Using a Au/pitted a-plane GaN substrate to aggregate polar molecules for highly efficient surface-enhanced Raman...

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Developing efficient surface-enhanced Raman scattering (SERS) substrates is crucial for sensitive molecular detection.
• Existing methods often require complex fabrication processes like etching or lithography.

Purpose of the Study:

• To create a novel SERS substrate using metal-organic chemical vapor deposition (MOCVD) for direct growth of pitted GaN films.
• To evaluate the SERS performance of the Au-coated pitted GaN substrate for molecular detection.

Main Methods:

• Direct growth of pitted a-plane GaN thin films using MOCVD.
• Deposition of a thin gold (Au) layer (∼25 nm) onto the pitted GaN surface.
• Characterization of SERS performance using Rhodamine 6G (R6G) and methylene blue as probe molecules.

Main Results:

• The substrate achieved a low limit of detection (∼10⁻⁹ M) for R6G with a high enhancement factor (4.27 × 10⁸).
• Raman spectral mapping revealed molecular localization within the micrometer-sized pits, particularly for polar molecules.
• The polarity of Ga and N atoms in the pits was identified as key for efficient polar molecule aggregation.

Conclusions:

• The developed pitted GaN/Au SERS substrate offers a simplified fabrication process and high detection sensitivity.
• The pit-induced molecular localization is effective for polar analytes, showing potential for biomedical applications.
• Further optimization of Au layer thickness could enhance SERS performance and molecular localization effects.