2020, Yang, C., Wang, W., Nefedov, A., Wang, Y., Mayerhöfer, T.G., Wo¨ll, C.

The interaction of light with matter at surfaces of dielectrics strongly depends on polarization. Here, we present the first infrared spectroscopic evidence for significant polarization effects in the spectroscopic detection of adsorbate vibrational frequencies. In addition to much larger peak intensities for p-polarized light relative to s-polarization, a small but distinct blue shift was identified for CO adsorbed at the surfaces of two prototype dielectric substrates, CeO2(111) and CaCO3(10.4). A simulation using a layer model yields very good agreement with experiment.

2023, Buchheit, Roman, Niebuur, Bart-Jan, González-García, Lola, Kraus, Tobias

Hybrid dielectrics were prepared from dispersions of nanoparticles with gold cores (diameters from 2.9 nm to 8.2 nm) and covalently bound thiol-terminated polystyrene shells (5000 Da and 11 000 Da) in toluene. Their microstructure was investigated with small angle X-ray scattering and transmission electron microscopy. The particles arranged in nanodielectric layers with either face-centered cubic or random packing, depending on the ligand length and core diameter. Thin film capacitors were prepared by spin-coating inks on silicon substrates, contacted with sputtered aluminum electrodes, and characterized with impedance spectroscopy between 1 Hz and 1 MHz. The dielectric constants were dominated by polarization at the gold-polystyrene interfaces that we could precisely tune via the core diameter. There was no difference in the dielectric constant between random and supercrystalline particle packings, but the dielectric losses depended on the layer structure. A model that combines Maxwell-Wagner-Sillars theory and percolation theory described the relationship of the specific interfacial area and the dielectric constant quantitatively. The electric breakdown of the nanodielectric layers sensitively depended on particle packing. A highest breakdown field strength of 158.7 MV m−1 was found for the sample with 8.2 nm cores and short ligands that had a face-centered cubic structure. Breakdown apparently is initiated at the microscopic maxima of the electric field that depends on particle packing. The relevance of the results for industrially produced devices was demonstrated on inkjet printed thin film capacitors with an area of 0.79 mm2 on aluminum coated PET foils that retained their capacity of 1.24 ± 0.01 nF@10 kHz during 3000 bending cycles.