| AVS 56th International Symposium & Exhibition | |
| Applied Surface Science | Monday Sessions |
| Session AS+EM+MS+TF-MoA |
| Session: | Spectroscopic Ellipsometry II |
| Presenter: | K. Järrendahl, Linköping University, Sweden |
| Authors: | K. Järrendahl, Linköping University, Sweden J. Landin, Linköping University, Sweden H. Arwin, Linköping University, Sweden |
| Correspondent: | Click to Email |
Ellipsometry is a valuable tool for general materials characterization but also for optical investigations of complex structures including multilayers, photonic crystals, metamaterials and other artificial materials. The complexity of these kind of structures has during the years promoted the use of spectroscopic, variable angle, generalized and Muller-matrix ellipsometry. In parallel more complex optical models and analysis algorithms have come into use.
Naturally occurring structures may show even higher complexity than artifical structures but with a more narrow range of constituent materials, mainly chitin and various proteins. Many interesting structures are found in insects, especially in butterflies and beetles. Fascinating reflection properties result from intricate photonic structures in their wing scales and cuticles. Currently there is a large interest to explore such functional supramolecular architectures for exploitation in nanotechnology.
Even though the optical properties of natural structures are frequently investigated, ellipsometry rarely has been used to reveal structural and optical properties. In this study, Mueller-matrix spectroscopic ellipsometry is applied in the spectral range of 300 to 1700 nm to investigate structures in the cuticle of Scarab beetles, primarily Cetonia aurata (the rose chafer). The cuticle of Cetonia aurata is green with a metallic look and reflects circular polarized light. It has been suggested that the circular polarization of this metallic gloss is caused by a helical structure in the chitinous cuticle. We find that the circular polarization effect is limited to the narrow spectral range 470-550 nm and for shorter or longer wavelengths the reflection properties are similar to those from a near-dielectric material. Furthermore, the light reflected from Cetonia aurata is left-handed circularly polarized and the beetle thus appears black if viewed through a right-handed circular polarizer. In addition to Mueller-matrix spectroscopic ellipsometry, reflectance and scattering measurements are used to characterize the cuticle of Cetonia aurata. Model calculations and parameterization of the nanostructure employing a heliocoidal structure are discussed.