Transparent Substrates

The video explains the working principle of knife edge illumination and practical handling of nanofilm_knife edge_ep4 setup.

Thin films on transparent substrates are of increasing interest in advanced technologies like flexible displays, plastic solar cells, functional windows or new concepts in illumination. State of the art in thin film metrology is spectroscopic ellipsometry, but transparent substrates are still an issue because of the backside reflected light that after a long pathway through a transparent substrate gets incoherent or partly coherent with the consequence that the phase information gets completely or partly lost and the determination of metrological parameters of the layer of interest is difficult or impossible. A number of workarounds are established to get rid of backside reflection, like mechanical grinder or a number of different treats of the backside with different types of tape, with glues, with toothpaste etc. A number of these approaches are working well but in most cases, the sample cannot be used for further investigations.

The tailored organization of nanoparticles at interfaces is of increasing technical and scientific interest. Silicon-dioxide nanoparticles (SiO₂ NPs) may be used for applications which require transparent surface coatings or functional surface patterns for the visible range of the electromagnetic spectrum, e.g. super-hydrophobic anti-reflection coatings on glass slides¹. In this work, printed line-shaped patterns of aggregates of SiO₂ NPs on glass substrates were characterized by means of spectroscopic imaging ellipsometry and atomic force microscopy (AFM). The determination of the layer-thickness profiles with peak heights on the sub-micron scale was a matter of particular interest. We applied spectroscopic imaging ellipsometry in this proof-ofprinciple study to show that imaging ellipsometry is capable of the characterization of SiO₂ nanoparticle patterns, even on transparent substrates