Physical and chemical vapour deposition
In the area of solid oxide fuel cells (SOFCs), ceramic high-temperature fuel cells are investigated as a future energy conversion technique. Research and development range from the synthesis of suitable materials and the production of components using powder technology, including qualified characterization, to complete fuel cells.
Microstructured, more powerful, and less expensive: The microelectronics industry has demonstrated how highly complex systems with production methods suitable for mass production can be improved and become more affordable. Efficient and in turn, economical production is also a very important aspect for fuel cells and other energy converters and storage systems.
For this reason, IEK-1 uses so-called vapour deposition. There are two different types of vapour deposition: physical vapour deposition (PVD) and chemical vapour deposition (CVD).
With physical vapour deposition (PVD), a material is converted to the gas phase by evaporation or sputtering on an atomic scale. The gas hits the samples to be coated and depending on the duration of the experiment, is deposited there as a nanometre-to-micrometre-thick layer. During the entire coating process–conversion to the gas phase, movement to the samples and condensation on the surface of the sample–only the aggregate state of the material changes: from "solid" or "liquid" to "gaseous" and back to "solid". However, in terms of chemistry, it basically remains the same material.
This is different for chemical vapour deposition (CVD). With this method, gases are guided to the samples, which undergo a chemical reaction on the way to the sample or on the surface of the sample. Part of the substances which have undergone the chemical reaction remains on the surface and forms the layer.
For physical vapour deposition, the Institute of Energy and Climate Research (IEK-1) has facilities for cathode atomizing ("sputtering") in direct current (DC), in pulsed and in radio frequency (RF) operation, as well as electron-beam evaporation. Both processes can also be carried out in a reactive manner, meaning in the presence of a gas with which the material can react in the gas phase. In order to adjust the morphology, the coating is carried out at temperatures of up to 800 °C and optionally with additional ion assistance.
The facility for chemical vapour deposition allows the use of metal-organic precursors (this method is referred to as MO-CVD), as well as a process flow with which the layers are arranged in atomic layers built on top of each other (atomic layer deposition, ALD).
The use of metal-organic precursors allows relatively low coating temperatures in the range of approx. 100 °C–300 °C to be achieved. The ALD mode also permits coating of interior surfaces of porous materials, allowing, for example, diffusion barriers, oxidation protective coatings, or biocompatible layers to be applied.