Caroline Hain

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Liquid metal infiltration of silicon based alloys into porous carbonaceous materials Part-III: Experimental verification of conversion products and infiltration depth by infiltration of Si-Zr alloy into mixed SiC/ graphite preforms

Caroline Hain, Manoj Kondibhau Naikade, Alberto Ortona, Ludger Weber

Porous carbonaceous preforms, made from graphite and silicon carbide (SiC) powders, with varying graphite powder mass fractions and particle sizes, were infiltrated at 1500 degrees C and 1700 degrees C by Si-8 at. pct Zr alloy to produce dense Si-Zr-SiC composites. The experiments were performed in a graphite chamber vacuum furnace at 10-2 mbar. The most desirable results were obtained for preforms composed of a mixture of graphite and SiC powders, with preforms containing 15-20 % mass fraction of graphite and infiltrated at 1500 degrees C. The banding of the Zr-rich phase observed in the cross-sections of SiC-C pre- forms infiltrated by the Si-Zr alloy may help in decoding the reactive infiltration process with binary alloys.

ELSEVIER SCI LTD2023

Plasma-Assisted Hybrid Vapour Deposition Technology for Thin Film Fabrication

Caroline Hain

Continuous development of thin film deposition technologies is essential for the fabrication of films that meet the specific requirements of their target applications and working conditions. Therefore, it is necessary to increase the number of accessible and tuneable process parameters, which can be achieved by venturing into the field of hybrid techniques. Among a variety of available deposition techniques, the focus of this work is on physical vapour deposition magnetron sputtering (PVD MS) methods, with the addition of microwave (MW) plasma. The main advantage of this work is its generalised approach to examining the "big picture" not only of film deposition itself, but also of the phenomena occurring at the material source, how they affect the deposition environment and the nature of the decoupled effects, and how they relate to film characteristics. With this in mind, the reader is first guided through selected plasma physics concepts necessary to follow the proposed hybrid vapour deposition (HVD) processes. The validity of this methodology is examined on the example of three material case studies, namely diamond-like carbon (DLC), indium nitride (InN) and zinc tin nitride (ZTN). Each case study explores the influencing factors of MS, starting with pulsed direct current magnetron sputtering (p-DCMS) through high power impulse magnetron sputtering (HiPIMS) and reactive HiPIMS (R-HiPIMS). Furthermore, the effects of incorporating the volume MW plasma (which fills the entire vacuum chamber) are investigated in the context of improving process control through tailored phenomenological decoupling, i.e. separation of otherwise interdependent effects. A range of in situ diagnostic techniques are used, including studying the obtained HiPIMS I(V,t) curves, time-resolved optical emission spectroscopy (OES), time-of-flight mass spectrometry (ToF-MS) and Langmuir probe measurements. The fabricated films were characterised in terms of the material's structure, micro- and nanostructure, as well as application properties. The obtained results highlight the significant contribution of MW plasma for enhancing phenomenon control during sputtering for all studied material cases.

EPFL2023

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The fabrication of high-hardness non-hydrogenated diamond-like carbon (DLC) via standard magnetron sputtering (MS) is often hindered by the low sputtering yields and ionisation rates of carbon, therefore investigations into pulsed alternatives of MS, else sputtered species post-ionisation methods, are of particular interest. This work focuses on investigating the influence of pulsed-direct current MS (pDCMS), high power impulse magnetron sputtering (HiPIMS) and their microwave plasma-assisted (MA-pDCMS, MA-HiPIMS) variants on the properties of the fabricated DLC films. Two setups were used for the pDCMS-and HiPIMS-based methods, respectively. The films were characterised using Raman spectroscopy, nanoindentation, X-ray reflectometry and scanning electron microscopy, where the pDCMS-produced films were additionally characterised by film-stress measurements. Moreover, in situ time-resolved Langmuir probe plasma analysis was performed under HiPIMS and MA-HiPIMS conditions to analyse the influence of the magnetron and microwave plasmas on one another. For both DCMSand HiPIMS-based procedures, it was found that the addition of microwave plasma did not facilitate attaining hardnesses beyond 30 GPa, however, it did enable modifying the morphology of the films. Furthermore, this study shows the potential of synchronised sputtering with substrate biasing, as well as the importance of microwave plasma source positioning in relation to the substrate.

ELSEVIER SCIENCE SA2022

Plasma-Assisted Hybrid Vapour Deposition Technology for Thin Film Fabrication

Caroline Hain

EPFL2023