Research Departments Solid State Quantum Electronics Research Spectral Imaging of Diffusing Ions Spectral Imaging of Diffusing Ions Electron Tunneling at High-Temperatures P. Ngabonziza, Y. Wang, P. A. van Aken, J. Maier, and J. Mannhart Two-dimensional Doping of Proton Conductors: BaZrO3-based Heterostructures P. Ngabonziza, R. Merkle, Y. Wang, P. A. van Aken, T. S. Bjørheim, J. Maier, and J. Mannhart