Microstructural and optical duality of TiO2/Cu/TiO2 trilayer films grown by atomic layer deposition and DC magnetron sputtering

[Display omitted] •A comparative study on the effect of Cu interlayer on optical properties of TiO2(60 nm)/Cu/TiO2(60 nm) trilayers prepared by atomic layer deposition (ALD) was achieved.•Increasing the thickness of the Cu interlayer from 20 to 60 nm decreases the indirect optical Eg from 3.10 to 1.86 eV.•The optical Eg and the electronegativity (χ) were used for determining the optical basicity (Å) and refractive index (n).•The results obtained from TiO2/Cu/TiO2 triple-layer films show that the addition of a Cu interlayer provides a basis for their application in low-cost mid-IR detection. In this research, we report a comparative study of trilayer TiO2(60 nm)/Cu/TiO2(60 nm) thin film as a function of different Cu interlayer thickness (20, 40 and 60 nm), fabricated by atomic layer deposition (ALD) and DC magnetron sputtering. The surface morphology, elemental information and optical properties, were tested as a function of Cu interlayer thickness by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX) and double beam spectrophotometer (UV–vis) respectively.The growth mechanism and the microstructural conversion were investigated. The absorption spectrum was mesured and used to calculate the energy band gap (Eg). The obtained results show that the increase of the Cu interlayer enhance the activity of photocatalysis by employing distinct modification strategies to decrease the indirect optical band gap energy from 2.85 to 1.86 eV, and conventionally making the photocatalyst efficient to absorb visible light range. The role of the optical energy band gap Eg as well as the average electronegativity (χ) as basic parameters of optical basicity (Å) and refractive index (n) has been emphasized. Values of electronegativity (χ), phase velocity (V) and transmission coefficient (TC) decreased, while the refractive index, optical basicity, electronic polarizability (αe), and reflection loss (RL) increased with increasing Cu interlayer thickness. A good agreement is observed among the selected parameters. The results demonstrate that the ALD and the DC magnetron sputtering are promising techniques for preparing TiO2/Cu/TiO2 thin films, with different thickness of copper (Cu), that can be used in low-cost mid-IR detection and can enhanced the properties of optoelectronic devices.