Abstract-Screening effects in metal sculptured thin films studied with terahertz Mueller matrix ellipsometry

• T. Hofmann^{a, b, c, ,} , 
• S. Knight^b, 
• D. Sekora^b, 
• D. Schmidt^b, 
• C.M. Herzinger^d, 
• J.A. Woollam^d, 
• E. Schubert^b, 
• M. Schubert^b, c

• ^a Department of Physics and Optical Science, University of North Carolina at Charlotte, Charlotte, U.S.A
• ^b Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, U.S.A.
• ^c Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
• ^d J.A. Woollam Co. Inc. 645 M Street, Suite 102, Lincoln, NE 68508, U.S.A.
• 
  

http://www.sciencedirect.com/science/article/pii/S0169433216329324

The anisotropic optical dielectric functions of a metal (cobalt) slanted columnar thin film deposited by electron-beam glancing angle deposition are reported for the terahertz (THz) frequency domain before and after the slanted columnar thin film was passivated by a conformal alumina coating. A simple effective medium dielectric function homogenization approach which describes isolated, electrically conductive columns rendering the thin film biaxial (orthorhombic) is used to model the observed optical responses. Upon passivating the slanted columnar thin film with a 3 nm thick alumina film an increase of both the real and the imaginary part of the dielectric function for all major polarizability directions is found and attributed to screening effects within the spatially coherent metal nanocolumns.