Electromobility is on the advance. A major problem on the road to electromobility is the capacity of the battery. Research is needed to increase this capacity. The surface properties of the cathode of lithium-ion batteries are particularly important. Characterisation of these surfaces by means of scanning electron microscopy (see Fig. 1) plays an essential role. The CiS Research Institute is involved in the SiekeV project (funded by the BMWi) to improve such scanning electron microscopes for the analysis of near-surface structures.
The SiekeV project aims to increase the quantum efficiency of silicon diodes with regard to the irradiation of low-energy electrons. By detecting low-energy electrons, it is possible to take very surface-sensitive scanning electron microscopy images. A real breakthrough has now been achieved in this project. The quantum efficiency of low-energy electrons with an energy of 1keV was increased from 2% for a standard pn diode to 75% for the newly developed electron detector (see Fig. 2). This was achieved by optimising the process parameters. New design rules could be created. The depth of the pn junction and the thickness of the cover layer system are essential. Both could be significantly reduced so that low-energy electrons can generate electron-hole pairs in the silicon with high quantum efficiency.