The mechanism of caesium intercalation of graphene

Properties of many layered materials, including copper- and iron-based superconductors, topological insulators, graphite and epitaxial graphene can be manipulated by inclusion of different atomic and molecular species between the layers via a process known as intercalation. For example, intercalation in graphite can lead to superconductivity and is crucial in the working cycle of modern batteries and supercapacitors. Intercalation involves complex diffusion processes along and across the layers, but the microscopic mechanisms and dynamics of these processes are not well understood. Here we report on a novel mechanism for intercalation and entrapment of alkali-atoms under epitaxial graphene. We find that the intercalation is adjusted by the van der Waals interaction, with the dynamics governed by defects anchored to graphene wrinkles. Our findings are relevant for the future design and application of graphene-based nano-structures. Similar mechanisms can also play a role for intercalation of layered materials.Comment: 8 pages, 7 figures in published form, supplementary information availabl

Comparison Between CVD and ALE Produced TiO2 Cathodes in Zn/(PEO)4ZnCl2/TiO2,SnO2 or ITO Galvanic Cells

The way of preparation of thin films of TiO2 is extremely important regarding its application in electronic and optoelectronic devices. We have assembled Zn/(PEO)4ZnCl2/TiO2,SnO2 or ITO rechargeable galvanic cells using CVD (chemical vapour deposition) or ALE (atomic layer epitaxy) produced TiO2 cathodes. The charge-discharge cycles were measured with a constant current in the range of 10-6 to 10-5 A for different cells. It was shown that CVD prepared TiO2 cathode is increasing capacity of the cell by allowing higher constant currents to be applied to the cell. The complex impedance measurements of the electrolyte (PEO)4ZnCl2 have been performed in the range of 1 Hz to 1 MHz and in the temperature range from 290 to 400 K by applying Zn or Sn electrodes