• X-ray measurements were carried out on GaN/Si heterostructures and Cu polyheaters. At ESRF, several in-situ experiments on GaN-structures, partially also time-resolved at extremely high data rates, have been carried out using three different X-ray-based methods i.e. SXDM, XBIC and FFXDM.
• Within the X-ray based characterization task, the consortium has designed an in-situ setup for laboratory nano-X-ray tomography. The data allows 3D reconstruction and thus, the quantitative 3D visualizing of micro-cracks. Moreover, amongst others, the strain and mosaicity of individual Cu grains were mapped by DFXM. Lastly, an in-situ setup for TXM and DFXM has been developed which is currently employed in first lab-measurements. Last but not least, XBIC was verified as a method to detect electrical degradation.
• In terms of Electron-probe based characterization using SEM-based techniques like ECCI and HR-EBSD, simulation- and machine learning-based methods opened a path to characterize dislocations in active GaN top layers in a non-destructive way. This was confirmed by conventional indexation in TEM (Transmission Electron Microscopy). Beyond, time-resolved cathodoluminescence (TRCL) and electron-beam induced current (EBIC) methods are underway to discriminate and characterize harmless from potentially electrically active defects. The GaN-derived methods are being transferred to SiC samples, too.
• Copper-based metallic layers and contacts were tested under different conditions and boundary conditions (free- standing foils, sections attached on wafers, XRM and TEM polyheaters) to deeper understand their ageing mechanisms. In-situ and post-test analysis showed that the microstructure is evolving slowly under thermo-mechanical stresses and that pore formation depends most probably on grain boundary diffusion.
• Combined TEM in-situ experiments and FEM crystal plasticity calculations have demonstrated that dislocation movement-based mechanisms are not mainly responsible for the ageing of the metal under thermo-mechanical cycling.
• In modelling, a FEM solver for crystal plasticity modeling was adapted and existing multi-physics codes for simulations were re-structured to allow for additional solutions needed in AddMorePower. In addition, the simulation of wedge grain boundary arrangement for curved grain boundaries were modified. It showed that curved grain boundaries might be sufficient to produce tensile strains in the copper. Thus, hypotheses for degradation mechanisms in copper during thermal straining were developed. Moreover, first simulation results of elastic fields of single threading dislocation in GaN were presented.
For communication and dissemination, a website (AddMorePower.eu) social media channels and newsletter are actively used for external communication. For visual communication, a project video as well as video interviews with project partners were created.
