Growth of thin films by pulsed laser deposition – fundamentals and applications

Prof. Dr. Thomas Lippert

Thin films of organic, polymeric, biological, and inorganic thin films are utilized in many applications, e.g. catalysis, microelectronics, sensors, food industry, tools, optics, decorative coatings, and renewable energy applications, etc.. The preparation of these thin films can be achieved with a variety of tools, ranging e.g. from chemical to physical vapor deposition methods (PVD). One PVD method which is used extensively in research, especially for oxides, but recently also in industry in pulsed laser deposition (PLD). It is noteworthy, that it is often assumed, without further analysis, that the films will have automatically the same composition as the target, which is not really the case. I will show, that all steps and the associated parameter, such as background gas type and pressure, target composition, and substrate type and temperature have a pronounced effect on the PLD process, and therefore on the film composition and properties. The sum of all these effects suggests, that in many cases it can be difficult and time-consuming to find conditions to achieve the desired film composition (properties).

The application of thin films as model systems for renewable energy applications will be briefly shown for two topics, i.e. photocatalysis and ion conduction. Pulsed reactive crossed beam laser ablation (PRCLA), a modification of PLD, is used to obtain oxynitride films. Oxynitrides have gained a lot of attention over the last decade due to their photocatalytic properties using visible light. We utilize photoelectrocatalytic measurements (PEC) to study the oxynitride thin films, mainly LaTiOxNy, where we could show that the crystalline orientation has a pronounced influence on the activity. For ion conductors, we are looking mainly at the influence of strain on oxygen and proton conductivity. We could show, that tensile strain will improve conductivity but not by orders of magnitude as reported elsewhere.

Overview D-MATL Seminar 2018