Coating unit for thin layers

• Subject Area: Biological Chemistry and Food Chemistry
• Term: Funded in 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 422921395

At the Faculty of Chemistry, it is planned to install a coating unit for thin films made of silicon monoxide, silicon dioxide, gold, chromium or titanium. Possible coating techniques are sputtering and electron-beam evaporation. Coated surfaces are the first crucial step in the preparation of biohybride samples like solid supported lipid bilayers, pore spanning membranes, cell membrane fragments and cultivated cell monolayers. The requirements for the coating unit are manifold depending on the application: i) pure and smooth ultrathin films for electron microscopy, electrochemistry and optics; ii) multicomponent films for high stability, adhesiveness, and surface functionalization and iii) orthogonal coating to yield a geometry-specific functionalization. Since gold coatings require an additional adhesive layer of titanium or chromium, the option to coat two consecutive materials without ventilation of the coating unit is mandatory to ensure contamination-free surfaces. Therefore, two sputtering sources or evaporation units with automated systems to change sources would be needed. Coating surfaces with silicon monoxide und gold allows retaining established preparation protocols. However, silicon dioxide has as yet not been possible to be deposited but is required to fully explore fluorescence-based techniques. For example, the effect of fluorescence quenching is greatly diminished compared to gold and silicon monoxide surfaces. Moreover, MIET (metal induced energy transfer) microscopy and acoustic resonators require a thin gold layer underneath the silicon dioxide surface to enable either defined quenching of fluorescence or driving of the oscillator. Since surface roughness and thickness influences the properties of the biomimetic samples, precise control and reproducibility of these parameters is necessary. This can be achieved by automation of the surface coating processes. For advanced fluorescence techniques like MIET, surfaces with a root mean square roughness below one nanometer nm are advantageous to minimize fluorescence enhancement and quenching effects. Furthermore, surface roughness enhances lateral membrane tension in the case of pore spanning membranes, which influences the diffusion of lipids, proteins and lipid domains. Thin metal coatings are also required to ensure rather artefact-free imaging of samples for electron microscopy. To guarantee reproducible preparation of pore spanning membranes, orthogonal surface coatings are required, i.e. only the top surface has to be coated. Very high coating chambers or glancing angle coating procedures can achieve orthogonality of coatings.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Beschichtungsanlage für dünne Schichten
• Instrumentation Group: 8330 Vakuumbedampfungsanlagen und -präparieranlagen für Elektronenmikroskopie
• Applicant Institution: Georg-August-Universität Göttingen
• Leader: Professorin Dr. Claudia Steinem