Nonlinear Optical Properties of SnO₂/Cu/SnO₂ Composite Films Based on Z-Scanning Tests

As a transparent conductive oxide material, tin oxide (SnO2) shows great potential for applications in photoelectronic devices, photocatalysis and photoelectric detection due to its excellent photoelectric properties and chemical stability. In this work, magnetron sputtering was used to successfully create SnO2 nanofilms and SnO2/Cu/SnO2 composite films. Using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), ultraviolet-visible absorption spectroscopy (UV-Vis), and the Hall Effect method, the effects of preparation parameters on the films' morphology, structure, and linear absorption characteristics were described and examined. Moreover, the open-aperture Z-scan technique was used for thoroughly examining the films' nonlinear optical characteristics. The experimental findings demonstrate that as the metal layer's sputtering power increases, the optical bandgap of the SnO2/Cu/SnO2 composite films reduces. When compared to the pure SnO2 films, the composite films' free carrier concentration was noticeably higher. The Z-scan results showed that both the SnO2 films and the SnO2/Cu/SnO2 composite films exhibited the nonlinear absorption property of reverse-saturation absorption, and the sputtering power of both SnO2 and Cu had an effect on the intensity of their reverse-saturation absorption. In addition, the nonlinear absorption intensity of the samples is also affected by the incident laser intensity. The nonlinear optical response of SnO2 nanomaterials can be effectively enhanced by introducing the composite structure, which provides new possibilities for the application of SnO2-based photoelectronic devices.