TiN-Au/HfO₂-Au Multilayer Thin Films with Tunable Hyperbolic Optical Response.

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Hyperbolic metamaterials (HMMs) exhibit anisotropic properties and tunability, making them suitable for integrated photonic devices.
• HMMs can be fabricated as multilayer or vertically aligned nanocomposites (VAN).

Purpose of the Study:

• To demonstrate self-assembled HfO2-Au/TiN-Au multilayer thin films combining multilayer and VAN designs.
• To investigate the tunable anisotropic physical properties of these novel HMM structures.
• To explore the transformation between Type I and Type II optical hyperbolic dispersion.

Main Methods:

• Fabrication of HfO2-Au and TiN-Au VAN structures using pulsed laser deposition (PLD).
• Controlled adjustment of HfO2 and TiN layer thicknesses via laser pulses.
• Characterization of optical hyperbolic dispersion properties.

Main Results:

• Achieved tunable anisotropic physical properties by adjusting bi-layer thickness and number of bi-layers.
• Demonstrated transformation from Type II to Type I optical hyperbolic dispersion by varying layer thickness (e.g., 20 nm to 4 nm).
• Successfully combined multilayer and VAN designs in a three-phase HMM structure.

Conclusions:

• The novel three-phase VAN HMM structure offers significant potential for tailorable optical components.
• This metamaterial design is promising for future integrated photonic devices.
• Tunability of optical properties through structural control is a key advantage.