Generalized Ellipsometry on Sculptured Thin Films made by Glancing Angle Deposition

Authors

Daniel Schmidt, University of Nebraska-LincolnFollow

First Advisor

Eva Schubert

Second Advisor

Mathias Schubert

Date of this Version

12-2010

Document Type

Article

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Interdepartmental Area of Engineering (Electrical Engineering), Under the Supervision of Professors Eva Schubert and Mathias Schubert. Lincoln, Nebraska: December 2010
Copyright 2010 Daniel Schmidt

Abstract

In this thesis, physical properties of highly optically and magnetically anisotropic metal sculptured thin films made by glancing angle deposition are presented. Predominantly, the determination of optical and magneto-optical properties with spectroscopic generalized Mueller matrix ellipsometry and homogenization approaches is discussed. Nomenclatures are proposed to unambiguously identify the sculptured thin film geometry.

Generalized ellipsometry, a non-destructive optical characterization technique, is employed to determine geometrical structure and anisotropic dielectric properties of highly spatially coherent three-dimensionally nanostructured thin films in the spectral range from 400 to 1700 nm. The analysis of metal slanted columnar thin films (F1-STFs) deposited at glancing angle (θ_i = 85°) revealed monoclinic optical properties of such nanostructures, and the optical response can be modeled with a single homogeneous biaxial layer. This homogeneous biaxial layer approach is universally applicable to F1-STFs and effective optical properties of the nanostructured thin films are attained.

More complex sculptured thin films, which can be engineered by a dynamic in-situ substrate rotation, may be considered as cascaded F1-STFs. A piecewise homogeneous biaxial layer approach is described, which allows for the determination of principal optical constants of chiral multi-fold and helical sculptured thin films. For optical analysis, complex sculptured thin films can be virtually separated into their F1-STF building blocks. It is confirmed that such sculptured thin films have modular optical properties. This characteristic can be exploited to predict the optical response of sculptured thin films grown with arbitrary sequential substrate rotations.

Magneto-optical generalized ellipsometry in the polar and longitudinal Kerr geometry is utilized to determine the spectral magneto-optical response of Co F1-STFs and estimate the magnetization direction. Kerr effect measurements and calculations reveal a strong azimuthal dependence with peak Kerr rotation one order of magnitude larger than what has been reported for solid Co thin films. The concept of generalized ellipsometry in conjunction with a three-dimensional vector magnet is introduced and first measurement results presented.