Nanorod structure tuning and defect engineering of MoO for high-performance SERS substrates

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Surface-enhanced Raman scattering (SERS) is gaining interest for plasmon-free substrates based on metal oxide semiconductors.
• These substrates utilize semiconductor defects, structure, and morphology for Raman signal enhancement, avoiding noble metal nanoparticles.
• Molybdenum oxide (MoO₂) is explored as a promising material for fabricating efficient SERS substrates.

Purpose of the Study:

• To fabricate and optimize molybdenum oxide-based SERS substrates using reactive DC magnetron sputtering.
• To investigate strategies for enhancing Raman signal amplification through controlled material properties.
• To evaluate the substrate's performance in detecting low concentrations of target molecules.

Main Methods:

• Fabrication of MoO₂ SERS substrates via reactive DC magnetron sputtering.
• Control of nanorod structure, oxygen deficiency, phase composition, and optical properties by adjusting sputtering and annealing times.
• Characterization using X-ray Diffraction (XRD), Photoluminescence (PL), and Raman spectroscopy.

Main Results:

• Optimized fabrication conditions yielded MoO₂ SERS substrates with controllable nanorod structures, oxygen defects, and mixed MoO₃/Mo₉O₂₆ phases.
• Enhanced Raman signals were attributed to a combination of chemical (CM) and electromagnetic (EM) mechanisms.
• The MoO₂ substrates achieved a high enhancement factor (EF) of 1.14 × 10⁶ for R6G detection at 0.01 ppm, with a limit of detection (LOD) of 0.01 ppm.

Conclusions:

• Tailoring sputtering and annealing parameters allows precise control over MoO₂ nanostructure and defect engineering for SERS applications.
• The developed MoO₂ SERS substrates exhibit excellent sensitivity, reproducibility, and temporal stability for trace molecule detection.
• Plasmon-free MoO₂ nanostructures offer a viable and efficient platform for advanced chemical sensing.