Jonas Köhling

• Metal oxides such as zinc oxide have good electrical properties but processing those from solution requires relatively high temperatures (e.g. spray pyrolysis of zinc acetate at ~ 360 °C). This thesis pursues three fundamentally different approaches to lower the process temperature. Tailored organic molecules are used as a post-deposition treatment to passivate surface traps, i.e. hydroxy groups or chemisorbed water, as the first approach. A successful passivation of surface defects improve the electrical properties of the zinc oxide that occur at low process temperatures. Therefore tailored 1,3-diketones, are presented. Their binding towards zinc is studied and their passivating properties of zinc oxide thin-film transistors analyzed. Fluorinated zinc carboxylate derivates are analyzed as novel potential zinc oxide precursors with focus on lower deposition temperatures as a second approach. FTIR (Fourier transform infrared spectroscopy) and TGA (Thermogravimetric analysis) reveal whether a precursor thermally decomposes to zinc oxide and identifies the decomposition temperature. The third approach: High-speed picoliter droplet analysis gives deeper understanding of droplet interactions with the substrate depending on the temperature under real deposition conditions. A novel model for top-view analysis of dynamic and static advancing contact angles and a comprehensive determination of thermodynamic properties like Leidenfrost point, critical heat flux and thermodynamic boiling regimes is presened. Additionally, a novel hovering state of very small droplets above the substrate at room temperature is presented. This state is similar to the Leidenfrost point and enables the deposition of smooth layers at low temperatures (T < 100 °C). Overall, this analysis allows a fast screening for suitable solvent and substrate combinations for the deposition of precursors that are not processable with standard solvents to find beneficial deposition conditions at low temperatures.