arendse, ChristopherPd(50 nm)/Ti(25 nm)/Pd(50 nm) multilayer stack has been deposited on Ti and Ti6Al4V substrates; we have studied the intermixing of layers upon annealing at the hydrogenation temperature of 550 °C, under vacuum, H/Ar gas mixture and pure hydrogen atmospheres. Scanning electron microscopy (SEM) micrographs indicated surface roughening in samples annealed under vacuum and H/Ar gas mixture while those annealed under pure H2 remained relatively smoother. Rutherford backscattering spectrometry (RBS) revealed intermixing of layers as evidenced by the diffusion of Pd toward the bulk, while XRD indicated the formation of PdTi2 phase in the samples annealed under vacuum and H/Ar gas mixture atmosphere. In-situ, real-time RBS showed that the annealing under pure H2 preserves the integrity of the Pd catalyst. No indication of the PdTi2 formation in the pure H2 annealed samples was observed; instead only the TiH2 phase appeared, indicating the absorption of H into the system.Item Solid state dewetting of a metal –semiconductor bi-layers deposited onto c-Si substrate(Springer, 2023) Halindintwali, Sylvain; Masenya, Madipoane; Madhuku, MorganA bi-layers stack consisting of a semiconductor thin film of a varied thickness and a very thin Pd layer (SiC/Pd/c-Si).was deposited onto c-Si by e-beam evaporation at room temperature. The multi-layers structure was subjected to a thermal annealing process at near eutectic temperature of the Si – Pd phase. It is noticed, through top view SEM and cross-section STEM analyses, that the sandwiched Pd metal layer dewets from the interface with the c-Si substrate in well dispersed nanoparticles and it diffuses inward onto the top few monolayers of the substrate; at times it permeates shallowly through the SiC semiconductor top layer. The size distribution of the nanoparticles was found to be closely linked to the thickness of the top semiconductor layer.Item A study of hydrogenated nanocrystalline silicon thin films deposited by hot-wire chemical vapour deposition (HWCVD)(University of the Western Cape, 2005) Halindintwali, Sylvain; Knoesen, Dirk; Dept. of Physics; Faculty of ScienceIn this thesis, intrinsic hydrogenated nanocrystalline silicon thin films for solar cells application have been deposited by means of the hot – wire chemical vapour deposition (HWCVD) technique and have been characterised for their performance. It is noticed that hydrogenated nanocrystalline silicon is similar in some aspects (mainly optical) to its counterpart amorphous silicon actually used as the intrinsic layer in the photovoltaic industry. Substantial differences between the two materials have been found however in their respective structural and electronic properties. We show that hydrogenated nanocrystalline silicon retains good absorption coefficients known for amorphous silicon in the visible region. The order improvement and a reduced content of the bonded hydrogen in the films are linked to their good stability. We argue that provided a moderate hydrogen dilution ratio in the monosilane gas and efficient process pressure in the deposition chamber, intrinsic hydrogenated nanocrystalline silicon with photosensitivity better than 102 and most importantly resistant to the Staebler Wronski effect (SWE) can be produced. This work explores the optical, structural and electronic properties of this promising material whose study – samples have been exclusively produced in the HWCVD reactors based in the Solar Cells laboratory of the Physics department at the University of the Western Cape.