Extinction Spectra and Electric Near-Field Distribution of Mn Nano-Rod Based Sculptured Thin Films: Experimental and Discrete Dipole Approximation Results

• Published in: Plasmonics (Norwell, Mass.) Mass.), 2015-08, Vol.10 (4), p.861-872
• Main Authors: Siabi-Garjan, A., Savaloni, H.
• Format: Article
• Language: English
• Subjects: Biochemistry; Biological and Medical Physics; Biophysics; Biotechnology; Chemistry; Chemistry and Materials Science; Nanotechnology
• ISSN: 1557-1955; 1557-1963
• DOI: 10.1007/s11468-014-9873-2

Mn columnar (nano-rod shaped) sculptured thin films including helical square, helical rectangle, and helical pentagon with different dimensions were deposited on glass substrates, using oblique angle deposition technique (OAD) together with the rotation of the substrate holder about its surface normal. Field emission electron microscope (FESEM) was used for the structural analysis. Optical spectra of the samples were measured using single beam spectrophotometer for both s- and p-polarized lights and at different incident light angles and different azimuthal angles. The discrete dipole approximation (DDA) method is used to obtain the extinction spectra for nano-rods positioned at different orientations with respect to the incidence light direction. The electric near-field distributions were also investigated for these structures. Results showed that the experimental extinction spectra of structures consisting of a combination of nano-rods (e.g., square, rectangle, and pentagon in this work) are due to overlap of spectra of single nano-rods. It is found that when the electric field of the incident light is parallel or normal to the long axis of the nano-rod, the extinction is maximized or minimized, respectively. Theoretical DDA calculations showed that the latter effect is due to entrapment of light when its electric field is normal to the nano-rod axis.