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Partial shielding by means of local gas supply has proven to be very effective in reducing spatter. Besides the effect of gas-induced dynamic pressure, the shielding of oxygen is also highly relevant for melt pool dynamics and spatter formation due to the growth of oxides and the influence on surface tension. Therefore, this paper addresses the effect of local supplied argon on oxide growth and seam topography during keyhole mode laser beam welding of high-alloy steel AISI 304. To determine the shielding quality, the results are compared to laser beam welding in a global argon atmosphere. The topography of the upper weld seams was analyzed by scanning electron microscopy (SEM). An X-ray microanalysis (EDX) in line scan modus was performed to determine and to locate the elements which are covering the specimen surface. The chemical state of the found elements was quantified by X-ray photoelectron spectroscopy (XPS). In a last step, high-speed synchrotron X-ray imaging was performed to separate the effect of the gas-induced pressure and the gas-induced shielding on keyhole geometry. The results show that a local supply of argon contributes to a significant difference in oxide growth, affecting melt pool convection and weld seam geometry. It was further shown that the effect of gas flows at low flow rates is primarily because of oxygen shielding, as no significant difference in keyhole geometry was found by high-speed synchrotron X-ray imaging.

Schichten und Beschichtungen sind mittlerweile eine unabdingbare Voraussetzung für eine Vielzahl von technischen Anwendungen für hochwertige Werkstoffe geworden. In diesem Beitrag werden beispielhaft hochwertige Beschichtungen für elektrisch leitende und optisch transparente Schichten für die Photovoltaik, Schichten für medizinische Elektroden, für Halbleiterkontakte und für Hochtemperaturkontakte vorgestellt. Die hierfür eingesetzten Verfahren sind das Magnetron‐Sputtern und die gepulste Laserdeposition. Der Einfluss der Beschichtungsparameter auf die funktionalen Eigenschaften werden vorgestellt.

In the present work cubic 3C-(Si1-xC1-y)Gex+y solid solutions were grown at different^temperatures by molecular beam epitaxy on on-axis 4H-SiC (0001) substrates. Two different growth methods are compared in order to explore the optimal growth conditions for the incorporation of Ge into the SiC lattice during the low temperature epitaxy. For this reason simultaneous growth and migration enhanced epitaxy were used. The chemical composition of the grown layers were analyzed by energy dispersive x-ray methods during transmission electron microscopy investigations. It was found that the migration enhanced epitaxy is a more suitable technique for the formation of high quality (Si1-xC1-y)Gex+y solid solutions. Additionally, polytypes transition from 4H-SiC to 3C-SiC occurs during the growth independent of the applied growth technique.

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Secondary ion mass spectroscopy, Fourier transformed infrared spectroscopy, ellipsometry, reflection high energy diffraction and transmission electron microscopy are used to gain inside into the effect of Ge on the formation of ultrathin 3C‐SiC layers on Si(111) substrates. Accompanying the experimental investigations with simulations it is found that the ultrathin single crystalline 3C‐SiC layer is formed on top of a gradient Si1–x–yGexCybuffer layer due to a complex alloying and alloy decomposition processes promoted by carbon and germanium interdiffusion and SiC nucleation. This approach allows tuning residual stress at very early growth stages as well as the interface properties of the 3C‐SiC/Si heterostructure. Useful yields of secondary ions of Ge in Si matrix and Si dimer are estimated. Secondary ion mass spectroscopy, Fourier transformed infrared spectroscopy, reflection high energy electron diffraction, ellipsometry, and transmission electron microscopy investigations are used to gain inside into the effect of Ge on the chemoheteroepitaxy of 3C‐SiC on Si(111). Experimental investigations and simulations demonstrate the formation of a ultrathin single crystalline 3C‐SiC layer on a gradient Si1–x–yGexCybuffer layer due to an alloying and alloy decomposition promoted by carbon and germanium interdiffusion and SiC nucleation. This approach allows tuning residual stress and the interface at very early growth stages.

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