Infrared optical properties of mixed-phase thin films studied by spectroscopic ellipsometry using boron nitride as an example

Authors

Mathias Schubert, University of Nebraska-LincolnFollow
B. Rheinlander, University of Leipzig
E. Franke, Institute of Surface Modification, Permoserstrasse 15, D-04303 Leipzig, GermanyFollow
H. Neumann, Institute of Surface Modification, Permoserstrasse 15, D-04303 Leipzig, Germany
T. E. Tiwald, University of Nebraska-Lincoln
John A. Woollam, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

11-15-1997

Comments

Published in PHYSICAL REVIEW B VOLUME 56, NUMBER 20, 15 NOVEMBER 1997-II. © 1997 The American Physical Society. Used by permission.

Abstract

We present a microstructure-dependent anisotropic infrared-optical dielectric function model for mixed-phase polycrystalline material from which we derive the transverse and longitudinal-optical modes observable in thin films. Infrared ellipsometry over the wavelength range from 700 to 3000 cm^-1 is then used to determine the phase and microstructure of polycrystalline and multilayered hexagonal and cubic boron nitride thin films deposited by magnetron sputtering onto (100) silicon. The ellipsometric data depend on the thin-film multilayer structure, the layer-phase composition, and the average orientation of the hexagonal grain c axes. In particular, we demonstrate the existence of spectral shifts of longitudinal optical phonons as a function of microstructure, i.e., the average grain crystallographic orientation within the mixed-phase material.