AVS 63rd International Symposium & Exhibition
    Spectroscopic Ellipsometry Focus Topic Thursday Sessions
       Session EL+AS+BI+EM+TF-ThA

Paper EL+AS+BI+EM+TF-ThA3
Optical Properties of Nanocrystalline Si3N4:TiN Thin Films

Thursday, November 10, 2016, 3:00 pm, Room 104C

Session: Optical Characterization of Nanostructures and Metamaterials (2:20-3:40 pm)/Application of Spectroscopic Ellipsometry for the Characterization of Thin Films (4:00-6:00 pm) and Biological Materials Interfaces
Presenter: Neil Murphy, Air Force Research Laboratory
Authors: N.R. Murphy, Air Force Research Laboratory
L. Sun, General Dynamics Information Technology
J.G. Jones, Air Force Research Laboratory
J.T. Grant, Azimuth Corporation
Correspondent: Click to Email
Nanocomposite films comprised of mixed nitrides, especially Si-Me-N (Me=Ti, Zr, Hf), have generated significant attention due to their robust thermal and mechanical properties. In addition to their desirable structural characteristics, the mixing of dielectric Si3N4 with various metallic nitrides has the potential for the deposition of hybrid thin films with controllable optical absorption based on the fraction of metallic nitrides present within the Si3N4 matrix. In this work, nanocrystalline Si3N­4 thin films, doped with varying amounts of TiN (1-20 at.%), are deposited using reactive magnetron co-deposition. Note that the Berg model for reactive sputtering is utilized to select the initial conditions for the deposition of the films, which are sputtered from elemental targets within a mixed nitrogen-argon environment and characterized in-situ using spectroscopic ellipsometry. The TiN content is varied through systematic adjustment of the current applied to the Ti cathode concurrent with pulsed DC deposition of Si3N4 at a constant current of 0.4 A. The use of ­in-situ­ ellipsometry, interrogating wavelengths from 381-1700 nm, allows for the real-time measurement of the refractive index, extinction coefficient, and thickness of the growing films. Additionally, in-situ ellipsometry data is used to observe the behavior of the films at the onset of growth, indicating the onset of Volmer-weber type nucleation. All ellipsometric data are fit using a Bruggeman effective medium approximation, varying the amount of TiN present within the films. Optical characterization of the Si3N4:TiN thin films indicates that the refractive index at 550 nm decreases gradually from 2.05 to 1.99 as the TiN content is increased from 0-20 at%, while the extinction coefficient rises from 0 to 0.35. These films demonstrate strong absorption features starting from 550 nm out to 1500 nm, allowing for efficient absorption of visible and near-infrared wavelengths. Variation of the TiN content within Si3N4:TiN films allows for the user to select the magnitude of extinction coefficient and refractive index, leading to potential applications as mechanically robust layers in interference filters, or as alternatives to lossy metallic configurations in plasmonic devices.