Laser Fabricated Cu₂O-CuO/Ag Nanocomposite Films for SERS Application**

Noble metals are widely used in surface-enhanced Raman spectroscopy (SERS) because of the electromagnetic enhancement, which is from the surface plasma resonance on noble metal surface under the action of an electromagnetic field that can greatly enhance the Raman signal of the molecule. However, high cost limits their widespread use in realistic applications. Therefore, semiconductor nanomaterials have been introduced in SERS substrate. Here, we fabricate Cu₂O-CuO film on glass by direct laser writing and then mix with Ag NWs to form Cu₂O-CuO/Ag nanocomposite substrate. The composite substrate shows strong Raman resonance for both Rhodamine 6G (R6G) and 4-mercaptobenzoic acid (4-MBA), good uniformity and stability. LOD of R6G and 4-MBA is 10⁻¹⁰ and 10⁻⁶ M, respectively. We further discuss the charge transfer process of metal-semiconductor-molecule (Ag-Cu₂O-MBA and Ag-CuO-MBA) and Raman enhancement mechanism with XPS and UV-vis diffuse reflectance spectroscopy validation. This work provides a facile and low-cost method of fabricating Cu₂O-CuO/Ag SERS nanocomposite substrate.