1. Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH, Jülich 52428, Germany
2. International Iberian Nanotechnology Laboratory (INL), Braga 4715-330, Portugal
3. State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China