Session: Research Posters

Paper Number: 120069

120069 - Optical Characterization and Modeling of Polycrystalline Moo3 Films Fabricated by Pulsed Laser Deposition 

Molybdenum compounds have gained attention over the past few decades due to their optical, electrical, and thermal properties. Their low cost, abundance, and high chemical stability make them promising materials for the manufacturing industries of optoelectronic devices. Crystalline MoO₃ has three polymorphs: α-MoO₃, a stable orthorhombic phase; β-MoO₃, a metastable monoclinic phase; and h-MoO₃, a metastable hexagonal phase. Recently, α-MoO₃, as a biaxial Van der Waals (vdW) material, has been discovered to support phonon polaritons with in-plane hyperbolic and elliptic dispersion, positioning it at an advantageous stage for manipulating light at the nanoscale. Thin planar films are preferred for integration into photonics platforms for flat optics. Despite the huge potential of α-MoO₃ in optical applications, the development of α-MoO₃-based photonics is hampered by the limited availability of single-phase, oriented, large-area α-MoO₃ films. Pulsed laser deposition (PLD) provides a solution for preparing large-scale thin film MoO₃ with controllable fabrication parameters such as ablation time, laser fluence, and temperature. However, the crystalline structure and morphology highly depend on the deposition conditions.

 

In this work, MoO₃ films deposited by pulsed laser deposition (PLD) on quartz substrates with different fabrication temperatures are characterized using a Fourier transform infrared interferometer. The optical characterization is carried out in reflection mode with incidence angles of 10° and 45°. A linear polarizer is used to generate TE or TM incidence. Despite X-ray diffraction (XRD) indicating that the PLD-prepared MoO₃ films are polycrystalline and exhibit only the orthorhombic α phase, the optical characterization does not reveal any anisotropic features. Instead, the polarization-dependent reflectance can be modeled using an isotropic Lorentz model with fitted oscillator parameters. The resonance frequencies and damping coefficients have been modified compared to the dielectric function of crystalline α-MoO₃. These shifts may be the result of the coupling effect between optics axes in various orientations and the inclusion of air pores. Specifically, a polarization-independent perfect absorption is observed at 972 cm^-1 for a wide angular incidence, and a reflection peak at 1006 cm^-1 is noticed with a high resonance Q-factor. Due to the low fabrication cost, ability to be fabricated in large-scale, and high resonances in the mid-infrared range, the polycrystalline MoO₃ film may find applications in sensors, filters, thermal emitters, and label-free biochemical sensing devices. Nevertheless, this preliminary optical characterization and dielectric function modeling provide insightful indications regarding the crystalline structure of the MoO₃ films and offer a useful study on the feasibility of preparing crystalline MoO₃ films using PLD.

Presenting Author: chiyu yang georgia Institute of Technology

Presenting Author Biography: Chiyu Yang is a Ph.D. candidate at the Georgia Institute of Technology. His research interests include thermal radiation, nanoscale heat transfer, and photonics.

Authors:

chiyu yang georgia Institute of Technology
Zhuomin Zhang Georgia Institute of Technology
Maria Cristina Larciprete Sapienza Università di Roma
Marco Centini Sapienza Università di Roma
Roberto Macaluso Università degli Studi di Palermo
Mauro Antezza University of Montpellier