Role of deposition parameters on the SERS applications of Cu and CuO thinfilms fabricated by DC Magnetron Sputtering

Copper (Cu) and Copper Oxide (CuO) thin films were fabricated using a DC Magnetron Sputtering technique. Sputtering parameters such as oxygen to argon gas flow ratio and substrate temperature etc are varied to observe the changes in the structural, optical and morphological properties of the fabricated films. The structural characterization using X-ray diffraction (XRD) confirmed the polycrystalline to monoclinic phase transition in the CuO films. UV-Visible absorption spectroscopy revealed a noticeable shift of absorption peak and bandgap tuning of the CuO films. Field emission scanning electron microscopy images reveal a clear evolution in morphology from densely packed nanoparticles (NPs) to uniform and finer CuO grains in the films fabricated under different substrate temperatures. Raman spectra of the CuO samples indicated the formation of CuO phases and the structural evolution of the CuO peaks with deposition temperature and also indicate the existence of defect states in CuO films influenced by substrate temperature. Transmission electron microscopy (TEM) images and the respective electron diffraction patterns reveal the formation of CuO NPs and the structural phases in CuO films. These Cu and CuO films were utilized for Surface enhanced Raman spectroscopic (SERS) activity using Rhodamine6G dye molecules of various concentrations and observed that the SERS enhancement, which strongly depends on the CuO film’s structure, morphology and the defect states. Overall, this study experimentally demonstrated the relation between charge transfer induced SERS enhancement from the analyte adsorbed and established that the sputtered CuO films as a promising, low-cost, large area and tunable material for SERS based sensing applications.